Dissertations / Theses: 'Polymyxin E'

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Koch, Peer-Joachim. "Untersuchungen zur Wechselwirkung von Polymyxin B mit bakteriellen Lipopolysacchariden." [S.l.] : [s.n.], 1998. http://www.diss.fu-berlin.de/1998/22/index.html.

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2

Saohin, Wipawee. "Studies on the stability and activity of polymyxin B solutions." Thesis, Robert Gordon University, 1997. http://hdl.handle.net/10059/606.

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The correlation between the chemical stability and the microbiological activity of polymyxin B in phosphate buffer pH 6.0 and in proprietary eye drops was evaluated. High Performance Liquid Chromatography (HPLC) was used to quantify the amount of the main components in samples stored at 43,50,55 and 60°C for a period of 500 h. The data indicated that there are significant differences in chemical stability among the different proprietary eye drops. The accurate decomposition rate constants and shelf-lives (~o) at 4°C of two of the six formulated eye drops and the standard polymyxin B solution stored in glass containers at pH 6.0 were established. It was concluded that microbiological assay by agar diffusion was unsuitable for determining the activity of control polymyxin B in phosphate buffer and polymyxin B in eye drops. Killing time determinations for polymyxin B against cell suspensions of P. aeruginosa NCTC 6750 were consequently used. Thioglycollate broth containingp- aminobenzoic acid (PABA) 0.16 %w/v and magnesium sulphate 1 %w/v was used as an inactivating recovery medium. The effect of preservatives and of second antibacterials contained in the eye drops were tested individually and combined with polymyxin B. Thiomersal 0.001 %w/v, trimethoprim 0.02 %w/v and thiomersal 0.001 %w/v plus trimethoprim 0.02 %w/v did not have an effect on the activity of polymyxin B 2000 U/ml. Neomycin was an exception and at the concentrations in the range 0.0192 to 0.16 %w/v exhibited an antagonistic effect. Chemical interaction between polymyxin B and neomycin could not be detected and it was considered that the inhibitory effect of neomycin may be the result of competition between polymyxin B and neomycin for the same binding sites on the cell surface. Gentamicin is active against P. aeruginosa NCTC 6750 and at concentrations of 0.075 and 0.036 %w/v it exhibited an additive effect with polymyxin B 2000 U/ml against the test organism. The results obtained with the samples stored at 55°C for a period of 500 h demonstrated the critical effect of pH. At a pH of 6.0 microbiological activity and chemical stability appeared optimal. The chemical stability data of five eye drop samples correlated with microbiological activity data. Exceptions were polymyxin B in one eye drop sample and control polymyxin B. These extensively decomposed samples showed good antibacterial activity which appeared to result from the activity of decomposition products. Chemical stability data for standard polymyxin B solution at pH 6.0 also correlated to microbiological activity data over the temperature range of 92 - 115°C. The polymyxin B retained detectable microbiological activity when the amount of PB1 was greater than 20%. It is suggested that the decomposition products which occurred at these higher temperatures did not possess antibacterial activity.

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Rudilla, Mateo Héctor. "Synthetic Polymyxin-based Peptides Against Multidrug Resistant Bacteria: A Therapeutic Option." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668033.

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Pseudomonas aeruginosa and Staphylococcus aureus are nosocomial opportunistic pathogens causing a wide variety of both acute and chronic infections, such as pneumonia, bacteraemia, and urinary tract infections. Immunocompromised patients and those suffering cystic fibrosis show a particularly high susceptibility to infection by these microorganisms. Moreover, the increasing frequency of the isolation of multidrug-resistant bacteria (MDR) is a major cause for concern. Polymyxins are cyclic peptides with antimicrobial action against Gram-negative bacteria that have been available since 1949, although they were left largely unused during the seventies because of their nephrotoxicity and the availability of less toxic antimicrobials to which bacteria had not yet developed resistance. The most known polymyxin is colistin; like other cationic polypeptides, colistin is an amphipathic compound and, it is believed that this amphipathic nature is relevant to its activity against bacteria. Hence, the aim of this thesis was to synthesize antimicrobial peptides inspired in colistin scaffold and explore their antimicrobial activity against multidrug resistant bacteria such as P. aeruginosa and S. aureus, determine possible synergistic interactions with commercial antibiotics and explore their mechanisms of action. Synthesis: The main attempt in this first part was to synthesize peptides in solid phase by the Fmoc/tBu method. After synthesis, peptides were purified by preparative HPLC method and finally, peptides were characterized by MALDI-TOF. Antimicrobial activity: This part focused on the study the antimicrobial capacity of our peptides against multidrug resistant bacteria, specially P. aeruginosa and S. aureus. First peptide (AMP38) showed an acceptable antimicrobial activity against P. aureuginosa. Moreover, several imipenem-resistant P. aeruginosa were tested with AMP38 and imipenem showing a quite considerable synergistic action, both with planktonic and sessile bacteria. In addition, two peptides of the same family (CAMP113 and CAMP207) were tested against S. aureus (both planktonic and sessile) showing a surprising antimicrobial action since Gram- positive bacteria are regarding as naturally resistant to polymyxins. Moreover, these peptides showed an inordinately high selectivity index. Mechanisms of action: The final part of this doctoral thesis focused on an initial exploration of mechanisms of action of peptides above mentioned. Transmission electronic microscopy (TEM) assays were performed in order to elucidate possible interactions between peptides and outer membrane of Gram-negative bacteria. In addition, isothermal titration calorimetry assays were carried out to determine peptide-teichoic acid interactions. Data obtained from these studies are promising, being able to be a therapeutic alternative for infections produced by multidrug resistant bacteria.
Pseudomonas aeruginosa y Staphylococcus aureus son patógenos nosocomiales oportunistas causantes de una gran variedad de infecciones tanto crónicas como agudas, tales como neumonía, bacteriemia e infecciones del tracto urinario. Los pacientes inmunocomprometidos y aquellos que padecen fibrosis quística muestran una susceptibilidad particularmente alta a infectarse por estos microorganismos. Además, la mayor frecuencia de aislamientos de P. aeruginosa y S. aureus resistentes a múltiples fármacos (MDR) es una causa importante de preocupación. Las polimixinas son péptidos cíclicos con capacidad antibiótica contra las bacterias Gram- negativas que han estado disponibles desde 1949, aunque se dejaron en gran parte de usar durante los años setenta debido a su nefrotoxicidad y a la disponibilidad de otros antimicrobianos menos tóxicos a los cuales las bacterias aún no habían desarrollado resistencias. La polimixina más conocida es la colistina e, igual que otros polipéptidos catiónicos es un compuesto anfipático. Se cree que esta naturaleza anfipática es relevante en su actividad contra las bacterias. Por lo tanto, el objetivo de esta tesis fue sintetizar péptidos antimicrobianos inspirados en el esqueleto molecular de la colistina y explorar su actividad antimicrobiana contra bacterias resistentes a múltiples fármacos como P. aeruginosa y S. aureus, determinar posibles interacciones sinérgicas con antibióticos comerciales y realizar un primer acercamiento a sus mecanismos de acción. SÍNTESIS: El principal objetivo de esta primera parte fue sintetizar los péptidos en fase solida por el método Fmoc/tBu. Después de la síntesis, los péptidos se purificaron por el método de HPLC preparativo y, finalmente los péptidos se caracterizaron por MALDI-TOF. ACTIVIDAD ANTIMICROBIANA: Esta parte se centró en el estudio de la capacidad antimicrobiana de nuestros péptidos contra bacterias multirresistentes, especialmente P. aeruginosa y S. aureus. El primer péptido (AMP38) mostró una actividad antimicrobiana aceptable frente a P. aeruginosa. Además, se probaron varias cepas de P. aeruginosa resistentes a imipenem con AMP38 mostrando una actividad sinérgica bastante considerable, tanto en bacterias planctónicas como sésiles. Adicionalmente, se realizaron ensayos con dos péptidos de la misma familia (CAMP113 y CAMP207) frente a S. aureus (tanto planctónicos como sésiles) mostrando una acción antimicrobiana sorprendente, ya que las bacterias Gram-positivas como S. aureus se consideran naturalmente resistentes a las polimixinas. MECANISMOS DE ACCIÓN: La parte final de esta tesis doctoral se centró en una exploración inicial de los mecanismos de acción de los péptidos mencionados anteriormente. Se realizaron ensayos de microscopía electrónica de transmisión (TEM) para aclarar las posibles interacciones entre los péptidos y la membrana externa de las bacterias Gram-negativas. Además, se realizaron ensayos de calorimetría de titulación isotérmica para determinar las interacciones péptido-ácido teicoico. Los datos obtenidos de estos estudios son prometedores, pudiendo ser una alternativa terapéutica para las infecciones producidas por bacterias resistentes a múltiples fármacos.

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Hayashi, Satoko. "Enrichment of Salmonella in poultry for detection by polymyxin-cloth enzyme immunoassay." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0031/MQ27064.pdf.

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Hayashi, Satoko Carleton University Dissertation Biology. "Enrichment of salmonella in poultry for detection by polymyxin-cloth enzyme immunoassay." Ottawa, 1997.

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6

Onaca, Ozana Simina [Verfasser]. "Functionalized polymer vesicles and interactions with Polymyxin B and derivatives / Ozana Simina Onaca." Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2008. http://d-nb.info/1034967282/34.

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Gatzeva-Topalova, Petia Z. "Biophysical and biochemical characterization of ArnA: A required enzyme in the polymyxin resistance pathway." Diss., Connect to online resource, 2005. http://wwwlib.umi.com/cr/colorado/fullcit?p3190368.

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Wang, Haiyan Carleton University Dissertation Biology. "The Polymyxin-cloth enzyme immunoassay for detection of Salmonellae and its confirmation by polymerase chain reaction." Ottawa, 1995.

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9

Chacra, Nádia Araci Bou. "Suspensão oftálmica de dexametasona e polimixina B: formulação e avaliação da eficácia antimicrobiana de conservantes." Universidade de São Paulo, 1994. http://www.teses.usp.br/teses/disponiveis/9/9139/tde-10072008-164932/.

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Suspensões oftálmicas de dexametasona e polimixina B foram formuladas variando-se os conservantes e combinando 2 concentrações de polissorbato 20 e hidroxipropilmetilcelulose segundo o projeto fatorial 2n. A estabilidade das preparações foi avaliada através de parâmetros físicos, com ênfase na facilidade de rehomogeneização após período de repouso. Das 16 fórmulas foram selecionadas 8 para avaliação da eficácia antimicrobiana do sistema conservante pelo método de desafio, segundo B.P. 88, frente a Pseudomonas aeruginosa, Pseudomonas cepacia e Sthaphylococcus aureus. O ensaio foi precedido de validação da técnica segundo planejamento estatistico two way e split + plot. Os produtos contendo associação clorhexidina e álcool feniletílico atenderam às exigências do compêndio adotado, em oposição aos sistemas contendo cloreto de benzalcônio e EDTA, além de clorhexidina e EDTA, independente da concentração do tensoativo e agente suspensor.
Ophthalmic suspensions of dexametasone and polymyxin B were formulated varying the preservatives and combining two concentrations of polysorbate 20 and hydroxypropylmethylcellulose according to the factorial project 2n. The stability of the preparations were evaluated through physical parameters, with emphasis on the easing of the rehomogenization after a period of rest. 8 of the 16 formula were selected for an evaluation of the antimicrobial efectiveness of the preservative system through the challenge method, according to B.P. 88, against Pseudomonas aeruginosa, Pseudomonas cepacia and Sthaphylococcus aureus. The test was preceded by a validation of the technique according to statistical planning two way and split + splot. The products containing the association of chorhexidine and phenylethyl alcohol complied to the requirements of the adopted compendium, in opposition to the systems containing benzalkonium chloride and EDTA, besides clorhexidine and EDTA, not depending on the concentration of the surfactant and suspending agents.

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10

Luz, Daniela Inocente. "Heterorresistência e resistência adaptativa à Polimixina B em isolados de Enterobacteriaceae produtores de Klebsiella pneumoniae carbapenemase (KPC)." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/115008.

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As enterobactérias constituem importantes agentes causadores de infecções nosocomiais e possuem alta capacidade em adquirir mecanismos de resistência, inclusive aos carbapenêmicos, que são os principais fármacos utilizados para o tratamento das infecções causadas por esses microrganismos. Assim, as opções terapêuticas tornaram-se restritas e as polimixinas (polimixina B e colistina) voltaram a ser utilizadas na prática clínica. Estudos descrevem a ocorrência de heterorresistência à colistina em enterobactérias. Para a resistência adaptativa, não há relatos atuais para enterobactérias frente à polimixina B. O objetivo deste trabalho foi avaliar a presença destes dois fenômenos de resistência à polimixina B, e sua estabilidade, em isolados de Enterobacteriaceae produtores de Klebsiella pneumoniae carbapenemase (KPC), provenientes de pacientes hospitalizados. A avaliação da heterorresistência foi feita através da análise do perfil populacional (PAP) em 8 isolados de enterobactérias, inoculando-se diluições seriadas dos mesmos em Agar Mueller Hinton contendo diferentes concentrações de polimixina B. Os ensaios de resistência adaptativa foram realizados para os mesmos isolados, submetendo-os ao cultivo em concentrações crescentes de polimixina B. A determinação da estabilidade das subpopulações resistentes foi feita através de passagens dos isolados, por 4 dias consecutivos, em meio livre de antibiótico, e posterior determinação da CIM. A CIM foi reavaliada após 2 e 6 meses de estocagem a -80ºC para os isolados com subpopulações heterorresistentes ou com resistência induzida. Realizou-se técnica de tipagem molecular (PFGE), entre as populações originais e respectivas subpopulações resistentes. Foram avaliados 4 isolados de Klebsiella pneumoniae caracterizadas como 4 clones distintos (K1, K2, K3 e K4), assim como os 3 isolados de Enterobacter cloacae - 2 de clone idêntico (Ec1a e Ec1b), mas com perfis fenotípicos distintos e um clonalmente distinto (Ec2), e uma cepa de Escherichia coli (E1). As CIM iniciais para polimixina B, realizadas por microdiluição em caldo, foram entre 0,0625 e 0,25 μg/mL. Quatro amostras demonstraram heterorresistência (K1, K2, K3 e K4), as quais cresceram nas concentrações 2 (K2), 3 (K1, K4) e 6 μg/mL (K3), e suas CIM após 4 dias de passagem em meio livre de antibiótico se mantiveram altas (K1 4 μg/mL, K2 e K3 16 μg/mL e K4 2 μg/mL). As subpopulações heterorresistentes representaram 0,000087% a 0,00036% de suas populações originais. Três amostras demonstraram resistência adaptativa (K1, K3 e K4), as quais cresceram até concentração 64 μg/mL de polimixina B, e a CIM após 4 dias de passagem em meio livre de antibiótico foi de 32 μg/mL para os três isolados. As CIM mantiveram-se elevadas após 2 e 6 meses de estocagem, tanto para os isolados heterorresistentes como para aqueles da indução da resistência. Por PFGE, verificou-se a relação clonal entre os isolados clínicos iniciais e as subpopulações resistentes. Dos 8 isolados estudados, 4 apresentaram heterorresistência e 3 apresentaram resistência adaptativa. A avaliação da CIM após 2 e 6 meses demonstrou estabilidade das subpopulações, sugerindo o envolvimento de mecanismos moleculares para ambos os fenômenos. Estudos moleculares devem ser realizados para melhor avaliação da heterorresistência e da resistência adaptativa, e melhor compreensão do significado clínico e implicações terapêuticas destes dois fenômenos.
Enterobacteriaceae representants are important agents of nosocomial infections and have high capacity to acquire mechanisms of resistance, including carbapenems, which are the major drugs used for the treatment of infections caused by these microorganisms. Thus, treatment options become limited and polymyxins (polymyxin B and colistin) were again used in clinical practice. Studies describe the occurrence of heteroresistance to colistin in Enterobacteriaceae For adaptive resistance, there are no current reports for those microorganisms front of polymyxin B. The purpose of this study was to evaluate the presence of these two phenomena of resistance to polymyxin B, and its stability in isolates of Enterobacteriaceae Klebsiella pneumoniae carbapenemase (KPC) producing, from hospitalized patients. The evaluation of heteroresistant was made by examining the population profile (PAP) of 8 isolates of enterobacteria inoculating serial dilutions thereof in Mueller Hinton agar containing different concentrations of polymyxin B. The adaptive resistance tests were performed for the same isolates by subjecting them to growing in increasing concentrations of polymyxin B. The determination of the stability of resistant subpopulations was performed after daily sub-cultured in antibiotic-free medium for 4 consecutive days, and subsequent determination of MIC. MICs were reevaluated after 2 and 6 months of storage at -80 ° C for the isolated subpopulations with heteroresistant or induced resistance. We conducted molecular typing technique (PFGE), between the original and resistant subpopulations respective populations. Were evaluated four isolates of Klebsiella pneumoniae characterized as 4 different clones (K1, K2, K3 and K4), as well as the three isolates of Enterobacter cloacae - 2 identical clone (EC1A and Ec1b), but with different and distinct phenotypic profiles (Ec2) and a strain of Escherichia coli (E1). The initial MICs for polymyxin B, performed by broth microdilution, were between 0.0625 and 0.25 μg/mL. Four samples showed heteroresistance (K1, K2, K3 and K4), which grew at concentrations 2 (K2), 3 (K1, K4) and 6 μg/ml (K3), and their MIC after 4 days passage in antibiotic-free medium remained high (K1 4 μg/mL, K2 and K3 16 μg/mL and K4 2μg/mL). The heteroresistant subpopulations represent 0.000087% to 0.00036% of their original populations. Three samples showed adaptive resistance (K1, K3 and K4), which growth in polymyxin B concentration of 64 μg/mL and MIC after 4 days passage in antibiotic-free medium was 32 μg/ml for all three isolates. MICs remained elevated after 2 and 6 months storage, both isolates heteroresistant as those inducing resistance. By PFGE, we evaluated the clonal relationship between the initial clinical isolates and resistant subpopulations. From the 8 isolates studied, 4 isolates demonstrated heteroresistance and 3 showed adaptive resistance. The evaluation of the MIC after 2 and 6 months showed stability of subpopulations, suggesting the involvement of molecular mechanisms for both phenomena. Molecular studies should be conducted to better evaluation of heteroresistance and adaptive resistance, and understanding of clinical significance and therapeutic implications of these phenomena.

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11

Steen, Barbara R. "Identification and partial characterization of a transposon insertion mutant of Burkholderia multivorans with reduced resistance to polymyxin B." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0016/NQ48720.pdf.

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12

Jung, Philipp [Verfasser]. "Einfluß von Polymyxin B auf die biophysikalische Aktivität von exogenem Surfactant und das Wachstum von Bakterien / Philipp Jung." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2013. http://d-nb.info/1043583556/34.

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13

Medu, Erere Ohwofasa. "Examination of the antibacterial activities of some semi-synthetic chalcone-derivatives alone and in combination with polymyxin B." Thesis, Robert Gordon University, 2013. http://hdl.handle.net/10059/832.

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In view of the increasing global challenge of bacterial resistance, there exists an urgent need for the rationale development of antibacterial compounds with either novel or multiple mechanisms of action. Two chalcone-derivatives, F1 and F23, demonstrated MICs within the range of 16 to >512 μg/ml against two plant pathogens (P. caratovoram and C. michiganensis subsp. michiganensis) as well as important clinical bacterial species. Both compounds displayed an MIC of 32 μg/ml against quinolone-resistant S. aureus. Whilst possessing weak activities individually, each semi-synthetic agent displayed notable synergistic action with polymyxin B against S. aureus, C. violaceum, E. coli and Ps. aeruginosa, thereby recording FICs within the range of <0.093 to 2 that indicated the existence of synergism in some instance. These chalcone compounds applied with polymyxin B displayed a notable FICindex of <0.093 against the Neisseriaceae C. violaceum, and a potential noteworthy capacity to extend the spectrum of activity of the latter antibiotic to include Gram-positive S. aureus species. F1 inhibited staphylococcal replication in broth and the combination of either of both chalcone-derivatives with polymyxin B instituted a metabolic blockage in S. aureus and other bacterial species as determined through a modified MTT reduction assay. The combined agents inflicted major disruptions to the S. aureus cytoplasmic membrane bilayer as evidenced by the release of intracellular potassium as well as the influx of Sytox Green fluorescent stain. Notable levels of cell membrane potential dissipation, leakage of intracellular potassium ions and blockage of reducing enzymes activities occurred within the first 30 minutes, well in advance of significant loss in cell viability that was recorded usually after 4 – 8 hours, suggesting these activities were prerequisites to cell death. In erythrocyte lysis assay, the synergistic combinations of 128 μg/ml of either of both chalcone derivatives with 128 μg/ml polymyxin B displayed the lowest degree of haemolysis, followed by that occurring with 32 μg/ml of the chalcone-derivatives combined with 256 μg/ml of the polypeptide antibiotic. In conclusion, further structure activity modifications aimed at improving the aqueous solubility of these chalcone-derivatives as well as the antibacterial activity recorded for certain combination concentrations of polymyxin B with either of these semi-synthetic agents may be required before considerations are made for the possibility for potential external formulations. Such preparations may include antiseptic creams, lotions, ointments, as well as aerosols that can be applied with nebulizers in targeted delivery for such cases like cystic fibrosis.

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Kulengowski, Brandon T. "IN VITRO ACTIVITY OF POLYMYXIN B AND MEROPENEM ALONE AND IN COMBINATION AGAINST CARBAPENEM-RESISTANT ENTEROBACTERIACEAE." UKnowledge, 2016. http://uknowledge.uky.edu/pharmacy_etds/57.

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Background: Infections caused by carbapenem-resistant Enterobacteriaceae such as Escherichia coli and Klebsiella pneumoniae are among the most urgent threats of the infectious disease realm. The incidence of these infections has only been increasing over the years and due to very limited treatment options, mortality is estimated at about 50%. Methods: To evaluate the in vitro activity of meropenem and polymyxin B against carbapenem-resistant Enterobacteriaceae, antimicrobial susceptibility testing and time-kill studies were performed on K. pneumoniae clinical isolates representing a wide range of meropenem resistance (MICs 4 – 128 mg/L). Results: Regrowth was observed at clinically relevant concentrations of meropenem alone (4, 16, and 64 mg/L) or polymyxin B alone (0.25 and 1 mg/L) within 24 hours. However, meropenem and polymyxin B in combination were consistently bactericidal, achieving synergistic activity in strains with lower meropenem resistance (MICs ≤32 mg/L). Conclusions: Our findings are in agreement with the limited available literature, but we add that the synergistic interaction between meropenem and polymyxin B is dependent on the degree of meropenem resistance in KPC-producing K. pneumoniae. This data suggests that lower level resistance to carbapenems may be amenable to antimicrobial combinations involving a carbapenem and a polymyxin.

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Le, Guern Florent. "Inhibition de souches bactériennes par de nouveaux composés photosensibles conjugués à la Polymyxine B." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0075/document.

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L’émergence de nouvelles souches bactériennes résistantes a signé la fin de l’« âge d’or » des antibiotiques. L’organisation mondiale de la santé a reconnu l’imminence des problèmes associés à ces nouvelles bactéries, qui engendrent de nouveau une mortalité en augmentation. Afin de palier à ce problème, de nouvelles alternatives aux antibiotiques sont envisagées par les chercheurs à travers le monde. La thérapie photodynamique antimicrobienne est l’une de ces alternatives. Elle a su se démarquer grâce à son incapacité à induire la résistance bactérienne. Alors que les résultats furent initialement très prometteurs contre les bactéries Gram positif, une moins bonne sensibilité fut rapidement observée de la part des bactéries Gram négatif. Afin d’augmenter le potentiel antibactérien de cette technique, diverses stratégies furent élaborées comme l’utilisation de photosensibilisateurs cationiques, l’ajout d’un agent de ciblage, ou la présence d’un agent de perméabilisation membranaire. L’un de ces agents est la polymyxine B, un peptide antimicrobien qui arbore une très bonne affinité avec les bactéries Gram négatif. Dans cette étude, nous avons voulu associer chimiquement différents photosensibilisateurs avec des dérivés de polymyxines B de façon covalente, par l’intermédiaire d’un bras « spacer » ou d’une plateforme. L’association de ces deux familles de molécules a permis d’élaborer de nouveaux composés qui ont démontré une activité photobactéricide accrue contre un large spectre de bactérie. De plus, ces composés ont montré une affinité augmentée pour les bactéries, ce qui permettra de réduire les effets secondaires sur les cellules humaines. Cette étude confirme l’importance d’utiliser des peptides antimicrobiens afin d’améliorer la thérapie photodynamique. Ces travaux seront approfondis afin de permettre la création de nouveaux traitements dermatologiques basées sur cette nouvelle thérapie et efficaces contre un large spectre de souche bactérienne
Despite advances achieved over the last decade, infections caused by multi-drug resistant bacterial strains are increasingly important societal issues that need to be addressed. New approaches have already been developed in order to overcome this problem. Photodynamic antimicrobial chemotherapy (PACT) could provide an alternative to fight infectious bacteria. Interesting results have been obtained against Gram-positive bacteria, but it also appeared that Gram-negative strains were less sensitive to PACT. Enhanced efficacy against Gram-negative bacteria had been previously obtained following three differents strategies, which are respectively the use of cationic photosensitizers, photosensitizers bound to antimicrobial peptides, or a membrane disrupting agent. Polymyxin B is an antimicrobial peptide, known as the “last-line” treatment against Gram-negative resistant strains, which has already been used as a disrupting agent in order to improve PACT. In addition of this enhancement, this peptide is known for its strong interaction for Gram-negative bacteria. Thus, in this work, we designed differents coumpounds, consisting of a photosensitizer covalently attached to derivatives of polymyxin B, through a spacer or a chemical platform. These combinations have led to the creation of novel compounds which have shown highly photobactericidal activities against a wide spectrum of bacteria. Moreover, these compounds present enhanced affinity for bacteria, which should significantly reduce side effects on mammalian cells. This study confirmed the importance of using antimicrobial in order to target bacterial strains. Thus, such results may allow the creation of novels PACT-based dermatological treatments efficient against a wide spectrum of bacterial strains

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Tambadou, Fatoumata. "Étude de la production de peptides non-ribosomiques chez des souches de Paenibacillus." Thesis, La Rochelle, 2014. http://www.theses.fr/2014LAROS019/document.

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La colistine, antibiotique appartenant à la famille des polymyxines, est un polypeptide cyclique, cationique, ciblant les membranes bactériennes. Elle est produite par Paenibacillus polymyxa via des complexes multi-enzymatiques appelés Non-Ribosomal Peptides Synthétases (NRPS). Dans le cas de la mucoviscidose, et malgré des effets secondaires importants, la colistine est utilisée comme ultime recours pour lutter contre les bactéries Gram-négatives multirésistantes responsables d’infections pulmonaires dont Pseudomonas aeruginosa. Jusqu’ici les systèmes génétiques à l’origine de la production de la colistine étaient peu connus. Au cours de cette étude, nous avons caractérisé par LC-MS haute résolution des molécules antimicrobiennes, dont des colistines, produites par un nouveau Paenibacillus. Afin d’identifier et de cloner le cluster de gène responsable de la production de ces antibiotiques, une banque d’ADN génomique a été construite et criblée par homologie de séquence avec des systèmes de production déjà connus. Ce criblage a permis de sélectionner quatre clones d’intérêt. L’étude in silico de leurs séquences a permis d’identifier les différents modules d’un nouveau cluster NRPS qui serait à l’origine de la synthèse de variants de la colistine. À terme, cette découverte pourrait permettre de mieux contrôler la production de la colistine et d’obtenir des composés plus actifs et/ou présentant des effets secondaires amoindris. En parallèle à ce premier travail, nous avons également recherché la présence de nouvelles NRPS chez une centaine de micro-organismes issus d’une station d’étude environnementale du laboratoire (vasière intertidale). Ce travail a permis de découvrir des nouvelles séquences et d’isoler un nouveau micro-organisme producteur d’antibiotique(s)
Colistin is a cationic cyclic polypeptide antibiotic belonging to the polymyxin family and targeting bacterial membranes. It is produced by Paenibacillus polymyxa through a Nonribosomal Peptide Synthetase (NRPS) mechanism. In the context of cystic fibrosis (CF), colistin is used for the treatment of lung infections caused by multiresistant Gram-negative bacteria including Pseudomonas aeruginosa. Unfortunately, this molecule is also known for its strong side effects. So far, genetic systems controlling the production of polymyxins were little known. In this study we characterized by High-resolution LC-MS the antimicrobial molecules, including colistins, of a new Paenibacillus. A genomic library of this strain was constructed and screened to identify genes involved in the production of these antibiotics. A degenerated PCR screening was performed and allowed to select four clones in the genomic library. In silico study allowed to identify a new NRPS gene cluster responsible for the biosynthesis of colistin variants. In the future, this work might allow the harnessing of the production of colistin derived structures, more active and/or showing fewer side effects. In parallel, a second investigation was performed in order to find new NRPS genes in a collection of one hundred intertidal mudflat bacterial isolates. This work has allowed the identification of new sequences and the characterization of a new antimicrobial producing strain

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17

Silva, Itacy Gonçalves de Siqueira e. [UNIFESP]. "Influência dos Métodos de Sensibilidade aos Antimicrobianos no Uso Clínico das Polimixinas." Universidade Federal de São Paulo (UNIFESP), 2010. http://repositorio.unifesp.br/handle/11600/9759.

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Made available in DSpace on 2015-07-22T20:50:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-04. Added 1 bitstream(s) on 2015-08-11T03:26:26Z : No. of bitstreams: 1 Publico-304.pdf: 908273 bytes, checksum: fde22ebc553f8fa63d900f7873b29d41 (MD5)
Introdução: Acinetobacter spp. e Pseudomonas aeruginosa constituem importantes patógenos causadores de infecções relacionadas à assistência à saúde em hospitais brasileiros e tem se tornado, cada vez mais, resistentes a praticamente todos os antimicrobianos disponíveis. Dessa forma, a indicação clínica do uso parenteral das polimixinas tem sido restabelecida nos últimos anos. Consequentemente, os laboratórios de microbiologia devem estar aptos a realizar testes de sensibilidade que forneçam resultados confiáveis. Objetivo: Avaliar a influência dos métodos de sensibilidade aos antimicrobianos no uso clínico das polimixinas. Material e métodos: Foram testadas nove amostras de P. aeruginosa e 10 de Acinetobacter spp., quanto à sensibilidade à polimixina B e colistina. Foram comparados os resultados obtidos por diluição em ágar, microdiluição em caldo e Etest, realizados conforme recomendações do CLSI. Para cada metodologia foi avaliada a influência do meio de cultura, concentração de cálcio, concentração do inóculo e tempo de incubação, na determinação da CIM. Resultados: Houve uma boa correlação entre as distintas técnicas de sensibilidade às polimixinas para Acinetobacter spp., diferente de P. aeruginosa. Foi observado 100% de concordância entre os resultados obtidos com meio Iso-Sensitest e o meio Mueller-Hinton, por diluição em agar e Etest, para Acinetobacter spp. Já pela metodologia de microdiluição em caldo, essa correlação foi menor: 90% e 60% para polimixina B e colistina, respectivamente. Para P. aeruginosa, a metodologia de Etest foi a que mais sofreu variação nas CIMs, quando utilizados diferentes meios de cultura para realização dos testes de sensibilidade. Em geral, com o meio BHI foram obtidas CIMs mais baixas do que com o meio Müeller-Hinton. O aumento da concentração de cálcio no meio de cultura promoveu a elevação em ±1Log2 nas CIMs de ambas espécies, sendo a metodologia de Etest a que mais sofreu influência dessa variável, sendo que, 55,6% e 88,9% de erros leve foram observados para polimixina B e colistina, respectivamente. Além disso, 11,1% de erro grave foi observado em testes com polimixina B. A metodologia de diluição em ágar sofreu maior influencia do tamanho do inóculo do que microdiluição em caldo, apresentando taxas de erro leve de erros leve de 10% (polimixina B) e 30% (colistina), para Acinetobacter spp.; e 33,3% (polimixina B) e 66,6% (colistina), para P. aeruginosa. Quando realizada leitura com diferentes tempos de incubação, só foi observada diferenças nas CIMs entre os isolados de P. aeruginosa, sendo a metodologia de Etest a que sofreu maior influência dessa variável, onde foram observadas taxas de erro leve de 33,3% (polimixina B) e 44,4% (colistina). Pela metodologia de diluição em ágar ocorreu 11,1% de erro leve. A metodologia de microdiluição em caldo não sofreu influência dessa variável.
Introduction: Acinetobacter spp. e Pseudomonas aeruginosa are important pathogens that cause infections in Brazilian hospitals and have become resistant to almost every available antimicrobial. Thereby, the clinical indication of parenteral use of polymyxin has been reestablished in recent years. Therefore, the clinical laboratory of microbiology need be able to perform reliable susceptibility antimicrobial tests. Objective: Analyze the influence of susceptibility antimicrobial tests in the clinical use of polymyxins. Material and Methods: Nine P. aeruginosa and 10 Acinetobacter spp. strains were tested to polymyxin susceptibility. The results of agar dilution, broth microdilution and Etest were compared, according CSLI. The influence of culture medium, calcium concentration, inoculum concentration and incubation time in the susceptibility antimicrobial test was evaluated. Results: There was good agreement between different polymyxin antimicrobial susceptibility methods for Acinetobacter spp isolates, but not for P. aeruginosa. It was observed 100% of agreement between Iso-sensitest and Müeller-Hinton medium through agar dilution and Etest for Acinetobacter spp. isolates. Through broth microdilution occurred 90% of agreement for polymyxin B and 60% for colistin. Between P. aeruginosa isolates, Etest had greater MIC variation when using different culture mediuns. In general, BHI medium had low MICs comparing with Müller- Hinton. The calcium concentration increase in the culture medium promoted MICs elevation in ±1Log2 of dilution, for both microrganisms. Etest had 55,6% (polymyxin B) and 88,9% (colistin) of minor error, and 11,1% of major error in polymyxin B. Inoculum size had greater influence in agar dilution, with minor error rates of 10% (polymyxin B) and 30% (colistin) for Acinetobacter spp. isolates, and 33,3% (polymyxin B) and 66,6% (colistin) for P. aeruginosa isolates. Different time incubations caused MICs variation only between P. aeruginosa isolates. Etest method had 33,3% (polymyxin B) and 44,4%(colistin) of minor error. Through agar dilution, the minor error rate was 11,1% with incubation time variation.
TEDE
BV UNIFESP: Teses e dissertações

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Iyer, Shankar [Verfasser], and Simon [Akademischer Betreuer] Ringgaard. "Transcriptional regulation by sigma factor phosphorylation controls polymyxin resistance and swarming behavior in Vibrio parahaemolyticus / Shankar Iyer ; Betreuer: Simon Ringgaard." Marburg : Philipps-Universität Marburg, 2020. http://d-nb.info/1211086321/34.

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Iyer, Shankar Chandrashekar [Verfasser], and Simon [Akademischer Betreuer] Ringgaard. "Transcriptional regulation by sigma factor phosphorylation controls polymyxin resistance and swarming behavior in Vibrio parahaemolyticus / Shankar Iyer ; Betreuer: Simon Ringgaard." Marburg : Philipps-Universität Marburg, 2020. http://d-nb.info/1211086321/34.

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Ih, Hariyanto. "Mechanisms and PK/PD modelling of MCR-1-induced adaptive resistance in Enterobacteriaceae." Thesis, Poitiers, 2020. http://www.theses.fr/2020POIT1806.

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Du fait du manque de nouveaux antibiotiques et de l’augmentation des résistances, il est important de comprendre les mécanismes et la dynamique de ces phénomènes. La modification du lipopolysaccharide (LPS) est le principal mécanisme contribuant à la résistance des bactéries aux polymyxines. Le plasmide portant le gène MCR-1 (Mobile Colistin Resistance) retrouvé chez Escherichia coli et Klebsiella pneumoniae code une phosphoethanolamine transférase capable de modifier le LPS par une addition de phosphoethanolamine sur le lipide A du LPS alors que chez Acinetobacter baumannii résistant aux polymyxines il a été décrit à la fois des modifications du LPS par une phosphoethanolamine et une perte du LPS. Cependant, les interactions entre les différents mécanismes exprimés par ces bactéries à Gram-négatif pour devenir résistantes à la colistine et à la polymyxine B sont encore peu décrit. Les courbes de bactéricidies séquentielles ont étés utilisées comme une approche alternative pour discriminer l’héterorésistance de la population bactérienne (2 sous populations S/R) d’une résistance adaptative (AR) durant le traitement par la colistine ou la polymyxine B.Au cours de ce travail de thèse, nous avons:1. Confirmé que l’approche des courbes de bactéricidies séquentielles peut discriminer deux modèles pharmacocinétique/pharmacodynamique (PK/PD) semi-mécanistiques décrivant soit une population stable héterorésitante (S/R) soit une population bactérienne instable et homogène dont la résistance s’adapte au cours du temps (AR).2. Déterminé l’impact de la présence du plasmide MCR-1 sur les mécanismes de résistance chromosomique impliqués dans la résistance adaptative de E. coli and K. pneumoniae aux polymyxines. 3. Déterminé les mécanismes impliqués dans la résistance aux polymyxines dans deux souches cliniques d’A. baumannii, isolées avant et après traitement d’un patient à la colistine.Dans ce travail, une nouvelle approche de courbes de bactéricidies séquentielles a été utilisée et validée afin de pouvoir différencier différents modèles PK/PD semi-mécanistiques. De plus, ce travail a montré que la présence du plasmide MCR-1 favorisait l’activation d’autres mécanismes chromosomiques conduisant à de hauts niveaux de résistances aux polymyxines. Enfin, la polymyxine B montrait une plus faible capacité à induire ces mécanismes chromosomiques conduisant à de hauts niveaux de résistance
Due to the lack of new antibiotics facing the increasing emergence of resistances, it is important to understand the mechanism and dynamics of these phenomenon. Lipopolysaccharide (LPS) is the polymyxin main target and the most contributing component to polymyxin resistance. Plasmid-mediated colistin resistance MCR-1 (Mobile Colistin Resistance) carrying by Escherichia coli and Klebsiella pneumoniae encodes a phosphoethanolamine transferase leads to the addition of phosphoethanolamine to lipid A of LPS, whereas LPS modification by phosphoethanolamine and loss of LPS are the two primary mechanisms that have been described in colistin-resistant Acinetobacter baumannii to date. Polymyxin-resistance occurred during polymyxin treatment, but the mechanism and dynamics how these strains acquired resistance is poorly understood. Sequential time-kill (TK) were developed as an alternative approach to discriminate heterogenous subpopulations (S/R) versus adaptive resistance (AR) during colistin and polymyxin B exposure.In this thesis we:1. Confirm that sequential TK could discriminate between stable heterogenous subpopulation (S/R) and unstable homogenous population (AR) demonstrated by pharmacokinetics/pharmacodynamics (PK/PD) modelling.2. Determine the molecular impact of MCR-1 in the progressive adaptation of E. coli and K. pneumoniae over chromosomal genes involved to LPS modification by using the sequential TK approach. 3. Use two A. baumannii clinical isolates, a colistin-susceptible and a colistin acquired-resistant after colistin treatment, to disqualify the presence of heterogenous subpopulation or adaptive resistance. The genes involved in LPS modification and Lipid A biosynthesis were subsequently characterized after sequential TK performance.These studies not only provide a simple approach to discriminate between two PK/PD models, but also an indication that the MCR-1 presence favor another resistance mechanism leading to high-level resistance to polymyxin. By the similar approach, we determine how colistin-susceptible and resistant A. baumannii isolates respond under polymyxin pressure, including the genes involved. Furthermore, polymyxin B showed a lower capacity to induce high-level of resistance than colistin for all bacterial species

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Hermes, Djuli Milene. "Avaliação da heteroresistência à polimixina B em isolados de Pseudomonas aeruginosa." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/72433.

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Opções terapêuticas para tratar infecções por Pseudomonas aeruginosa são limitadas por seus diversos mecanismos de resistência, que podem ou não ser detectados no laboratório clínico. Um fenótipo observado na rotina laboratorial é o surgimento de subpopulações resistentes a partir de uma população sensível aos antimicrobianos – heteroresistência. Em P. aeruginosa esse fenômeno já foi investigado para carbapenêmicos, porém, em relação à polimixina B, não há dados literários. Objetivamos avaliar a heteroresistência à polimixina B em dois grupos de P. aeruginosa, um sensível e outro resistente aos carbapenêmicos. Cento e vinte e quatro isolados de P. aeruginosa foram obtidos, aleatoriamente, no Hospital de Clínicas de Porto Alegre em 2011. O perfil de susceptibilidade aos antimicrobianos, disco difusão e microdiluição em caldo – CIM (determinação da concentração inibitória mínima) para polimixina B, foi realizada conforme o Clinical Laboratory Standard Institute (CLSI) 2011. Isolados resistentes aos carbapenêmicos foram avaliados para CIM dos carbapenêmicos e cefalosporinas, e para pesquisa fenotípica e genotípica de metalo-β-lactamase (MβL). Um total de 24/124 isolados foi separado em dois grupos, um sensível (grupo S) e outro resistente (grupo R) aos carbapenêmicos (imipenem e/ou meropenem) para investigação da heteroresistência a polimixina B. Realizou-se ensaio de heteroresistência em duplicata através de diluições seriadas, partindo de uma suspensão de 0,5 de MacFarland e inoculadas em Agar Mueller Hinton com concentrações crescentes de polimixina B (0; 0,5; 1; 2; 4 e 8μg/mL). Após 5 dias de passagem em meio sem antibiótico, foi determinada a CIM dos isolados que cresceram na concentração mais alta de polimixina B. O perfil de análise populacional (PAP) foi definido pela razão do número de unidades formadoras de colônia (UFC) da placa com maior concentração de polimixina B onde houve crescimento bacteriano, pelo número de UFC da placa sem antibiótico. Foram consideradas heteroresistentes amostras que apresentaram subpopulações com crescimento em concentração de polimixina B ≥ 2 μg/mL. Amostras com subpopulações com crescimento em concentração de polimixina B superiores duas vezes ao CIM original, mas < 2 μg/mL, foram classificadas como heterogêneas. O resultado do disco difusão indicou heterogeneidade de suscetibilidade, sendo que gentamicina e imipenem foram os antibióticos com maior percentual de resistência e aztreonam e ciprofloxacino apresentaram os maiores perfis de sensibilidade. Todos os isolados foram sensíveis à polimixina B, com CIM50 e CIM90 de 1μg/mL e 2μg/mL, respectivamente. Trinta e sete isolados (30%; 37/124) apresentaram resistência aos carbapenêmicos. Quatro amostras foram positivas para MβL no teste fenotípico, sendo que o gene blaIMP foi idenficado nestas amostras. O grupo S não apresentou subpopulação heteroresistente, porém 3 isolados apresentaram subpopulação heterogênea. A freqüência do PAP no grupo S variou entre 2,1x10-4 a 4,0x10-7. O grupo R apresentou uma amostra heteroresistente e 6 isolados apresentaram subpopulação heterogênea, a freqüência do PAP variou entre 2,6x10-4 a 2,0x10-7. Os resultados deste estudo indicam baixa ocorrência de heteroresistência à polimixina B em amostras de P. aeruginosa tanto resistentes quanto sensíveis aos carbapenêmicos. No entanto, diversas amostras apresentaram subpopulações heterogêneas (CIM aumentada para a polimixina B), o que poderia explicar eventuais falhas terapêuticas durante o tratamento.
Therapeutic options to treat infections caused by Pseudomonas aeruginosa are limited because of their different resistance mechanisms that can be or don't be detected in the clinical laboratory. A phenotype that has been observed in our laboratory is the emergence of resistant subpopulations from a population sensitive to antibiotics - a phenomenon named heteroresistance. In P. aeruginosa this phenomenon has been investigated for carbapenems, however, in relation to the polymyxin B no data in the literature. We investigate the heteroresistance and polymyxin B into two groups P. aeruginosa, one sensitive and second resistant to carbapenems. One hundred twenty-four strains of P. aeruginosa were obtained randomly at the Hospital de Clinicas de Porto Alegre in 2011. The Antimicrobial Susceptibility Testing (Disk-difusion and the microdiluition broth, with determination of minimum inhibitory concentration (MIC) for polymyxin B, was performed according the Clinical Laboratory Standards Institute (CLSI), 2011. Isolates resistant to carbapenems were evaluated for MIC of carbapenems and cephalosporins, also for phenotypic and genotypic metallo-β-lactamase (MβL). A total of 24/124 strains were separated in two groups, one sensitive (S group) and other resistant (R group) to carbapenems (imipenem and / or meropenem) for investigation of heteroresistance polymyxin B. The assay was performed in duplicate heteroresistance through serial dilutions, starting from a 0.5 MacFarland suspension and inoculated into Mueller Hinton Agar with increasing concentrations of polymyxin B (0; 0,5; 1; 2; 4 e 8μg/mL). After 5 days of passage in medium without antibiotics, was determined the MIC of the isolates that grew at the highest concentration of polymyxin B. The population analysis profile (PAP) was defined as the ratio of the number of colony forming units (CFU) on the card with the highest concentration of polymyxin B in which bacterial growth, the number of CFU plate without antibiotic. We considered heteroresistant samples that showed subpopulations with growth in concentration of polymyxin B ≥ 2 mg / mL. Samples with subpopulations growing at higher concentration of polymyxin B twice CIM original, but <2 mg / mL were classified as heterogeneous. The result of AST indicated heterogeneity of susceptibility, and gentamicin and imipenem were the highest percentage with antibiotic resistance and aztreonam and norfloxacin showed the highest sensitivity profiles. All isolates were susceptible to polymyxin B, with CIM50 and CIM90 of 1μg/mL and 2μg/mL, respectively. Thirty-seven isolates (30%; 37/124) were resistant to carbapenems. Four samples were positive for the phenotypic test to MβL and the blaIMP gene was indentificated in this samples. The S group showed no subpopulation heteroresistente, but 3 isolates showed heterogeneous subpopulation. The frequency of PAP in group S varied between 2,0x10-4 to 4,0x10-7. The group R provided a sample heteroresistant and 6 isolates showed heterogeneous subpopulation, the frequency of PAP varied between 2,6x10- 4 a 2,0x10-7. The results of this study indicate a low occurrence of heteroresistance to polymyxin B in samples of P. aeruginosa so resistant assensitive to carbapenems. However, several samples showed heterogeneous subpopulations (MIC increased to polymyxin B) which could explain possible treatment failure during treatment.

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Rigatto, Maria Helena da Silva Pitombeira. "Nefrotoxicidade de polimixinas : fatores de risco e comparação entre polimixina B e colistina." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/119424.

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Base teórica: As polimixinas, polimixina B e polimixina E (também denominada colistina), são antibióticos usados como opção de última linha no tratamento de infecções por bacilos Gram negativos multirresistentes. Apesar de serem drogas antigas, suas propriedades nefrotóxicas ainda são pobremente entendidas. Toxicidade direta aos túbulos renais proximais levando à necrose tubular e dano oxidativo estão envolvidos no mecanismo fisiopatológico da nefrotoxicidade por esta classe de drogas. Uso de maior dose total foi implicada em maior nefrotoxicidade, no entanto a relação entre dose recebida e peso do paciente, controlado para outras variáveis confundidoras ainda precisa ser clarificada. Além disso, diferenças farmacocinéticas entre polimixina B e a colistina impedem o extrapolamento de dados entre estas drogas, sendo importante a avaliação de desfecho clínico e nefrotoxicidade de cada uma e a comparação entre elas. Objetivo: Avaliar comparativamente a nefrotoxicidade (através de critério de RIFLE) e mortalidade em 30 dias em pacientes tratados com polimixina B e colistina. Métodos: Estudo de coorte prospectivo, multicêntrico com coleta consecutiva de dados. Critérios de inclusão: pacientes ≥ 18 anos em uso de polimixina B ou colistina. Critérios de exclusão: uso de polimixina B por período ≤48 horas, segundo uso de polimixina B, diálise no início do tratamento ou DCE ≤ 10ml/min nos pacientes avaliados para nefrotoxicidade. Fatores potencialmente relacionados à nefrotoxicidade ou a mortalidade em 30 dias como: variáveis demográficas (idade, sexo), variáveis individuais (peso, comorbidades, escore de Charlson), fatores de gravidade (escore APACHE, internação em UTI, ventilação mecânica, uso de vasopressor), fatores relacionados à nefrotoxicidade (outras drogas nefrotóxicas e uso de contraste endovenoso), dose de polimixina utilizada (total, média diária e em mg/kg/dia), associação de drogas e características da infecção ( sítio e isolado microbiológico) foram avaliadas em análise bivariada. Variáveis com P≤0.2 foram incluídas uma a uma, em ordem crescente, em modelo de regressão de COX. Variáveis com P< 0.1 permaneceram no modelo final. Resultados: Quatrocentos e dez pacientes foram incluídos na coorte de polimixina B. Nefrotoxicidade ocorreu em 189 (46.1%) pacientes. Dose de polimixina B ≥150mg/dia foi fator de risco independente para nefrotoxicidade: adjusted Hazard Ratio (HR) 1.95, IC 95% 1.31-2.89, P=0,01. Peso e idade também foram associados de forma independente com nefrotoxicidade. A probabilidade de desenvolver nefrotoxicidade aumentou significativamente com doses entre 150-199mg/dia, independente do peso do pacientes, sem aumento significativo com doses maiores. Nefrotoxidade foi relacionada à maior mortalidade em 30 dias, embora não tenha atingido significância estatística (aHR 1,35, IC 95% 0,99-1,85, P=0,06), enquanto dose ≥150mg/dia não aumentou o risco de mortalidade apesar de sua associação com nefrotoxicidade. Na avaliação de mortalidade foram avaliados apenas pacientes internados em UTI e com infecção microbiologicamente confirmada. Cento e nove pacientes foram incluídos: 47 (43.1%) tratados com polimixina B combinada com outro antibiótico e 62 (56.8%) com polimixina B em monoterapia. A mortalidade geral em 30 dias foi 56.9% (62 pacientes): 32,3% (20 de 47) e 67,7% (42 de 62), P=0,02, nos grupos de terapia combinada e monoterapia, respectivamente. Terapia combinada foi associada de forma independente à menor mortalidade em 30 dias (HR, 0,38; IC 95% 0,21-0,68; P=0,001). Maior escore APACHE foi fator de risco independente para mortalidade em 30 dias. Oitenta e um pacientes foram incluídos na coorte de colistina e foram pareados com 162 pacientes do grupo de polymyxin B, de acordo com a DCE (±25ml/min). A incidência falência renal foi de 23,5%: 38.3% no grupo da colistina e 16.1% no grupo da polimixina B, P<0,001 e ocorreu independente da DCE de base. Na análise multivariada, terapia com colistina foi fator de risco independente para falência renal (HR, 2,96, IC95%, 1,68- 5,22, P<0,001), assim como internação em UTI, maior peso e idade . Pacientes que desenvolveram falência renal morreram mais (50,9%, 29/57) do que os que não a desenvolveram (29.0%, 54/186), P=0,004; mas a mortalidade em 30 dias não diferiu entre os grupos: 30.9% e 35.8%, P=0,53, nos pacientes em uso de colistina e polimixina B, respectivamente. Conclusão: A dose média diária de polimixina B é diretamente relacionada ao risco de nefrotoxicidade, independente do peso do paciente. Mortalidade em 30 dias tendeu a ser maior em quem desenvolveu nefrotoxicidade. O uso de terapia combinada com polimixina B mostrou ser protetor para mortalidade em 30 dias. Colistina mostrou estar associada ao maior desenvolvimento de falência renal quando comparada à polimixina B.
Background: Polymyxins, polymyxin B and polymyxin E (also called colistin), are last line resort therapies to treat multi-resistant Gram negative bacteria. Despite the fact that they are old antibiotics, their nephrotoxicity properties are still poorly understood. Direct proximal renal tubular toxicity leading to tubular necrosis and oxidative damage are involved in the physiopathologic mechanism of injury by these drugs. Higher doses were implicated in nephrotoxicity, however the relation between dose and weight, controlled for confounding variables, still need to be clarified. Moreover, pharmacokinetic diferences between polymyxin B and colistin avoid direct extrapolation of data between these drugs. It is then important to evaluate clinical outcomes and nephrotoxicity of each of these drugs and to compare its results. Objective: To compare nephrotoxicity (using RIFLE score) and 30-day mortality in patients treated with colistin and polymyxin B. Methods: We performed a multicenter prospective cohort study with consecutive data collection. Inclusion criteria: patients ≥ 18 years old receiving polymyxin B or colistin. Exclusion criteria: polymyxin use for ≤48 hours, having received polymyxin before, dyalisis or GFR≤ 10ml/min in the beginning of therapy in patients evaluated for nephrotoxicity. Factors potentially related to nephrotoxicity or 30-day mortality such as: demographic data (age, gender), individual characteristics (weight, comorbidities, Charlson score), disease severity factors (APACHE score, ICU admission, mechanical ventilation, use of vasoactive drugs, nephrotoxicity related factors ( other nephrotoxic drugs and use of nephrotoxic contrast), polymyxin dose (total dose, average daily dose, mg/kg/day dose), combined therapy and infection characteristics (site of infection, microbiologic isolates) were evaluated in bivariate analysis. Variables with P≤0.2 were included one by one, in a COX regression model. Variables with P< 0.1 remained in the final model. Results: Four-hundred and ten patients were included. AKI occurred in 189 (46.1%) patients. Polymyxin B dose ≥150mg/day was a risk factor for AKI: adjusted Hazard Ratio (HR) 1.95, 95% CI 1.31-2.89, P=0.01. Higher weight and age were also independently associated with AKI. The probability of developing AKI significantly increases with doses between 150-199mg/day, regardless the patients’ weight, with no significant increase with higher doses. AKI was barely associated with increased risk for 30-day mortality (adjusted HR 1.35, 95% CI 0.99-1.85, P=0.06), while ≥150mg/day did not increase this risk despite its association with AKI. On mortality evaluation, a total of 109 patients were included: 47 (43.1%) treated with polymyxin B in combination and 62 (56.8%) with polymyxin B in monotherapy. The overall 30-day mortality was 56.9% (62 patients): 32.3% (20 of 47) and 67.7% (42 of 62), p=0.02, in combination and monotherapy groups, respectively. Combination therapy was independently associated with lower 30-day mortality (Hazard Ratio, 0.38; 95%CI 0.21-0.68; p=0.001), along with a higher APACHE score. Eighty one patients in colistin group were matched to 162 in polymyxin B group, according to baseline creatinine clearance (±25ml/min). . The incidence of renal failure was 23.5%: 38.3% in CMS and 16.1% in polymyxin B group, P<0.001, regardless the baseline creatinine clearance of patients. In multivariate analysis, CMS therapy was an independent risk factor for renal failure (Hazard Ration, 2.96, 95%Confidence Interval, 1.68-5.22, P<0.001), along with intensive care unit admission, higher weight and older age. Patients who developed renal failure presented higher 30-mortality rates (50.9%, 29/57 patients) than those who did not present renal failure (29.0%, 54/186), P=0.004; but CMS (30.9%) and polymyxin B (35.8%) treated patients had similar 30-day mortality, P=0.53. Conclusion: Median daily dose of polymyxin B therapy was directly related to the risk of developing nephrotoxicity, regardless of patient’s weight. 30-day mortality was higher in patients who developed nephrotoxicity. Combined therapy with polymyxin B was protective to 30-day mortality. Colistin use was related to higher rates of renal failure when compared to polymyxin B.

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Alves, Paola Hoff. "Atividade da polimixina B isoladamente e em combinação com tigeciclina, meropenem e ertapenem frente a isolados de Enterobacter sp. resistentes aos carbapenêmicos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/156633.

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Diante do aumento global da resistência microbiana, cada vez mais as combinações de antimicrobianos são utilizadas na tentativa de obter uma atividade sinérgica eficaz que possa ser utilizada na prática clínica. O objetivo deste trabalho foi comparar a atividade de polimixina B isoladamente e em combinação com tigeciclina e carbapenêmicos (ertapenem e meropenem), frente a isolados de Enterobacter sp. resistentes aos carbapenêmicos. Foram selecionados quatro isolados de Enterobacter sp. resistentes aos carbapenêmicos, sendo três isolados produtores de carbapenemases (KPC, NDM, OXA-48-like) e um não produtor de carbapenemases (NPC). A avaliação da atividade sinérgica antimicrobiana foi realizada por ensaio de time-kill com as seguintes concentrações de cada antimicrobiano: tigeciclina 1mg/L, meropenem 1mg/L e ertapenem 0,5mg/L, que correspondem aos pontos de corte de sensibilidade do CLSI (2016). Para polimixina B, foram utilizadas diferentes concentrações de acordo com o perfil de susceptibilidade do isolado: para os isolados sensíveis, utilizou-se 0,5x; 1x e 2x a CIM do isolado; para o isolado resistente, foram utilizados 0,5x; 1x e 2x o ponto de corte de sensibilidade do CLSI (2 mg/L). Foi considerada sinérgica a combinação com redução ≥ 2 logs do inoculo inicial em comparação ao antimicrobiano sozinho mais ativo. As combinações de polimixina B em diferentes concentrações (0,5; 1 e 2mg/L) com meropenem apresentaram atividade sinérgica para a cepa produtora de NDM (CIM polimixina B 1 mg/L; CIM meropenem 8 mg/L) As combinações de polimixina B com tigeciclina foram sinérgicas apenas na concentração de polimixina B de 0,125 mg/L para cepa produtora de OXA-48-like (CIM polimixina B 0,25 mg/L; CIM tigeciclina 2 mg/L) e na concentração de 1 mg/L para a cepa produtora de NDM. Para a cepa NPC (CIM polimixina B 0,5 mg/L; CIM tigeciclina 4 mg/L; CIM meropenem 4 mg/L), apenas a tripla combinação com polimixina B (1 mg/L), tigeciclina e meropenem apresentou atividade sinérgica. A combinação de dois carbapenêmicos não apresentou atividade sinérgica para nenhum isolado, porém, quando acrescentado tigeciclina ao esquema, observou-se sinergismo no isolado produtor de OXA-48-like, o que leva ao questionamento da efetividade da terapia “carbapenem suicida”. Para o isolado produtor de KPC e com padrão de resistência a polimixina B, nenhuma das combinações testadas apresentou sinergismo. Esta situação é bastante preocupante devido à alta prevalência de infecções por bactérias produtoras de KPC nos hospitais brasileiros, juntamente com as crescentes taxas de resistência as polimixinas.
Due to the increase in microbial resistance, combinations of antimicrobials are increasingly being used to improve the therapeutic response. The objective of this study was to compare the activity of polymyxin B alone and in combination with tigecycline and carbapenem (ertapenem and meropenem) against to carbapenem-resistant Enterobacter sp isolates. Four isolates were selected, three were carbapenemase-producing (KPC, NDM, OXA-48-like) and a non-carbapenemase-producing (NCP). The evaluation of synergistic antimicrobial activity was performed by time-kill assay with the following concentrations of each antimicrobial: tigecycline 1mg/L, meropenem 1mg/L and ertapenem 0.5mg/L, which correspond to the breakpoints of CLSI (2016). For polymyxin B, different concentrations were used according to the susceptibility profile of the isolate: for susceptible isolates, it was used 0.5x; 1x and 2x the MIC of the isolate, for the resistant isolates it was used 0.5x; 1x and 2x the breakpoint of CLSI (2 mg/L). The combination with reduction ≥ 2 logs of the initial inoculum compared to the most active antimicrobial alone was considered synergies. Combinations of polymyxin B at different concentrations (0.5; 1 and 2 mg/L) with meropenem showed synergistic activity for the NDM-producing isolate (MIC polymyxin B 1 mg/L, MIC meropenem 8 mg/L) Combinations of polymyxin B with tigecycline were synergistic only at the concentration of polymyxin B of 0.125 mg/L for the OXA-48-like-producing isolate (MIC polymyxin B 0.25 mg/L, MIC tigecycline 2 mg/L) and at the concentration of 1 mg/L for the NDM-producing isolate. For the NCP isolate (MIC polymyxin B 0.5 mg/L; MIC tigecycline 4 mg/L; MIC meropenem 4 mg/L), only the triple combination of polymyxin B (1 mg/L) plus tigecycline and meropenem presented synergistic activity. The combination of two carbapenems was not synergic for the four isolates; however, when tigecycline was added to the regimen, synergies for the OXA-48-like-producing isolate were observed. Therefore, the so called, "carbapenem suicide" therapy was not effective in vitro against our isolates. For the KPC-producing isolate that it is polymyxin B resistant, none of the combinations tested showed synergies. This situation is very worrisome due to high prevalence of infections by KPC-producing in the Brazilian hospitals, associate with the increasing rates of polymyxins resistance.

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Jayol, Aurélie. "Résistance à la colistine chez les bacilles Gram négatif." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0179/document.

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Les entérobactéries productrices de carbapénèmases peuvent être responsables d’impasses thérapeutiques puisque ces souches sont multirésistantes aux antibiotiques. La colistine, un antibiotique de la famille des polymyxines, fait partie des molécules de derniers recours potentiellement utilisables pour le traitement des patients infectés par ces souches. Son utilisation est ainsi en augmentation constante mais des résistances émergent.Ce travail a contribué à l’amélioration du diagnostic de la résistance à la colistine par le développement de deux nouveaux outils diagnostiques : un test rapide, le Rapid Polymyxin NP test et un milieu de culture sélectif, la gélose SuperPolymyxin. Il a permis d’identifier de nouvelles mutations chromosomiques au sein des gènes pmrA, pmrB, phoP, phoQ, mgrB et crrB responsables de l’acquisition de résistances et d’hétérorésistance à la colistine chez K. pneumoniae et K. oxytoca. Il a révélé que les mutations chromosomiques et les résistances plasmidiques étaient additionnelles et pouvaient entraîner l’acquisition d’un haut niveau de résistance à la colistine chez E. coli. Il a permis d’identifier une épidémie de souches de K. pneumoniae productrices de la carbapénèmase OXA-48 et résistantes à la colistine en France en 2014. Il a démontré que Hafnia était un genre d’entérobactéries présentant une résistance naturelle de bas niveau à la colistine. Enfin, il a permis de proposer une option thérapeutique, le ceftazidime/avibactam en association ou non avec l’aztréonam, pour traiter les patients infectés par les souches de K. pneumoniae productrices de carbapénèmases et résistantes à la colistine.Ce travail a ainsi contribué à améliorer les connaissances sur la résistance à la colistine chez les BGN au niveau du diagnostic, des mécanismes de résistance acquis, des résistances naturelles, et de l’épidémiologie et a permis de proposer des combinaisons d’antibiotiques actives in vitro sur les souches de K. pneumoniae productrices de carbapénèmases et résistantes à la colistine
Carbapenemase-producing Enterobacteriaceae may be responsible for therapeutic impasses since these strains are multidrug-resistant. Colistin, an antibiotic of the polymyxin family, is one of the last-resort molecules potentially usable for the treatment of patients infected with these strains. Its use is thus constantly increasing but resistances emerge.This work contributed to improve the diagnosis of colistin resistance by developing two new diagnostic tools: a rapid test, the Rapid Polymyxin NP test and a selective culture medium, the SuperPolymyxin agar. It identified new chromosomal mutations within the pmrA, pmrB, phoP, phoQ, mgrB and crrB genes responsible for the acquisition of colistin resistance and heteroresistance in K. pneumoniae and K. oxytoca. It revealed that chromosomal mutations and plasmid resistance were additional and could lead to the acquisition of a high level of colistin resistance in E. coli. It identified an outbreak caused by colistin-resistant OXA-48-producing K. pneumoniae strains in France in 2014. It demonstrated that Hafnia was a genus of enterobacteria with low-level intrinsic resistance to colistin. Finally, it suggested a therapeutic option, the ceftazidime / avibactam in combination or not with aztreonam, to treat patients infected with colistin-resistant and carbapenemase-producing K. pneumoniae.This work has significantly contributed to improve the knowledge of colistin resistance in Gram negatives in diagnostic, in characterization of acquired or intrinsic resistance mechanisms, and in epidemiology

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Rodríguez, Falcón Manuel. "Proteómica de expresión diferencial en Acinetobacter baumanii resistente a colistina." Doctoral thesis, Universitat Pompeu Fabra, 2010. http://hdl.handle.net/10803/31820.

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Normally present in water, soil and waste water, Acinetobacter baumannii has become an important nosocomial pathogen, as causal agent of pneumonias, septicemias and urinary tract infections, among other complications in compromised patients from hospital’s intensive care units. One of its last acquired abilities is the resistance to colistin (polymixin E), the last therapeutic option for its infections. In this thesis, descriptive and quantitative differential expression proteomics is used in the study of acquired colistin resistance. As result of this research, 1,097 proteins belonging to the Acinetobacter genus have been identified by combined application of bidimensional gel electrophoresis (2DE), differential gel electrophoresis (DIGE), and peptide labeling with stable isobaric isotopes tags (iTRAQ). Analyses have been performed on the global expressed proteome of a reference, colistin-sensible strain (A. baumannii ATCC 19606) and, for comparative purposes, on a derived strain on which colistin resistance has been induced in vitro. The resistant phenotype shows reduced fitness, with significant differences in expression found in outer membrane proteins, membrane active transporters, diverse metabolic enzymes (fatty acids, citrate, phenylacetate, piruvate and nitrogen), proteins involved in stress response and biofilm formation, as well as in protein synthesis and folding pathways. The work has allowed to assess the strengths and weaknesses of the different techniques currently used in this type of proteomic analysis.
Acinetobacter baumannii, normalmente aislado en suelos y aguas (corrientes o residuales), se ha convertido en importante patógeno nosocomial, siendo agente causal de, entre otras complicaciones, neumonías, septicemias e infecciones del tracto urinario de pacientes comprometidos en unidades hospitalarias de cuidados intensivos. La más reciente de sus capacidades adquiridas es la resistencia a colistina (polimixina E), antibiótico peptídico considerado la última opción terapéutica en contextos clínicos. Esta tesis doctoral emplea la proteómica descriptiva y de expresión diferencial cuantitativa para investigar la resistencia adquirida por A. baumannii a dicho antibiótico. Los resultados han supuesto la identificación de 1.097 proteínas de Acinetobacter mediante el empleo combinado de electroforesis bidimensional convencional (2DE), 2DE diferencial (DIGE) y marcaje peptídico mediante isótopos isobáricos estables (iTRAQ). Los análisis se han realizado en el proteoma expresado por una cepa de referencia sensible a colistina (A. baumannii ATCC 19606), así como en una cepa derivada de ésta en la que se ha inducido, a efectos comparativos, resistencia a colistina in vitro. El fenotipo resistente manifestó reducida adaptabilidad biológica, encontrándose las principales diferencias en la estructura de la membrana externa, en la expresión de transportadores activos de membrana, en diversos enzimas metabólicos (ácidos grasos, citrato, fenilacetato, piruvato, nitrógeno) y de respuesta a condiciones de estrés, así como en la expresión de proteínas participantes en la formación de biopelículas y en el proceso de síntesis y plegamiento de proteínas. Además, el trabajo ha permitido evaluar los puntos fuertes y débiles de las técnicas empleadas actualmente en este tipo de análisis proteómicos.

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Pacheco, Liliane Souto. "AVALIAÇÃO DOS DESFECHOS CLÍNICOS COM USO DA TERAPIA ANTIMICROBIANA: POLIMIXINA B." Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/5842.

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This study aims at evaluating the clinical outcomes with the use of Polymyxin B, antibiotic that is being increasingly used across the current needs of antimicrobial therapy. Was developed in the 40s for the treatment of gram-negative bacilli, and fell into disuse because of its toxicity, mainly renal. Despite this increased use is poorly understood its true efficacy and its toxicity profile (ZAVASCKI et al., 2010, p.71). Among the clinical outcomes analyzed the mortality at 30 days and the occurrence of acute kidney injury (AKI). This evaluation was made by means of a retrospective cohort study, based on data collection from medical records of adult patients admitted to the University Hospital of Santa Maria (HUSM), who received Polymyxin B for more than 48 hours. For evaluation of the nephrotoxicity RIFLE criteria were used. The diagnosis of infection was made according to the criteria of the National Health Surveillance Agency (Anvisa). We evaluated 53 patients, mean age 56 years, 29 (55%) men and 24 (45%) women. AKI occurred in 25 (53%) participants, with an average start of 8.5 (± 4.9) days. In thirty days, 12 (48%) patients showed improvement of renal function to pretreatment levels. Doses above 25 mg / kg / day and previous normal renal function, doses were positively correlated with worsening kidney. Regarding the clinical outcome observed that 29 (55%) had a favorable outcome at 14 days. Eighteen (34%) participants died within 30 days after initiation of treatment. As risk factors for death were found combined use with other active drug to BGN resistant to carbapenems (p-value 0.028, RR 13 CI 1.3 to 130), and SOFA score greater than eight (p-value <0.029, RR 1.3 CI 15 to 179). The conclusion is based on these findings, the mortality related to use of Polymyxin B is dependent on the degree of comorbidities presented by the patient (SOFA) and the use or not of combination therapy. This last finding may be due to a bias of severity of infection. When it was found that nephrotoxicity is an agent with nephrotoxic potential, and that the occurrence of AKI is influenced by the prescribed daily dosage. The fact of the LRA have been more frequent in patients without renal injury corroborates the hypothesis that greater care with other causative factors for AKI may decrease its occurrence in patients using polymyxin B.
Este estudo tem como objetivo a avaliação dos desfechos clínicos com a utilização da Polimixina B, antibiótico que vem sendo cada vez mais utilizado frente às necessidades atuais de terapia antimicrobiana. Foi desenvolvido na década de 40 para o tratamento de bacilos gram-negativos (BGN) e, entrou em desuso devido a sua toxicidade, principalmente renal. Apesar deste crescente uso permanece pouco entendidos a sua real eficácia e seu perfil de toxicidade (ZAVASCKI et al., 2010, p.71). Dentre os desfechos clínicos analisados incluíram-se a mortalidade em 30 dias e a ocorrência de lesão renal aguda (LRA). Essa avaliação foi feita por meio de uma coorte retrospectiva, baseada na coleta de dados do prontuário médico de pacientes adultos, internados no Hospital Universitário de Santa Maria (HUSM), que receberam Polimixina B por mais de 48 horas. Para avaliação da nefrotoxicidade foram utilizados os critérios Risk Injury Failure Loss Endstage renal disease(RIFLE). O diagnóstico das infecções foi feito conforme os critérios da Agência Nacional de Vigilância Sanitária (ANVISA). Foram avaliados 53 pacientes, com idade média de 56 anos, sendo 29 (55%) homens. Ocorreu LRA em 25 (47%) participantes, com média de início de 8,5 (±4,9) dias. Em trinta dias, 12 (48%) dos pacientes apresentaram melhora da função renal a níveis pré-tratamento. Doses superiores a 25 mg/Kg/dia e função renal prévia normal, tiveram correlação positiva com a piora renal. Quanto ao desfecho clínico observamos que 29 (55%) tiveram um desfecho favorável em 14 dias. Dezoito (34%) participantes faleceram em 30 dias após o início do tratamento. Como fatores de risco para o óbito foram encontrados o uso combinado com outra droga ativa para BGN resistente à carbapenêmicos (p-valor 0,028, RR 13 IC 1,3-130), e escore SOFA superior a oito (p-value <0.029, RR 15 CI 1,3 to 179). Conclui-se com base nesses achados, que a mortalidade relacionada com uso da Polimixina B é dependente do grau de co-morbidades apresentado pelo paciente (escore SOFA) e do uso ou não de terapia combinada. Podendo esse ultimo achado dever-se a um viés de gravidade da infecção. Quando a nefrotoxicidade encontrou-se que é um agente com potencial nefrotóxico, e que a ocorrência da LRA é influenciada pela dose diária prescrita. O fato da LRA ter sido mais frequente em pacientes sem lesão renal prévia corrobora com a hipótese de que um maior cuidado com outros fatores causadores de LRA pode diminuir sua ocorrência em pacientes que utilizam Polimixina B.

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Netto, Bárbara Helena Teixeira. "Avaliação de sinergismo de polimixina B com outros antimicrobianos em isolados de Acinetobacter baumannii resistentes aos carbapenêmicos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/72118.

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A.baumannii é um importante patógeno em infecções nosocomiais principalmente por sua capacidade de se tornar resistente aos antimicrobianos. Surtos de A.baumannii resistente aos carbapenêmicos (ABRC) têm sido descritos em todo mundo. Devido à emergência de resistência aos antimicrobianos e ausência de novas opções de tratamento, as polimixinas reemergiram como opção de terapia contra infecções causadas por A.baumannii. O uso de polimixina é associado a maior mortalidade e menor eficácia comparada a outros antimicrobianos. Alguns estudos in vitro têm avaliado a combinação de polimixina com outros antimicrobianos a fim de aumentar a eficácia dos tratamentos. O objetivo deste estudo foi avaliar o sinergismo entre a polimixina B com outros antimicrobianos em isolados de ABRC, pelo método de Curvas Tempo-Morte bacteriana (Time- Kill Curves). Os isolados foram provenientes de banco de amostras e foram avaliadas as combinações de polimixina B com carbapenêmicos (imipenem e meropenem), tigeciclina, rifampicina, amicacina e ceftazidima. As combinações foram testadas nos tempo 0, 30’, 1,4,12 e 24 h. Sinergismo entre polimixina B foi demonstrado contra todos antimicrobianos para ambos isolados, exceto para ceftazidima e imipenem no isolado 1. Nosso estudo mostrou que tigeciclina, amicacina e rifampicina são agentes mais ativos combinados com polimixina B, sendo assim estes agentes podem apresentar efeito benéfico em combinação com a polimixina no tratamento de ABRC.
A.baumannii is an important pathogen in nosocomial infections primarily for its ability to become resistant to antimicrobials. Outbreaks carbapenem- resistant A.baumannii (CRAB) has been described worldwide. Due to the emergence of antimicrobial resistance and the absence of new treatment options, the polymyxins reemerged as an option therapy against infections caused by A.baumannii. The use of polymyxin is associated with higher mortality and lower effectiveness compared to other antimicrobials. In vitro studies have evaluated the combination of polymyxin with other antimicrobial agents to enhance the effectiveness of the treatments. This study was to evaluate the synergy between polymyxin B with other antimicrobials in isolates from ABRC, by Time-Kill Curves. The isolates were from stool samples and were evaluated combinations of polymyxin B with carbapenems (imipenem and meropenem), tigecycline, rifampin, amikacin and ceftazidime. The combinations were tested at time 0, 30 ', 1,4,12 and 24 h. Synergism between polymyxin B was demonstrated against all antimicrobials for both isolates, except for ceftazidime and imipenem in isolated 2. Our study showed that tigecycline, amikacin and rifampicin more active agents are combined with polymyxin B, and thus these agents may have a beneficial effect in combination with a polymyxin in treating CRAB.

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Wilhelm, Camila Mörschbächer. "Avaliação da atividade de amicacina e polimixina B isoladamente e combinados com imipenem frente a isolados de P. aeruginosa resistentes a carbapenêmico." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/157913.

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Base teórica: Devido à diminuição do desenvolvimento de novos antimicrobianos nas últimas décadas, terapias combinadas têm sido empregadas contra bactérias multirresistentes como opção à monoterapia no tratamento de infecções graves. Para tratar infecções causadas por Peusdomonas aeruginosa resistente a carbapenêmicos, amicacina e polimixina B têm sido utilizadas em associações com imipenem, pois possuem diferentes mecanismos de ação, o que, teoricamente, indicaria a possibilidade de efeito sinérgico. Objetivo: O objetivo deste trabalho foi verificar a interação, in vitro, de amicacina e polimixina B em associação com imipenem frente a diferentes isolados de P. aeruginosa resistentes a carbapenêmico. Métodos: Foram selecionados isolados de P. aeruginosa resistentes a carbapenêmico oriundos do Hospital de Clínicas de Porto Alegre, coletados no período de janeiro a março de 2015. Foi realizada eletroforese em gel de campo pulsado e detecção do gene blaSPM-1 para selecionar diferentes clones. Seis isolados (três SPM-1 positivos e três negativos para a carbapenemase) foram selecionados para realização da técnica de time-kill, a fim de avaliar a atividade antimicrobiana das combinações de imipenem com amicacina e imipenem com polimixina B. Resultados: Sinergismo ocorreu para combinações de imipenem com amicacina em 3 isolados, dos quais um era SPM-1 positivo e dois eram SPM-1 negativos e todos apresentaram CIMs relativamente baixas a intermediárias. Quanto às combinações de imipenem com polimixina B, houve sinergismo somente para dois isolados, um SPM-1 positivo e um SPM-1 negativo, contudo houve antagonismo em 5 isolados, dois SPM-1 positivos e três SPM-1 negativos. Para 4 isolados, as combinações de imipenem com amicacina tiveram atividade bactericida, enquanto, para todos os isolados, as combinações de imipenem com polimixina B, bem como polimixina B isoladamente, 1x e 2x a CIM apresentaram atividade bactericida. Conclusão: Sinergismo pode ocorrer, para combinações de imipenem mais amicacina, quando os isolados apresentam CIMs relativamente baixas ou intermediárias para imipenem (≤16 μg/mL a 128 μg/mL) e amicacina (≤32 μg/mL). Entretanto, antagonismo aconteceu independentemente de valores altos ou baixos de concentrações inibitórias mínimas para imipenem e polimixina B. Além disso, a presença ou ausência do gene blaSPM-1 não pareceu influenciar nos resultados.
Background: Due to a decrease on new antibiotic development over the last decades, combined therapies have been employed against multigrug-resistant bacteria as an option to monotherapy in severe infection treatment. In order to treat infections caused by carbapenem resistant Pseudomonas aeruginosa, amikacin and polymyxin B have been used in associations with imipenem, because they possess different mechanisms of action, which could, theoretically, indicate the possibility of synergistic effect. Objective: The aim of this study was to verify the interaction, in vitro, of amikacin and polymyxin B in association with imipenem against various carbapenem resistant P. aeruginosa isolates. Methods: Carbapenem resistant P. aeruginosa isolates have been selected from Hospital de Clínicas de Porto Alegre, collected from January to March 2015. Pulsed field gel electrophoresis and detection of blaSPM-1 gene has been performed to select different clones. Six isolates (three SPM-1 positive and three negative for the carbapenemase) were selected for time-kill assay, in order to assess antimicrobial activity of imipenem plus amikacin and imipenem plus polymyxin B combinations. Results: Synergism occurred for combinations of imipenem plus amikacin in three isolates, from which one was SPM-1 positive and two were SPM-1 negative, and all presented relatively low to intermediate minimum inhibitory concentrations. About imipenem plus polymyxin B combinations, synergism occurred in only two isolates, one SPM-1 positive and one SPM-1 negative, however antagonism occurred in five isolates, two SPM-1 positive and three SPM-1 negative. For 4 isolates, imipenem plus amikacin combinations had bactericidal effect, while, for all isolates, combinations of imipenem plus 1x and 2x the MIC of polymyxin B presented bactericidal activity. Conclusions: Synergism can occur, for imipenem plus amikacin combinations, when isolates present relatively low or intermediate MIC of imipenem (≤16 μg/mL to 128 μg/mL) and amikacin (≤32 μg/mL). However, antagonism happened regardless high or low minimum inhibitory concentrations for imipenem and polymyxin B. Also, the presence or absence of blaSPM-1 gene did not seem to influence the results.

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Vecchi, Rafael. "Avaliação do perfil de sensibilidade de Klebsiella pneumoniae resistente aos carbapenêmicos e à polimixina B frente a polimixina B modificada pela complexação ao íon metálico cobre." Botucatu, 2019. http://hdl.handle.net/11449/183606.

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Orientador: James Venturini
Resumo: Devido ao crescente isolamento de espécimes de Klebsiella pneumoniae resistentes a praticamente todas as classes de drogas antimicrobianas, a busca por novas drogas que sejam alternativa terapêutica para o tratamento das infecções por eles causadas se torna relevante. Nesse contexto, a complexação de íons metálicos a drogas antimicrobianas é uma das abordagens empregadas, uma vez que é possível gerar novas drogas com atividade superior as drogas já existentes. No presente estudo, foi realizada a síntese de metalofármaco por reação de coordenação entre sulfato de polimixina B e cobre (II). O produto desta reação foi caracterizado e sua atividade antimicrobiana frente a espécimes de K. pneumoniae resistentes aos carbapenêmicos e à polimixina B foi avaliada. Os resultados demonstraram que as concentrações inibitórias mínimas (MIC) do complexo sintetizado foram menores em relação aos MICs de polimixina B para 44,44% dos espécimes avaliados; para 33,33% dos espécimes os MIC’s foram equivalentes, e para 22,23% dos espécimes os MIC’s do complexo foram superiores aos MIC’s da polimixina B. Esses resultados são promissores, uma vez que houve um incremento na atividade bacteriana da polimixina complexada ao metal para quase metade dos espécimes avaliados, mostrando que a síntese de novas drogas antimicrobianas através da complexação de íons metálicos é uma técnica que deve ser mais explorada. Além disso, nossos resultados devem conduzir a novos estudos que visem a melhor compreensão da... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Due to the increasing isolation of Klebsiella pneumoniae specimens resistant to virtually all classes of antimicrobial drugs, the research for new drugs that are alternative therapeutics for the treatment of infections caused by them becomes relevant. In this context, the complexation of metal ions to antimicrobial drugs is one of the approaches used, since it is possible to generate new drugs with higher activity than existing drugs. In the present study, metallodrugs synthesis was performed by a coordination reaction between polymyxin B sulfate and copper (II). The product of this reaction was characterized and its antimicrobial activity against specimens of K. pneumoniae resistant to carbapenems and polymyxin B was evaluated. The results showed that the minimum inhibitory concentrations (MIC) of the synthesized complex were lower than the polymyxin B MICs for 44.44% of the evaluated specimens; for 33.33% of the specimens the MICs were equivalent, and for 22.23% of the specimens the MICs of the complex were superior to the MICs of polymyxin B. These results are encouraging, since there was an increase in the bacterial activity of metal complexed polymyxin for almost half of the evaluated specimens, showing that the synthesis of new antimicrobial drugs through the complexation of metallic ions is a technique that should be further explored. In addition, our results should lead to further studies aiming to a better understanding of the structure, mechanisms of action, toxicit... (Complete abstract click electronic access below)
Mestre

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Chacra, Nádia Araci Bou. "Otimização de sistema conservante para suspensão oftálmica de dexametasona e polimixina B." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/9/9139/tde-27112007-101637/.

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Um dos grandes desafios no desenvolvimento de fórmulas farmacêuticas e cosméticas é a adequação de seus sistemas conservantes. No presente trabalho, empregou-se método de otimização destes para suspensão oftálmica de dexametasona e sulfato de polimixina B. O experimento foi conduzido utilizando-se planejamento estatístico do tipo simplex-lattice. A matriz de ensaio contemplou 17 fórmulas sendo que as variáveis independentes foram as concentrações de conservantes álcool feniletílico (X1) e digluconato de clorhexidina (X2) e EDTA (X3). A variável dependente ou resposta foi o valor D obtido do desafio das fórmulas com Pseudomonas aeruginosa, Pseudomonas cepacia, Staphy/ococcus aureus, Candida albicans e Aspergillus niger, empregando-se nas determinações, o Método de Regressão Linear. A análise estatística dos resultados, para cada microrganismo desafiante, conduziu à equações que expressaram matematicamente o fenômeno observado. Como conseqüência, foi possível o cálculo teórico do valor D em função das concentrações das variáveis independentes. Além das equações, obtiveram-se as superfícies de resposta e gráficos de contorno correspondentes aos ensaios, para cada germe. Para a seleção da fórmula ou região que atendesse o critério adotado e que conciliasse as condições ideais e factíveis (D ≤ 4 horas, para bactérias e D ≤ 28 horas, para fungos) utilizaram-se duas estratégias: gráfica e numérica. A primeira consistiu na sobreposição dos gráficos de contorno resultando em região da qual selecionou-se, aleatoriamente, a fórmula empregando X1 = 0,10; X2 = 0,80; X3 = 0,10. A segunda, baseou-se na aplicação da função \"desejo\", tendo sido a fórmula ideal resultante de cálculos desenvolvidos, a partir de premissas, sendo: X1 = 0,25; X2= 0,75; X3= 0,0. Ambas as fórmulas, derivadas das estratégias empregadas, foram submetidas à avaliação de seus sistemas conservantes 232 pelo método de Regressão Linear. Os valores D obtidos foram semelhantes àqueles calculados por meio das equações anteriormente mencionadas, exceto para Staphy/ococcus aureus. A aplicação de métodos de otimização estatística permitiu, de forma racional, atingir o objetivo fixado. Através dessas técnicas, tornou-se possível a definição de regiões experimentais em melhores condições, demonstrando vantagens no uso do álcool feniletílico, bem como um melhor conhecimento dos mecanismos envolvidos.
One of the greatest challenges in pharmaceutical and cosmetic formulations consist of the development of adequate preservative systems. Whose optimized development was preposed for ophthalmic suspension of dexametasone and polymyxin B. This was performed threugh simplex-lattice method. The matrix of essay completed 17 formulas, from which independent variables were the preservative concentrations: phenylethanol (X1), chlorhexidine digluconate (X2) and EDTA (X3). The dependent variable was the D-value obtained from the challenge of those formulas with Pseudomonas aeruginosa, Pseudomonas cepacia, Staphhylococcus aureus, Candida albicans and Aspergillus niger, ali result of the Linear Regression Method. The statistical analysis employment led to polynomial expressions which expressed mathematically the observed behavior in each organismo As a consequence the theoretical calculation of the D-value considering ali the independent variables was possible. Besides these expressions, the response surfaces and the contour graphics corresponding to the essays, for each microorganism, were obtained. To the formula or region selection which better complied to the adopted criteria and conciliated ideal and realistic conditions (D ≤ 4 hours, for bacteria and D ≤ 28 hours, for fungi) both graphic and numeric strategies were used. The former consisted of the superposition of contour graphics of each micreorganism, what resulted in a region from which the formula was randomly selected using X1 = 0,10; X2 = 0,80; X3 = 0,10. The latter was based on the application of \"wish\" function, and the ideal formula obtained from calculations developed from these premisses: X1 = 0,25, X2 = 0,75; X3 = 0,0. Both formulas, derived from the employed strategies were submitted to evaluation of their preservative systems by Linear Regression Method. The D-values obtained were similar to those calculated through the previously mentioned expressions, except for Staphylococcus aureus. The application of optimized statistical methods enabled us, in a rational way, to achieve the fixed goal. Through these techniques, both experimental regions in better conditions, demonstrating advantages of using of the involved mechanisms were attained.

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Dezoti, Cassiane. "A enzima Heme Oxigenase-1 na lesão renal aguda oxidativa pela Polimixina B." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/7/7139/tde-07052009-095048/.

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A Lesão Renal Aguda (LRA) tóxica se caracteriza por insulto tubular direto liberando espécies reativas de oxigênio (EROs) e estimulando processos pró-inflamatórios. Neste estudo foram investigadas a toxicidade do Sulfato de Polimixina B (PmxB), antibiótico catiônico usado para o tratamento de infecções por germes gram-negativos e a participação da enzima Heme Oxigenase-1 (HO-1), que tem efeito anti-apoptótico, antiinflamatório e outros. Foram utilizados ratos Wistar, adultos, machos, pesando entre 250-300g. Os animais foram distribuídos nos grupos: Salina (controle, animais que receberam 3ml/Kg de NaCl 0,9% intraperitoneal (i.p.), uma vez ao dia, 5 dias); PmxB (animais que receberam PmxB 40.000U/kg/dia, i.p., uma vez ao dia, 5 dias); Hemin (indutor da HO-1, 1mg/100g, i.p., uma vez ao dia, 5 dias); Protoporfirina de Zinco (ZnPP) (inibidor da HO-1, 50 umol/Kg, i.p., uma vez ao dia, 5ºdia); PmxB+Hemin; PmxB+ZnPP; PmxB+Hemin+ZnPP. Foram avaliados a função renal (FR) (clearance de creatinina, método de Jaffé), a excreção de peróxidos urinários (PU, FOX-2); TBARS urinários; tióis no tecido renal, atividade da catalase (AC) e foi realizada análise histológica no tecido renal. Os resultados mostraram que a PmxB induziu redução da FR com elevação de PU e TBARS, acompanhados por redução de AC e tióis: O tratamento com indutor da HO-1 reverteu a lesão pela PmxB, com melhora da FR e dos parâmetros de peroxidação. A associação do PmxB com o inibidor ZnPP demonstrou aumento da área intersticial relativa (AIR) no tecido renal com achatamento das células tubulares e pontos de necrose no córtex renal. Os resultados diferenciados de FR e peroxidação lipídica, nas técnicas de mensuração utilizadas, confirmaram a participação da heme oxigenase como antioxidante desse modelo de toxicidade renal
Toxic Acute Kidney Injury (AKI) consists on direct injury in the renal tubules liberating reactive oxygen species (ROS) and estimulating inflamatory processes. In this experimental study it was investigated the toxicity of Polymyxin B Sulfate (PmxB), which is a cationic antibiotic used to treat gram-negative infections and the role of the heme oxygenase enzyme (HO-1), with anti-apoptotic and anti-inflamatory effects, in this injury. Adult male Wistar rats, weighing 250-300g were used. The animals were divided into the following groups: Saline (control, animals that received 3ml/Kg of NaCl 0,9% intraperitoneal (i.p.), once a day, 5 days); PmxB (animals that received PmxB 40.000U/kg/dia , i.p., once a day, 5 days); Hemin (HO-1 inducer , 1mg/100g, i.p., once a day, 5 days); Zinc protoporphyrin (ZnPP) (HO-1 inhibitor, 50 umol/Kg, i.p., once a day, 5ºday); PmxB+Hemin; PmxB+ZnPP; PmxB+Hemin+ZnPP. Renal Function (RF) (creatinine clearance, Jaffé method), urinary peroxides (UP, FOX-2), urinary TBARS, thiols in the renal tissue, activity of catalase enzyme (CA) and histology of renal tissue were performed. The results showed that PmxB reduced RF with increment in the UP and TBARS associated to the reduction in the CA and thiols. The HO-1 ameliorated these paramethers. The association PmxB with ZnPP increased relative intersticial area (RIA) of renal tissue with acute tubule necrosis in the renal cortex. The obtained data on RF and lipid peroxidation, with the methods used in the study, confirmed the antioxidant role of the heme oxygenase in this model of renal injury

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Harper, Nigel Murray. "Comparing the mannitol-egg yolk-polymyxin agar plating method to the three tube most probable number method for enumeration of bacillus cereus spores in raw and high-temperature-short-time pasteurized milk." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1683.

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França, Josiane. "Avaliação da segurança de polimixina B em altas doses para o tratamento de infecções causadas por bacilos gram-negativo multirresistentes." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/171399.

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Base teórica: O surgimento de bactérias multirresistentes levou a uma renovação no interesse de antigos antimicrobianos, como a polimixina B, medicamento que foi descartado no passado devido sua toxicidade. Nas últimas duas décadas, esse antimicrobiano tornou-se um dos mais importantes agentes terapêuticos para o tratamento de infecções causadas por bactérias multirresistentes; porém, ainda faltam estudos clínicos que avaliem a segurança da polimixina B, especialmente em altas doses. Objetivo: Avaliar eventos adversos graves relacionados à infusão e a falência renal nos pacientes que receberam altas doses de polimixina B intravenosa. Métodos: Realizamos um estudo de coorte retrospectivo, multicêntrico. Incluímos pacientes que receberam > 3mg/kg/ dia ou uma dose total ≥250mg/dia de polimixina B, no período de janeiro de 2013 a dezembro de 2015. Para a avaliação dos eventos relacionados a infusão, foram incluídos pacientes que receberam ≥ 1 dose de polimixina B e para avaliação de falência renal incluiu apenas os pacientes que receberam ≥ 48 horas de polimixina B. Os desfechos principais avaliados foram os eventos adversos graves relacionados à infusão de acordo com os Critérios de Terminologia Comuns para Eventos Adversos (CTCAE v4.0) e a falência renal, utilizamos os critérios RIFLE (Risk, Injury, Failure, Loss and End stage), para categorizar os diferentes graus de lesão renal aguda. As variáveis incluídas no estudo foram as variáveis demográficas (idade, sexo), as variáveis individuais (peso, comorbidades, escore de Charlson), os fatores de gravidade (internação em UTI, uso de vasopressor, uso de bloqueador neuromuscular), outras fármacos nefrotóxicas, dose de polimixina utilizada (total, média diária e em mg/kg/dia), associação com outros medicamentos, e características da infecção (sítio, isolamento microbiológico) foram avaliadas em análise bivariada. Variáveis com P≤0.2 foram incluídas uma a uma, em ordem crescente, em modelo de regressão de COX. Variáveis com P< 0.1 permaneceram no modelo final. Resultados: Foram incluídos 222 pacientes para análise de eventos graves relacionados à infusão. A dose média de polimixina B foi de 3.61± 0.97 mg/kg /dia (dose total media = 268 mg/kg). Ocorreram eventos adversos graves relacionados à infusão em dois pacientes, determinando uma incidência bruta de 0.9% (intervalo de confiança de 95%, 0.2-3.2): um 7 evento classificado como um risco ameaçador a vida (efeito adverso classe IV) ocorreu em um paciente, homem, de 40 anos, internado no Centro de Terapia Intensiva, com fibrose cística, que recebeu 3,3 mg / kg / dia de PMB e desenvolveu dor torácica súbita, dispnéia e hipoxemia, no quarto dia de tratamento e o outro evento adverso grave (classe III), ocorreu em um paciente, homem, 23 anos, internado na enfermaria, com linfoma, que recebeu 3,6 mg / kg / dia de PMB , que apresentou parestesia perioral, tonturas e dispnéia no primeiro dia de tratamento. A falência renal foi analisada em 115 pacientes que receberam ≥ 48 horas de polimixina B e que não estavam em diálise no início do tratamento com Polimixina B; Falência renal foi encontrada em 25 de 115 (21,7%) pacientes expostos as PMB. Nosso estudo identificou que 54 [47,0%] pacientes desenvolveram algum grau de lesão renal aguda, pelos critérios de RIFLE: risco, 15 (27,8%), injúria, 14 (25,9%) e falência, 25 (46,3%) dentro das categorias do RIFLE. Além disso, droga vasoativa, outros fármacos nefrotóxicos e clearance de creatinina foram fatores de risco independentes para falência renal. Nem a dose diária de polimixina B ajustada para o peso corporal, nem a dose diária total foram associadas a falência renal. A mortalidade intra-hospitalar foi de 60% (134 pacientes): 26% (57 pacientes) morreram durante o tratamento e nenhum óbito foi durante a infusão. Conclusão: Altas doses de polimixina B no tratamento de infecções por bactérias gramnegativo apresentaram incidência baixa de eventos adversos agudos no nosso estudo e incidência de nefrotoxicidade elevadas, mas semelhantes a alguns estudos prévios com doses usuais”. Portanto, doses elevadas podem ser testadas em ensaios clínicos, objetivando melhorar os desfechos dos pacientes gravemente doentes com infecções por bactérias multirresistentes e minimizar o surgimento da resistência a polimixina B.
Background: The emergence of multiresistant bacteria has led to a renewal in the interest of old antimicrobials, such as polymyxin B, a drug that has been discarded in the past due to its toxicity. However, at this time, this antimicrobial has become one of the most important therapeutic agents for the treatment of infections caused by multiresistant bacteria but there is still a lack of clinical studies that evaluate the safety of polymyxin B, especially in relation to the use of high doses. This strategy, high doses, may be necessary in the fight against Gramnegative bacteria with a high minimum inhibitory concentration. Patients and methods: A retrospective, multicenter cohort study; the period evaluated was from January 2013 to December 2015, included patients who received > 3mg/kg/day or a total dose of ≥250mg/day of polymyxin B. The study included the evaluation of infusion-related events, patients who received ≥ 1 dose of polymyxin B and patients who received ≥ 48 hours of PMB were included for evaluation of renal failure. Major outcomes were serious adverse events related to infusion according to the Common Terminology Criteria for Adverse Events (CTCAE v4.0) and categorized renal failure by the RIFLE criteria (Risk, Injury, Failure, Loss, End stage). Factors potentially related to nephrotoxicity or mortality in 30 days were: demographic variables (age, sex), individual variables (weight, comorbidities, Charlson score), severity factors (ICU admission, use of vasopressor, use of Neuromuscular blocker), nephrotoxicity (other nephrotoxic drugs), polymyxin dose (total, daily mean and mg / Kg / day), association of drugs and infection characteristics (site and microbiological isolate) were evaluated in bivariate analysis. Variables with P≤0.2 were included one by one, in ascending order, in a Cox regression model. Variables with P <0.1 remained in the final model. Results: Two of 222 patients presented a severe infusion-related adverse event during PMB infusion, resulting in a crude incidence of 0.9% (95% Confidence Interval [CI], 0.2-3.2); one was classified as life-threatening and one classified as severe (crude incidence of each adverse event, 0.45%; 95% CI, 0.08-2.5). The life-threatening adverse effect occurred in an ICU patient (crude incidence among ICU patients, 0.67%; 95% CI, 0.12-3.7), a 40-years old male with cystic fibrosis who used 3.3 mg/kg/day of PMB and developed sudden thoracic pain, dyspnea and hypoxemia, in the fourth day of treatment. The severe adverse effect occurred in a non-ICU patient (crude incidence among non-ICU patients, 1.3%; 95% CI, 0.2-7.2), a 23- years old male with lymphoma exposed to 3.6 mg/kg/day of PMB, who presented perioral 9 paresthesia, dizziness and dyspnea in the first day of treatment. Renal failure was analysed in 115 patients who received ≥48 hours of PMB and who were not previously in dialysis. A total of 54 [47.0%] patients developed any degree of AKI, categorised as Risk [27.8%]; Injury [25.9%] and Failure [46.3%]) and 25 of 115 (21.7%) patients presented renal failure Vasoactive drug, concomitant nephrotoxic drugs and baseline creatinine clearance were independent risk factors for renal failure. Neither PMB daily dose scaled by body weight nor total daily dose were associated with renal failure. In-hospital mortality was 60% (134 patients): 26% (57 patients) occurred during treatment and none during infusion. Conclusion: Results suggest that high dose regimens have similar safety profile of usual doses and could be further tested in clinical trials assessing strategies to improve patients’ outcomes and minimize the emergence of PMB resistance.

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Bechet, Emmanuelle. "Étude structurale et fonctionnelle de tyrosine-kinases bactériennes." Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00720223.

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Au laboratoire, une famille de tyrosine kinases propres aux bactéries et ne présentant aucune ressemblance structurale avec les protéine-kinases d'origine eucaryote a été identifiée. Ces enzymes, appelées BY-kinases, sont notamment impliquées dans la biosynthèse des polysaccharides extracellulaires, mais leurs rôles précis ainsi que leurs mécanismes catalytiques sont encore peu compris.Dans la première partie de ce travail, nous avons caractérisé le rôle physiologique de la phosphorylation sur la tyrosine de la protéine Ugd, une UDP-glucose déshydrogénase, par les BY-kinases Wzc et Etk d'E. coli. Nous avons démontré que la phosphorylation d'Ugd sur un site commun à Wzc et Etk augmente son activité. Nous avons également établi que la phosphorylation d'Ugd par Wzc participe à la régulation de la quantité d'acide colanique produit, tandis que la phosphorylation d'Ugd par Etk influence la résistance de la bactérie à la polymyxine.Nous avons également effectué une analyse structure-fonction du domaine cytoplasmique de deux BY-kinases, CapA1/CapB2 de S. aureus et Wzc d'E. coli. Nous avons montré que ces deux protéines s'associent en octamère, grâce au motif EX2RX2R et qu'elle s'autophosphoryle selon un mécanisme intermoléculaire. Nous avons, de plus, identifié le mécanisme d'activation de ces protéines et révélé l'importance d'un domaine particulier dans l'autophosphorylation de Wzc et la biosynthèse de l'acide colanique.La caractérisation structurale et fonctionnelle des BY-kinases représente une approche prometteuse et originale en vue de l'élaboration de molécules inhibant spécifiquement leur activité et pouvant affecter le pouvoir virulent des bactéries pathogènes.

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Carneiro, Marcelo. "Terapia com polimixina B em infecção de corrente sanguínea por bacilos Gram-negativos multirresistentes." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/118338.

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Introdução: As polimixinas são consideradas as opções terapêuticas de resgate para o tratamento das infecções de corrente sanguínea (ICS) por bacilos Gram-negativos (BGN) com resistência aos carbapenens (CR) e a combinação com outro antimicrobiano tem sido utilizada apesar da falta de evidência clínica para esta prática. Objetivo: Avaliar o uso de polimixina B intravenosa em monoterapia e em combinação com outro antimicrobiano para ICS por BGN CR. Pacientes e Métodos: Foi um estudo de coorte retrospectivo em um hospital terciário, incluindo 99 pacientes. A comparação dos tipos terapias foi através do propensity score. Resultados: A mortalidade global em 30 dias foi de 43,4%: 40,7% (24 de 59) e 47,5% (19 de 40), p=0,51, em pacientes que receberam combinação e monoterapia, respectivamente. A sepse grave/choque séptico no dia da ICS, alta pontuação do escore de bacteremia de Pitt e a presença de neoplasia como doença de base foram, independentemente, associados a maior mortalidade em 30 dias no modelo de regressão de Cox. A terapia combinada não foi significativamente associada a este resultado (hazard ratio, 0,70; intervalo de confiança de 95%, 0,36-1,36); p=0,29). Apesar de não ser significativa, houve uma tendência a um efeito benéfico da associação em pacientes com ICS por BGN CR da família Enterobacteriaceae. Não houve diferença no desenvolvimento de insuficiência renal aguda em pacientes que receberam terapia de combinação comparado com os que receberam monoterapia. Conclusão: Não houve diferença na mortalidade em 30 dias em pacientes com ICS por BGN CR tratados com polimixina B em combinação com outro antimicrobiano ou em monoterapia. A prática rotineira de combinar um segundo antibiótico em esquemas baseados em polimixinas, especialmente, se a bactéria apresenta resistência in vitro ao carbapenem, ainda necessita estudos clínicos adicionais.
Background: Polymyxins are usually the last resort therapy for carbapenem-resistant Gram-negative bacteria (CR GNB) bloodstream infections (BSIs), combination with another antimicrobial has been used despite the lack of clinical evidence supporting such practice. Objetive: We aimed to assess the use of intravenous polymyxin B in combination with another antimicrobial in comparison with polymyxin B as a single drug for CR GNB BSIs, adjusting for a propensity score for indication of combination therapy. Patient and methods: We compared combination versus monotherapy with polymyxin B for CR GNB BSIs, adjusting for a propensity score for indication of combination therapy. It was a retrospective cohort study at a tertiary-hospital including 99 patients. Results: The overall 30-day mortality was 43.4%: 40.7% (24 of 59) and 47.5% (19 of 40), P=0.51, in patients receiving combination and monotherapy, respectively. Severe sepsis/ septic shock at BSI onset higher Pitt bacteremia score and neoplasia were independently associated with higher 30-day mortality in a Cox-regression model. Combination therapy was not significantly associated with this outcome (Hazard Ratio, 0.70; 95% confidence interval, 0.36-1.36); P=0.29). Although not significant, there was a tendency to a beneficial effect of combination in patients with Enterobacteriaceae CR GNB BSIs. There was no difference in development of AKI in patients receiving combination therapy compared to those receiving monotherapy. Conclusions: There was no difference in 30-day mortality in patients with CR GNB BSIs treated with polymyxin B in combination with another antimicrobial compared with polymyxin B alone. The routine practice of combining a second antibiotic in polymyxins-based regimes, especially if the bacteria present in vitro resistance to the agent, still lacks support from clinical studies.

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Aranzana-Climent, Vincent. "Apport de la modélisation semi-mécanistique dans l'étude pharmacocinétique/pharmacodynamique des antibiotiques seuls et en combinaison dans la lutte contre les bactéries résistantes." Thesis, Poitiers, 2019. http://theses.univ-poitiers.fr/62724/2019-Aranzana-Climent-Vincent-These.

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La lutte contre les bactéries multirésistantes est une priorité majeure définie par l’Organisation Mondiale de la Santé, puisque les dernières prédictions estiment que les infections par des bactéries multirésistantes feront plus de morts que le cancer d’ici 2050. Dans le contexte actuel, avec un faible nombre de nouveaux antibiotiques mis sur le marché pour lutter contre les bactéries multirésistantes, il est important de d’optimiser l’utilisation des antibiotiques à notre disposition. C’est dans ce but que les modèles semi-mécanistiques servant à analyser les résultats d’études de PK/PD des antibiotiques peuvent être développés. Ces outils mathématiques permettent de quantifier les relations concentration-effet, de molécules seules ou de combinaisons de molécules afin d’optimiser leur efficacité, prévenir les résistances et donc prolonger la durée de vie des antibiotiques. Dans ce travail, après une présentation des méthodes d’étude de la PK/PD des antibiotiques seuls et en combinaison, les résultats de deux projets sont présentés :1. Une étude de la PK/PD de la céfoxitine contre une souche de Mycobacterium abscessus. Dans une première partie, il a été montré que l’administration de la céfoxitine par nébulisation permet d’obtenir des concentrations pulmonaires 1000 fois plus importantes qu’après une administration intraveineuse, faisant de la céfoxitine un bon candidat à la nébulisation. Dans la seconde partie un modèle PK/PD semi-mécanistique a été développé à partir de données in vitro, ce qui permet d’identifier la relation concentration-effet pour deux sous-populations bactériennes tout en tenant compte de la dégradation de la molécule.2. Une étude de la PK/PD de l’association polymyxine B et minocycline contre une souche d’Acinetobacter baumannii résistante à la polymyxine B. Cette étude in vitro comprend des données de bactéricidie avec suivi de la densité de bactéries résistantes à la polymyxine B, enrichies d’expériences complémentaires servant à préciser les caractéristiques de cette sous-population résistante. Ces données ont toutes été analysées par modélisation PK/PD semi-mécanistique, ce qui a notamment permis de quantifier l’importance de l’interaction entre les deux molécules et de formuler des hypothèses sur les mécanismes de cette interaction
Fighting against multidrug-resistant bacteria is a major priority set by World Health Organisation, since it is forecasted that multi-drug-resistant bacteria will be responsible for more deaths than cancer by 2050. In the current context, with only a few new antibiotic drugs active against multidrug-resistant bacteria approved every year, it is of importance to optimize the use of already available antibiotics. It is with this goal in mind, that semi-mechanistic models used to analyse results from PK/PD studies of antibiotics, can be developed. These mathematical tools enable quantification of concentration-effect relationships of drugs, used alone or in combination, in order to optimize their efficacy, prevent bacterial resistance, thus lengthening the period of usability of antibiotics. In this work, after a presentation of the methods used to study PK/PD of antibiotics alone and in combination, results from two projects are presented:1. A study of cefoxitin PK/PD against a Mycobacterium abscessus strain. Firstly, it was shown that after nebulisation of cefoxitin, pulmonary concentrations were 1000-fold higher than after intravenous administration, making cefoxitin a good candidate for nebulisation. In a second part, a semi-mechanistic PK/PD model was developed from in vitro data, enabling identification of concentration-effect relationships for two bacterial sub-populations while taking into account degradation of cefoxitin. 2. A study of the PK/PD of polymyxin B and minocycline association against a polymyxin B resistant Acinetobacter baumannii strain. This in vitro study incorporates data from time-kill experiments with quantification of a bacterial sub-population resistant to polymyxin B, enriched by complementary experiments providing information on the characteristics of this resistant sub-population. This data was analysed by semi-mechanistic PK/PD modelling, which made possible quantification of the strength of interaction between the two drugs and to form hypotheses about the mechanisms of the observed interaction

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Lew, Cynthia S. "Loss of the Lipopolysaccharide Core Biosynthesis rfaD Gene Increases Antimicrobial Chemokine Binding and Bacterial Susceptibility to CCL28 and Polymyxin: A Model for Understanding the Interface of Antimicrobial Chemokines and Bacterial Host Defense Avoidance Mechanisms." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3756.

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In order to better understand the mechanism of antimicrobial chemokine activity, including binding to and killing of bacteria, random transposon mutagenesis was performed in Yersinia pseudotuberculosis. Resulting mutants were screened for increased binding to chemokine and high binding clones were selected for further study. One mutant, designated mutant 27, was found to have a single insertion mutation in the rfaD gene. The rfaD gene product is involved in heptose biosynthesis, one of the sugars of the inner core oligosaccharide of Gram- negative lipopolysaccharide (LPS). Mutant 27 was found to bind both CCL25 and CCL28, two antimicrobial chemokines, more efficiently than the wild type bacteria. This clone was also found to be more susceptible to CCL28- mediated killing and polymyxin activity. Complementation with a plasmid bearing the full rfaDFC operon restored the wild type phenotype in both regards. These data suggest that normal LPS expression by Y. pseudotuberculosis serves to protect the bacteria from the antimicrobial function of chemokines and other antimicrobial proteins of the mammalian innate immune system.

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Bartolleti, Flávia. "Avaliação da relação genética e perfil de sensibilidade de Klebsiella pneumoniae resistentes à polimixina B." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/9/9136/tde-21122016-103009/.

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INTRODUÇÃO: O aumento da incidência de infecções causadas por bactérias resistentes a múltiplos antimicrobianos limita cada vez mais as opções terapêuticas, dificultando o tratamento e aumentando os índices de morbidade e mortalidade, além dos gastos em saúde. Ao longo dos últimos cinco anos, essa limitação tem levado ao reestabelecimento do uso de antimicrobianos consideradas ultrapassados, como as polimixinas. Este grupo passou a ser utilizado com cada vez mais frequência no tratamento de infecções causadas por microrganismos gram-negativos resistentes aos carbapenêmicos. As enterobactérias, em particular a espécie Klebsiella pneumoniae, tem apresentado frequentemente esse perfil, porém, a resistência à polimixinas têm sido relatada, eliminando essa importante alternativa terapêutica. Apesar da importância do tema, são escassas as publicações sobre frequência de resistência às polimixinas em K. pneumoniae e a relação clonal entre isolados resistentes à polimixina B no Brasil. OBJETIVOS: Avaliar a relação genética, perfil de sensibilidade antimicrobiana e mecanismos de resistência às polimixinas em K. pneumoniae. MATERIAIS E MÉTODOS: A execução deste trabalho dividiu-se em duas partes principais: (i) levantamento de dados de culturas positivas para K. pneumoniae da rotina de pacientes hospitalizados em instituições atendidas pelo serviço de análises clínicas do Fleury Medicina e Saúde; (ii) confirmação das concentrações inibitórias mínimas (CIM) para polimixina B, avaliação da relação clonal por eletroforese em campos pulsados (PFGE),e sequenciamento de múltiplos loci (MLST), avaliação da integridade do gene mgrB e da presença do gene mcr-1 por PCR entre isolados resistentes à polimixina B e aos carbapenêmicos (CPRKp). RESULTADOS e CONCLUSÕES: Na análise de 3.085 isolados de K. pneumoniae obtidos de pacientes internados em 11 hospitais da Grande São Paulo entre os anos de 2011 e 2015, foi evidenciado um aumento estatisticamente significativo na resistência aos carbapenêmicos de 6,8% em 2011 para 35,5% em 2015. Em 2015, KPC foi detectada em 96,2% dos isolados resistentes aos carbapenêmicos. A distribuição das concentrações inibitórias mínimas de polimixina B entre todos os isolados de K. pneumoniae evidenciou uma distribuição bimodal com a CIM de 2 mg/L como o valor de ponto de corte para a susceptibilidade à polimixina B; assim, 3,6% do número total de isolados sensíveis aos carbapenêmicos foram interpretados como resistentes enquanto essa proporção foi de 22,5% entre as resistentes aos carbapenêmicos (CRKp). Entre esses últimos isolados também houve um aumento estatisticamente significativo na tendência anual de resistência à polimixina B, de 0% em 2011 para 27,1% em 2015. Estas taxas variaram de 0,7% em 2011 para 3,9% até junho de 2014 entre os sensíveis aos carbapenêmicos. Entre os antimicrobianos alternativos, a amicacina e a tigeciclina foram os compostos mais ativos. A análise por PFGE de 60 isolados de CPRKp obtidos de pacientes distintos nos anos de 2014 e 2015 evidenciou dois grandes grupos clonais: CPRKp1 e CPRKp2, os quais segundo a análise por MLST pertencem, respectivamente, aos grupos ST11 e ST437, ambos do complexo clonal 258. Foi observado o mesmo grupo ST entre isolados obtidos dentro de um mesmo hospital e também entre diferentes hospitais, públicos e privados. O mecanismo de resistência mais comum entre os isolados de CPRKp foi a presença de sequências de inserção interrompendo o gene mgrB. O gene mcr-1 não foi detectado em nenhum dos isolados.
INTRODUCTION: The increasing incidence of infections caused by bacteria resistant to multiple antimicrobials increasingly limits therapeutic options, making treatment difficult and increasing the morbidity and mortality and health spending. Over the past five years, this limitation has led to the reestablishment of the use of antimicrobials deemed outdated, such as polymyxins. This group is now used with increasing frequency to treat infections caused by carbapenem-resistant gram-negative microorganisms. Enterobacteria, especially Klebsiella pneumoniae, have often presented this profile, however, resistance to polymyxins have been also reported, eliminating this important therapeutic alternative. Despite the importance of this issue, the publications are scarce on the polymyxins resistance frequency in K. pneumoniae and clonal relationship among isolates resistant to polymyxin B in Brazil. OBJECTIVES: To evaluate the genetic relationship, antimicrobial susceptibility profile and polymyxin B resistance mechanisms in K. pneumoniae. MATERIALS AND METHODS: The execution of this work was divided into two main parts: (i) survey data on routine cultures positive for K. pneumoniae from patients hospitalized in institutions attended by the clinical analysis service of Fleury Health and Medicine; (ii) confirmation of to polymyxin B minimum inhibitory concentrations (MIC), evaluation of clonal relationship by electrophoresis pulsed field gel electrophoresis (PFGE), multilocus sequence typing (MLST), evaluation of the integrity of the mgrB gene and the presence of mcr-1 gene by PCR among isolates resistant to polymyxin B and carbapenems (CPRKp). RESULTS AND CONCLUSIONS: The analysis of 3,085 K. pneumoniae isolates obtained from inpatients from 11 hospitals in the São Paulo urban area between 2011 and 2015, has shown a statistically significant increase in carbapenem resistance from 6.8% in 2011 to 35.5% in 2015. In 2015, KPC was detected in 96.2% of isolates resistant to carbapenems. The polymyxin B MIC distribution of all Klebsiella pneumoniae showed a bimodal distribution with the MIC of 2 mg/L as the cutoff value for polymyxin B susceptibility; thus, 3.6% of the total number of isolates susceptible to carbapenems were interpreted as resistant while this proportion was 22.5% among carbapenem-resistant isolates (CRKp). Among these isolates there was also a statistically significant increase in the annual trend of polymyxin B resistance, from 0% in 2011 to 27.1% in 2015. These rates ranged from 0.7% in 2011 to 3.9% by June 2014 between carbapenem-susceptible isolates. Among alternative antimicrobials, amikacin and tigecycline were the most active compounds. The analysis by PFGE of 60 CPRKp isolates obtained from different patients in the years 2014 and 2015 showed two major clonal groups: CPRKp1 and CPRKp2, which according to the analysis by MLST belong respectively to ST11 and ST437 groups, both from clonal complex 258. We observed the same ST group of isolates obtained within a hospital and between different public and private hospitals. The most common mechanism of polymyxin B resistance among CPRKp isolates was the presence of insertion sequences interrupting the mgrB gene. The mcr-1 gene was not detected in any of the isolates.

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Neiva, Luciana Barros de Moura. "Toxicidade da polimixina B em células LLC-PK1 e a enzima heme oxigenase-1." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/7/7139/tde-07052009-112206/.

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Na lesão renal aguda, os mecanismos de defesa atuam como genes protetores, como a proteína heat shock 32 (HSP 32), também conhecida como heme oxigenase-1 (HO-1). A polimixina B (PmxB) é um antimicrobiano nefrotóxico. O objetivo deste estudo foi caracterizar a participação da enzima HO-1 na toxicidade da PmxB em células LLC-PK1. As células foram submetidas aos seguintes tratamentos: Controle (CTL- 0µM); Hemin (indutor de HO-1, 25µM); Hemin II (250M), Protoporfirina de zinco (ZnPP - inibidor de HO-1, 10M,); Nitro-L-arginina-metilester (L-NAME - inibidor de iNOS, 0,1mM); PmxB (375µM); PmxB + Hemin (25µM de Hemin uma hora antes da PmxB); PmxB + ZnPP (10M de ZnPP uma hora antes da PmxB); PmxB + Hemin + L-NAME (25M de Hemin e 0,1mM de L-NAME uma hora antes da PmxB). Os grupos foram avaliados em 24 e 72 horas. Foram analisados os seguintes parâmetros: desidrogenase láctica (DHL), peroxidação lipídica (MDA), expressão gênica da HO-1 por RT-PCR, síntese protéica da HO-1 por imunofluorescência, óxido nítrico (NO) pelo método de Griess e expressão protéica da HO-1 e da iNOS por western blotting. Os resultados mostraram que a PmxB elevou o DHL com aumento dos níveis de MDA. O Hemin e a ZnPP elevaram as variáveis DHL, MDA e óxido nítrico (NO). O indutor de HO-1 incrementou a expressão protéica da HO-1 e da iNOS. A PmxB se confirmou como citotóxica e a HO-1 intensificou a lesão por mecanismos oxidativos. O efeito da HO-1 na lesão celular parece ser mediado pelo NO
In the acute kidney injury, the mechanisms of defense act as protector genes, as the protein heat shock 32 (HSP 32), also known as heme oxygenase-1 (HO-1). The polymyxin B (PmxB) is a nephrotoxic antimicrobial. The aim of this study was to distinguish the role of the HO-1 enzyme in the PmxB toxicity in LLC-PK1 cells. The cells were submitted to the following treatments: Control (CTL- 0µM); Hemin (inhibitor of HO-1, 25µM); Hemin II (250M), Zinc protoporphyrin (ZnPP - inhibitor of HO-1, 10M,); NG-nitro-L-arginine methyl ester (L-NAME - inhibitor of iNOS, 0,1mM); PmxB (375µM); PmxB + Hemin (25µM of Hemin one hour before the PmxB); PmxB + ZnPP (10M of ZnPP one hour before the PmxB); PmxB + Hemin + L-NAME (25M of Hemin and 0,1mM of L-NAME one hour before the PmxB). All groups were evaluated in 24 and 72 hours. The following parameters were analysed: lactate dehydrogenase (LDH), lipid peroxidation (MDA), genic expression of HO-1 by RT-PCR, protein syntesis of HO-1 by immunofluorescence, nitric oxide (NO) by Griess method and protein expression of HO-1 and of iNOS by western blotting. The results showed that PmxB increased the LDH and the levels of MDA. Hemin and ZnPP also increased the LDH variables, MDA and nitric oxide (NO). The inducer of HO-1 improved the protein expression of HO-1 and of iNOS. The PmxB was confirmed as a cytotoxic and the HO-1 intensified the failure by oxidative mechanisms. The effect of HO-1 in the cell injury seemed to be mediated by NO

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Teixeira, Jane de Oliveira Gonzaga [UNIFESP]. "Infecção da corrente sanguínea causada por Pseudomonas aeruginosa resistente aos carbapenêmicos: fatores associados a mortalidade e influência da terapia combinada com polimixina B e imipenem." Universidade Federal de São Paulo (UNIFESP), 2011. http://repositorio.unifesp.br/handle/11600/9742.

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Made available in DSpace on 2015-07-22T20:50:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-27
P. aeruginosa é um importante microorganismo em infecções de corrente sanguínea. O tratamento da P. aeruginosa resistente aos carbapenêmicos é um desafio, já que as drogas mais utilizadas para este fim, as polimixinas, tem uma ação inferior aos carbapenêmicos. No entanto, o uso combinado de polimixinas com carbapenêmicos tem demonstrado sinergismo em estudos in vitro. Objetivos: Avaliar a resposta ao tratamento com polimixina B versus polimixina B e imipenem em pacientes com infecção da corrente sanguínea associada a assistência à saúde, primária ou secundária, causada por Pseudomonas aeruginosa resistente aos carbapenêmicos e identificar os fatores associados à mortalidade. Métodos: Realizamos um estudo tipo coorte retrospectivo, com pacientes internados no Hospital São Paulo - UNIFESP, no período de 01 de janeiro de 2000 à 31 de dezembro de 2009. A identificação dos pacientes foi realizada através de levantamento de dados da ficha de notificação de hemoculturas com posterior revisão dos prontuários. Os pacientes foram inicialmente divididos em óbitos e sobreviventes e avaliados quanto a exposição a diversos fatores associados à letalidade hospitalar e relacionada a infecção. Foi realizada pesquisa de metalobetalactamase nas amostras de P. aeruginosa que puderam ser recuperadas, por técnica de biologia molecular. Resultados: Foram estudadas 69 infecções de corrente sanguínea por P. aeruginosa resistente aos carbapenêmicos, das quais 35 foram tratadas com monoterapia com polimixina B e 34 com terapia combinada. O óbito relacionado a infecção, definido como aquele que ocorreu nos primeiros 14 dias do diagnóstico da infecção da corrente sanguínea, foi de 42,8% nos pacientes que utilizaram monoterapia e 44,1% naqueles que utilizaram terapia combinada (p=0,917). Foram fatores associados à mortalidade durante a internação hospitalar, o uso prévio de glicopeptídeos (OR 10,71, IC 1,20-95,34, p=0,033) e o escore de Charlson no momento da internação (OR 1,9, IC 1,22-2,94, p=0,004). Foram variáveis associadas à mortalidade relacionada à infecção, a presença de choque séptico (OR 9,99, IC 1,81- 55,22, p=0,006) e uso de nutrição parenteral (OR 7,45, IC 1,23-45,24, p=0,029). Foi encontrada uma alta taxa de mortalidade. A terapia combinada não modificou a evolução dos pacientes. A mortalidade hospitalar no grupo com monoterapia foi de 77,1% entre os pacientes que receberam monoterapia e 79,4% nos que receberam terapia combinada (p=0,819). Em pacientes tratados com terapia combinada, quando analisada a presença ou não de metalobetalactamase, não houve diferença estatisticamente significativa quanto aos desfechos. Conclusões: Nesta população, foram fatores independentes para o óbito durante a internação o uso prévio de glicopeptídeos e a pontuação no score de Charlson e, para o óbito relacionado à infecção, a presença de choque séptico e o uso de nutrição parenteral. A presença de metalo-beta-lactamase não influiu no desfecho.
Pseudomonas aeruginosa is an important pathogen causing nosocomial bloodstream infections. The treatment of carbapenem-resistant P. aeruginosa is a challenge as the drugs used for this purpose, the polymyxins, have lower activity compared with carbapenems. However, it has been suggested that polymyxins have the ability to make gram-negative bacteria more susceptible to other antibiotics. As carbapenems are considered the main drugs against P. aeruginosa, it would be interesting to demonstrate the efficacy of this combination in vivo, targeting a more effective therapy. Objectives: To evaluate the response of the treatment with polymyxin B versus polymyxin B and carbapenem in patients with nosocomial bloodstream infection caused by carbapenenresistant Pseudomonas aeruginosa and identify factors associated with mortality among those patients Methods: A retrospective cohort study was performed at Hospital São Paulo - UNIFESP, from January 1st, 2000 to December 31, 2009. The identification of patients was done through data collection from the blood cultures report. Patients were initially divided into deaths and survivors, and assessed for exposure to various factors potentially associated with in-hospital mortality and infection-related mortality. Presence of metalobetalactamase was tested trough PCR technique. Results: We studied 69 bloodstream infections caused by carbapenems-resistant P. aeruginosa. Thirthy-five were treated with polymyxin B monotherapy and 34 with combined therapy. In- hospital mortality was 77.1% and 79.4% in the monotherapy group and combined therapy group, respectively (p = 0.819). The infection-related mortality was 42.8% among patients who received monotherapy, and 44.1% in those receiving combined therapy (p = 0.917). Factors associated with mortality were previous use of glycopeptides (OR 10.71, CI95% 1.20 to 95.34, p = 0.033) and Charlson score (OR 1.9, CI95% 1, 22 to 2.94, p = 0.004). Infection-related mortality was associated with the presence of septic shock (OR 9.99, CI95% 1.81 to 55.22, p = 0.006) and parenteral nutrition (OR 7.45, CI95% 1.23 - 45.24, p = 0.029). No statistically significant difference was found between patients with MBLharboring and non-MBL-harboring strains treated with combined therapy. Conclusions: No difference was found between the monotherapy and combined therapy group regarding mortality. Independent factors related to in- hospital mortality were prior use of glycopeptides and the Charlson score. Presence of septic shock and use of parenteral nutrition were independently associated with infection-related mortality.
TEDE
BV UNIFESP: Teses e dissertações

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Antic, Marie-Laure. "Mécanisme d'action des polymyxines." Paris 5, 1990. http://www.theses.fr/1990PA05P103.

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Bardet, Lucie. "Développement de nouveaux outils de détection des bacilles à Gram négatif résistants à la colistine." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0596.

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La découverte récente du premier gène de résistance plasmidique à la colistine mcr-1 a mis en évidence le besoin urgent d'améliorer la détection des isolats résistant à la colistine dans les laboratoires de microbiologie clinique afin de pouvoir rapidement isoler les patients porteurs. L’objectif de ma thèse a ainsi été de répondre à cette problématique par le développement et l’évaluation d’outils spécifiques. Une revue a été rédigée visant à résumer les nouveaux outils développés pour détecter la résistance aux polymyxines, y compris la présentation des méthodes actuelles phénotypiques, antibiogrammes et génotypiques. Le milieu de culture LBJMR a été développé pour détecter toutes les bactéries à Gram négatif résistantes à la colistine et également les souches d’entérocoques résistants à la vancomycine qui représentent un autre problème majeur de santé publique. LBJMR est polyvalent et a permis de dépister 3 bactéries d'intérêt clinique à partir d’un même échantillon: E. coli et K. pneumoniae résistantes à la colistine, et E. faecium résistant à la vancomycine. Un brevet a été déposé. Le kit UMIC Colistine est un dispositif commercial de détermination de la CMI basé sur la méthode de référence. Évalué conformément à la norme ISO 20776, sa sensibilité était excellente pour la détection des souches porteuses du gène mcr-1. Le kit UMIC Colistine constitue ainsi une méthode rapide et fiable pour évaluer la CMI des isolats cliniques dans les laboratoires de microbiologie clinique. Enfin, mes travaux de thèse ont compris l’analyse d’une souche de K. pneumoniae hétérorésistante à la colistine et la description d’une nouvelle espèce bactérienne : Pseudomonas massiliensis
The recent discovery of mcr-1, the first plasmid-mediated colistin resistance gene, highlighted the urgent need to implement the detection of colistin-resistant isolates in clinical microbiology laboratories, in order to isolate carrier patients. My thesis aimed to address this issue by developing and evaluating specific tools. A review was redacted to summarize the new tools developed to detect polymyxin resistance including the current phenotyping, susceptibility testing and genotyping methods. The LBJMR culture medium has been developed to detect all colistin-resistant Gram-negative bacteria and also the vancomycin-resistant enterococci which represent another major problem of public health. The LBJMR medium allowed the detection of different bacteria of interest from the same clinical sample: colistin-resistant E. coli and K. pneumoniae and also a vancomycin-resistant E. faecium. This project led to a patent filing. The UMIC Colistine kit is a ready-to-use device based on the reference method to determine the polymyxin MIC. Evaluated in accordance with ISO 20776 standard, its sensitivity was excellent for the detection of colistin-resistant strains harboring the mcr-1 gene. The UMIC Colistin system is a rapid and reliable method to determine colistin MIC of clinical isolates in clinical microbiology laboratories. My thesis project also included the analysis of a colistin-heteroresistant Klebsiella pneumoniae strain, and the description of a new bacteril species, Pseudomonas massiliensis. These studies highlight the need to improve the detection of colistin-resistant strains by using reliable methods, suitable for diagnosis in clinical microbiology laboratories

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Thomas, Celestine J. "Endotoxin Peptide/Protein Interactions: Thermodynamic And Kinetic Analysis." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/213.

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Endotoxin or Lipopolysaccharide (LPS) is the invariant structural component of gram negative bacterial outer membranes and is the chief causative factor of Sepsis or endotoxic shock. Sepsis is a syndrome that has very high mortality rates even in this age of excellent therapeutics and critical patient care. The treatment for sepsis till date remains nonspecific and supportive due to lack of effective anti-endotoxic drugs. Sepsis is initiated when the circulating bacteria shed LPS from their cell envelopes. Shed LPS aggregates are recognized by LPS binding proteins and receptors, which activate the host's immune system. Uncontrolled and excessive stimulation of the host's immune system precipitates endotoxic shock which in advanced cases involving multiple system organ failure inevitably lead to patient's death. Many strategies have been tested out to combat this deadly affliction. One of the attractive clinical modalities in sepsis treatment is the use of peptides as LPS sequestering anti-endotoxic drugs. A classical peptide antibiotic of this class is Polymyxin B (PMB) a cyclic cationic acylated molecule, that recognizes LPS with a very high affinity. This thesis describes kinetics and thermodynamics of PMB-LPS interactions and applies these parameters over a framework of different models so as to gain insights into the structure-function relationships that govern the interactions of this peptide with endotoxin(s). Classical biophysical techniques like fluorescence, circular dichroism spectroscopy, stopped flow kinetics, titration calorirnetry (ITC) and the relatively new technique of Surface Plasmon Resonance (SPR) have been employed to dissect out the mechanism of the range of non-covalent forces that are involved in peptide-endotoxin recognition. Certain proteins that exhibit LPS binding activity have also been studied to gains insight about their mode of action. Implications of these studies for designing peptides that have better anti-endotoxic properties are also highlighted. The first chapter introduces and highlights the clinical features of sepsis. It also attempts to shed light on the LPS mediated signal transduction pathway that leads to endotoxic shock. This chapter also briefly explains the roles of many LPS receptors that are present in the human system and their specific roles in the signal transduction pathways. The second part of this chapter deals with the role of cationic peptides as anti-endotoxic drugs. Certain key functional aspects of these peptides, which impart in them, the desirable property of LPS recognition have also been discussed The second chapter describes the kinetic studies undertaken to unravel the exact mechanism of LPS-PMB interaction. The studies reveal that PMB recognizes LPS in a biphasic manner, with the second, unimolecular isomerization step of the reaction being the rate-limiting step. The initial reaction is shown to be influenced by the presence of salt in the reaction medium. The dissociation phase of this interaction also shows a biphasic pattern. These data allow us to speculate upon the exact mechanism by which PMB is able to recognize LPS. The studies also shed light on some structural aspects that govern and confer such high LPS binding activity to PMB. Based on these a model has been proposed to explain this recognition (C.J. Thomas et al, 1998). The second chapter discuses the mode of action of various PMB analogs. These analogs have been chosen in terms of their mode of action as well as their structural similarly to PMB. The affinities of these analogs to LPS and lipid A were quantified using the Surface plasmon resonance (SPR) method. SPR, a technique that relies on the quantification of change in mass during a binary binding process occurring between an immobilized entity and a flowing ligand, is a rapid and sensitive method to measure biologically relevant interactions. SPR studies provide us with the binding constants and thermodynamic parameters that allow evaluation of the affinities of these peptides towards LPS (C.J.Thomas and A.Surolia, 1999). The third chapter discusses a hitherto unknown mode by which PMB acts on a LPS lamellae. The results of this study wherein the binding affinities of PMB and its analogs were performed on monolayers and tethered liposomes, show that PMB is able to remove specifically LPS or lipid A from monolayers or bilayer assemblies such as tethered liposomes. The exact mode of action of PMB is deciphered in the light of these new studies, which allow us to posit on the observed efficacy of PMB in neutralizing the endotoxin as compared to peptides with nearly similar affinities for LPS (C.J Thomas et al 1999). In the fourth chapter a series of 23 residue peptides, based on the sequence corresponding to the anti-sense strand of magainin gene have been synthesized. Magainin an amphiphilic helical peptide obtained from frog skins plays a vital role in the innate immune defense mechanisms of these organisms. It also exhibits LPS binding activity that makes it an attractive target as an anti-endotoxic drug. Biochemical and biophysical characterization of these peptides reveal that they have the tendency to perturb both the inner and the outer membranes of E.coli. The peptides are amphiphilic and have helical structure in a membrane bound environment. Three of the peptides tested have high affinities for lipid A that approach the values shown by PMB. The kinetic parameters obtained by stopped flow and SPR studies in conjunction with the therrnodynamic parameters obtained using ITC studies allow us to highlight the key structural features that need to be exhibited by peptides that are designed to be LPS recognizers. The studies also project the fact that ionic forces play an important role in the initial recognition of LPS by these peptides. Fortification of the might of these ionic charges increases affinity for LPS where as the hydrophobic residues that interact at the next phase of binding are more amenable to disruptions in contiguity. These factors are discussed using the helical wheel diagram that shows the clear amphiphilicity displayed by these peptides. (C.J Thomas et al Manuscript under preparation, 2000) Chapter six discusses the mode of action of certain LPS binding proteins. Limulus anti endotoxic factor (LALF) plays a vital role in the innate immune based defense systems of the horseshoe crab. Galectin-3 is a metal ion independent, galactosc binding Icctin of human origin with unknown functions. Both these phylogcntically-unrclatcd proteins exhibit LPS/lipid A recognizing properties. ITC and SPR studies have been used to determine the binding constants displayed by these proteins for lipid A. LALF bind to lipid A with very high affinity than compared to Galectin-3 and is also able to take away selectively lipid A from both monolayers and tethered liposomes. Galectin-3 does not show this property of LALF, which might account for its lowered affinities. Also structurally LALF has amphiphilic nature that confers high lipid A binding activity, which is clearly lacking in Galectin-3. These studies in conjunction with the knowledge gained from the study of LPS-PMB interaction stress on the importance of amphiphilicity in LPS recognition. (C.J Thomas et al Manuscript under preparation, 2000). The final chapter is a general discussion that attempts to collate all these kinetic and thermodynamic observations in the pursuit of designing small easily manipulatable peptides that exhibit high LPS binding activity. These studies are aimed to act as rough guidelines to the design of LPS sequestering peptides that might have better therapeutic and pharmacokinetic properties. The appendix to the main body of work presented in thesis are two pieces of work pertaining to the elucidation the kinetics and mechanism of sugar lectin interactions, when sugars are presented as glycolipids in monolayers or bilaycrs liposomes. Mode of the presentation of sugars at cell-surfaces in the form of glycolipids as ligands influence their recognition by macromolecular receptors like lectins. Appendix 1 is a study of the mode of action of Ulex europeus I lectin binding to H-fucolipid containing tethered liposomes, by SPR. Fucosylated sugars are often used as key markers in histochemical analysis of malignant cancerous tissues. Ulex lectin plays a vital role as a marker for identification of these tissues. The kinetics and thermodynamic parameters that are obtained in this study throw some light on the mode of recognition of glycolipid receptor by Ulex europeus I lectin (C.J Thomas and A. Surolia 2000). Appendix 2 is a study, that attempts to quantify the initial kinetic parameters that correlate the recognition of glycolipid receptors with their inclination at the membrane surface and the influence of charge on them by soyabean agglutinin (SBA), Abrus agglutinin I and II. Studies on the soyabean agglutinin-globoside interaction highlights the divalent cation mediated reorientation of these receptors on their accessibility and recognition to the agglutinin. The divalent cations are speculated to orient the oligosaccharide head groups in a spatial geometry that allows a heightened kinetics of their interaction by SBA. These studies reveal that the reorganization of the binding pocket of a lectin can also have a profound influence on ihc rates of recognition of a glycospingolipid ligand by a lectin as exemplified by Abrus agglutinin II- GM1 interactions (C.J Thomas ct al, Manuscript under preparation).

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Kobayashi, Cláudia Castelo Branco Artiaga. "Fenótipos de β-lactamases e fatores de risco associados com klebsiella pneumoniae produtora de carbapenemase em um hospital de referência estadual em urgência e emergência de Goiânia, Goiás." Universidade Federal de Goiás, 2013. http://repositorio.bc.ufg.br/tede/handle/tede/8618.

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Carbapenemase-producing Klebsiella pneumoniae is an enterobacteria, commonly associated with resistance to multiple antibiotics. The presence of multidrug resistance phenotype is an important challenge in the epidemiological point of view, regarding the therapeutic management and infection control. A retrospective observational study was conducted in a tertiary-care hospital in Goiânia, Brazil, in the period of 2006 to 2011 to investigate the carbapenemases phenotypes, the in vitro activity of tigecycline and polymyxin B and determine the risk factors associated with infection or colonization by carbapenemase-producing K. pneumoniae. The serine-carbapenemase production was detected by modified Hodge test and combined disk test with boronic acid; metallo-β-lactamases - MβL by double-disk synergy test with imipenem and EDTA; extended spectrum β-lactamases - ESBL by combined disk with cefotaxime and ceftazidime with and without clavulanate, and plasmid AmpC type by combined disk with boronic acid and cefoxitin. The in vitro activity of tigecycline and polymyxin B against the enzyme-producing isolates was assessed using the broth microdilution method and for not β-lactam antimicrobials by disk diffusion and semi-automated system. The association between independent risk factors and colonization or infection by carbapenemase-producing K. pneumoniae was determined by logistic regression analysis. The carbapenem resistance was found in 8.06% of all isolates K. pneumoniae and 6.90% were carbapenemase producers. Among carbapenemases producers isolates, 77.78% were KPC type β-lactamase, 37.04% demonstrated the simultaneous production of plasmid AmpC β-lactamase and KPC, 29.63% associated with MβL or ESBL and KPC, 11.11% MβL/ESBL/KPC and 7.41% MβL/ESBL/KPC/plasmid AmpC. High percentages of not β-lactams antimicrobial resistance were observed, ranging from 61.10% - 74.70% to fluoroquinolones and 52.10% - 54.30% to aminoglycosides. Polymyxin B showed limited activity against the carbapenemase-producing K. pneumoniae (35.70%) and tigecycline was the only antimicrobial that inhibited 75.0% of these multidrug-resistant strains. The independent risk factors for K. pneumoniae carbapenemase producers were prolonged hospitalization (p = 0.031), previous use of carbapenems (p = 0.041) and exposure to more than three antimicrobials (p = 0.034). The detection of multidrug- resistant carbapenemase-producing isolates and the knowledge of different resistance mechanisms can result in significant impact on the treatment outcomes and strategies for infection control and prevention.
Klebsiella pneumoniae produtora de carbapenemase é uma enterobactéria, comumente associada à resistência aos múltiplos antimicrobianos. A presença deste fenótipo de multirresistência consiste em um importante desafio do ponto de vista epidemiológico, quanto ao manejo terapêutico e ao controle de infecção. Um estudo observacional retrospectivo foi conduzido em um hospital público terciário em Goiânia, Go, Brasil, no período entre 2006 e 2011, para investigar os fenótipos de carbapenemases, a atividade in vitro da tigeciclina e polimixina B e determinar os fatores de risco associados à infecção ou colonização por K. pneumoniae produtora de carbapenemase. A presença de serina carbapenemase foi detectada por meio do teste de Hodge modificado e disco combinado com ácido borônico; metalo-β-lactamases – MβL por sinergismo de disco duplo com imipenem e EDTA; β-lactamases de espectro estendido – ESBL, através do disco combinado com cefotaxima e ceftazidima com e sem ácido clavulânico e AmpC plasmidial por disco combinado com ácido borônico e cefoxitina. A atividade in vitro da tigeciclina e polimixina B foi avaliada através do método de microdiluição em caldo e dos antimicrobianos não β-lactâmicos por disco-difusão e sistema semiautomatizado. A associação entre fatores de risco independentes e colonização ou infecção foi determinada através de regressão logística. A resistência aos carbapenêmicos foi verificada em 8,06% do total de K. pneumoniae e a atividade de carbapenemase em 6,90%. Dentre os isolados produtores de carbapenemases, 77,78% foram considerados β-lactamase tipo KPC, 37,04% demonstraram a produção simultânea de AmpC plasmidial e KPC, 29,63% associação com MβL ou ESBL e KPC, 11,11% MβL/ESBL/KPC e 7,41% MβL/ESBL/KPC/AmpC plasmidial. Altas taxas de resistência aos antimicrobianos não β-lactâmicos foram observadas, variando de 61,10% - 74,70% para fluoroquinolonas e 52,10% - 54,30% para aminoglicosídeos. A polimixina B apresentou baixa atividade in vitro contra estes isolados (35,70%) e a tigeciclina foi o único antimicrobiano que inibiu 75,0% dos mesmos. Os fatores de risco independentes para K. pneumoniae produtora de carbapenemase foram a internação prévia prolongada (p = 0,031), uso prévio de carbapenêmicos (p = 0,041) e exposição a mais de três antimicrobianos (p = 0,034). A detecção de isolados produtores de carbapenemase multirresistentes e o conhecimento dos diferentes mecanismos de resistência podem resultar em significante impacto nos resultados terapêuticos e estratégias de controle de infecção e prevenção.

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45

Dixon, R. A. "Effects of polymyxins on the cell envelope of Escherichia coli." Thesis, University of Bristol, 1986. http://hdl.handle.net/1983/c8c95b95-75e9-48c7-91d6-42e0d60f5880.

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Luerce, Rogério de Faria. "Produção de acetoína por Bacillus polymyxa." Florianópolis, SC, 2002. http://repositorio.ufsc.br/xmlui/handle/123456789/84379.

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Química
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A produção do bioaroma acetoína pela bactéria Bacillus polymyxa CCT 2479 utilizando glicose como fonte de carbono em condições aeróbias foi estudada. Primeiramente, foram realizados ensaios em frascos agitados em meio PAY para verificar algumas características de crescimento e produção de acetoína. Numa segunda etapa, desenvolveu-se um planejamento fatorial completo em dois níveis (concentração inicial de glicose em 30 e 50 g/L e pH 5,5 e 6,5) adicionado de ponto central (concentração inicial de glicose em 40 g/L e pH 6,0) para avaliar a influência da concentração inicial de substrato e do pH sobre a produção de acetoína nos ensaios em biorreator. Os efeitos principais do pH e concentração inicial de substrato mostraram-se significativos no modelo proposto para a concentração máxima em acetoína. A concentração máxima de acetoína (7,97 g/L) foi obtida no ensaio conduzido em pH 5,5 e concentração inicial de glicose de 50 g/L. Os resultados observados indicaram que a produção de acetoína esteve associada ao crescimento celular nos ensaios em biorreator.

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Noguès, Aurélie. "Résistance adaptative aux polymyxines chez Pseudomonas aeruginosa." Thesis, Besançon, 2015. http://www.theses.fr/2015BESA3006.

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La résistance aux polymyxines chez P. aeruginosa résulte en partie de la modification du lipide A par addition de 4-amino-aL-arabinose (L-Ara4N), due à l'expression de l'opéron arnBCADTEF-ugD (arn), activée par au moins 6 systèmes de régulation à deux composants (S2C). Nous avons mis en évidence que P. aeruginosa était capable de s'adapter de manière transitoire à la présence de fortes concentrations de polymyxines (8 x CMI) aussi bien in vitro que in vivo dans un modèle murin d'infection pulmonaire aiguë. La délétion de l'opéron arn chez la souche sauvage n'a pas modifié la capacité d'adaptation de P. aeruginosa. Afin d'identifier les gènes impliqués dans le processus adaptatif, le transcriptome global du mutant PAOl/z«;-Aar«-ATCS délété des principaux S2C (parRS, pmrAB, cprRS eiphoPQ) et de l'opéron arn a été réalisé en présence de différentes concentrations de colistine par RNA-Seq. Deux nouveaux mécanismes ont ainsi été identifiés. L'un repose sur l'expression de l'opéron mmsAB codant des enzymes du catabolisme des acides gras et l'autre fait intervenir le facteur sigma alternatif AlgU. Seule la délétion conjointe du gène algW participant à l'activation de AlgU et des opérons arn, mmsAB, pmrAB, parRS, phoPQ et cprRS a permis d'abolir complètement la résistance adaptative à la colistine. Par ailleurs, nous avons mis en évidence le rôle des vésicules de membrane externe (OMVs) dans la séquestration de l'antibiotique, dont la production semble régulée au moins par AlgU et le PQS. Ces travaux offrent des perspectives intéressantes pour l'identification de nouvelles cibles antibactériennes et pour l'amélioration de l'effet bactéricide des polymyxines
Resistance to polymyxins in Pseudomonas aeruginosa involves the addition of 4-amino-L-arabinose (Ara4N) to LPS phosphates, thanks to an enzymatic modification due to the operon named arnBCADTEF-ugD (arn) whose expression is activated by at least 6 two component regulatory Systems (TCS). We demonstrated that P. aeruginosa was able to resist in a transient way to high concentrations of polymyxins (8x MIC) in vitro and in vivo in a mice lung infection model. Arn operon deletion in the wild type strain did not modify the ability to adapt to polymyxins. In order to identify gènes involved in adaptive resistance, we performed RNA-seq transcriptomes of quintuple mutant PAO\lux-Aaw-ATCS exposed to different concentrations of colistin or non exposed. Two new mechanisms were identified. The first one is based upon mmsAB operon encoding fatty acid catabolism enzymes and the second one is due to the sigma factor AlgU. Only the deletions of algW%enz involved in AlgU activation and arn, mmsAB, pmrAB, parRS, phoPQ and cprRS operons completely abolished the adaptive process. We also demonstrated the role of outer membrane vesicles in the sequestration of colistin whose production is regulated by AlgU and PQS. This study provides knoweldge essential for the design of novel strategies aimed at tackling the adaptive resistance to polymyxins

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McAllister, Stephen M. "Liposomes as carriers for polymyxins in the treatment of cystic fibrosis lung infections." Thesis, Aston University, 1995. http://publications.aston.ac.uk/11044/.

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Cystic fibrosis (CF) is the most common autosomal recessive disorder affecting Caucasian populations. The pathophysiology of this disorder predisposes the lungs of affected patients to chronic infection, typically by Pseudomonas aeruginosa, which is the main cause of morbidity and mortality. Recently, attention has focused on aerosolised polymyxins, which are given prophylactically in an effort to limit infection and subsequent lung damage. This class of antimicrobial compounds is highly active against P. aeruginosa and possess the advantage that resistance rarely develops. However, the rapid lung clearance of antibiotics is a well documented phenomenon and it was postulated that polymyxin treatment could be further improved by liposomal encapsulation. As part of the development of liposomal polymyxin B, analytical methodology (radiolabelling, HPLC and protein assay) applicable to liposomal formulations was established. Liposomes were prepared by the dehydration-rehydration method and encapsulation efficiencies were determined for a number of phospholipid compositions. Vesicles were characterised with respect to size, zeta potential, morphology and release characteristics. The surface hydrophobicity of vesicles was quantified by hydrophobic interaction chromatography and it was found that this method produced comparable results to techniques conventionally used to assess this property. In vivo testing of liposomal polymyxins demonstrated that encapsulation successfully prevented the rapid pulmonary clearance of PXB. Antimicrobial activity of liposomal formulations was quantified and found to be dependent on both the vesicle surface characteristics and their release profile. Investigation of the interaction of PXB with lipopolysaccharide was undertaken and results demonstrated that PXB caused significant structural distortion of the lipid A region. This may be sufficient to abrogate the potentiating action of LPS in the inflammatory cascade.

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Barr, Kathryn J. "Aspects of the host-parasite relationships of Polymyxa betae." Thesis, University of East Anglia, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334265.

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Mariotto, Juliana Ribeiro. "Produção de acetoína e 2,3-butanodiol por Bacillus polymyxa." Florianópolis, SC, 2007. http://repositorio.ufsc.br/xmlui/handle/123456789/90255.

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Química
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O presente trabalho tem como objetivo estudar a influência da fonte de nitrogênio, pH e transferência de oxigênio no crescimento da bactéria Bacillus polymyxa, consumo de substrato e formação dos aromas acetoína e 2,3-butanodiol. Estas substâncias são responsáveis pelo aroma de produtos lácticos, além de atuarem como potencializadores de outros aromas. Os cultivos foram realizados em três etapas diferentes, utilizando o meio de cultura Phosphate Ammonium Yeast (PAY) e glicose como fonte de carbono. Na primeira etapa, desenvolvida em frascos aletados, utilizou-se três diferentes fontes de nitrogênio, extrato de levedura, sulfato de amônio e uréia, sendo que a proporção deste componente no meio de cultura foi a mesma para os todos os ensaios realizados. Na segunda etapa, também em frascos aletados, o volume do meio de cultura (400, 500 e 600 mL) e o pH (4,5, 5,5 e 6,5) foram modificados, realizando o controle deste último parâmetro durante todo o cultivo, ou somente ajustando-o no início do processo. E a terceira etapa foi executada em biorreator de 4L, visando uma ampliação de escala. A concentração celular foi determinada associando dois métodos diferentes, a turbidimetria e a gravimetria. A glicose foi quantificada utilizando o kit glicose-PP (Gold Analisa) e a concentração dos aromas foi determinada através da cromatografia gasosa. Os resultados obtidos nos ensaios realizados em frascos agitados mostraram que o extrato de levedura é a melhor fonte de nitrogênio, obtendo-se 9,8 g/L de concentração celular, 24,2 g/L de 2,3-butanodiol e 15,0 g/L de acetoína, além de concentrações residuais de glicose muito próximas de zero. Este ensaio também apresentou os melhores resultados na segunda etapa de experimentos, onde se estudou a influência do pH e da transferência de oxigênio, sendo este último avaliado através da modificação do volume do meio de cultura. As condições de cultivo utilizadas neste ensaio foram pH inicial de 6,5 e volume de meio de cultura de 400 mL. Com o controle do pH, resultados semelhantes de biomassa e produtos foram obtidos, 9,8 g/L de células, 19,9 g/L de 2,3-butanodiol e 13,7 g/L de acetoína, mostrando que o controle deste parâmetro não afeta significativamente a formação dos aromas. No entanto, maiores velocidades de crescimento foram obtidas com o controle dos diferentes pHs estudados, além de favorecer o consumo da glicose. O ensaio realizado em biorreator mostrou que a aeração contínua prejudica a formação dos produtos, atingindo concentrações de 3,5 g/L de 2,3-butanodiol e 4,3 g/L de acetoína. Elevada produção de células foi alcançada, 7,6 g/L, indicando que o oxigênio favorece o crescimento do microrganismo no início do cultivo. A partir de um determinado período do processo, este componente não deve ser desejado, pois a formação dos produtos ocorre por processo fermentativo, e a presença deste afeta consideravelmente a concentração final dos aromas. This work aims to study the influence of the source of nitrogen, pH and the transfer of oxygen on the growth of the bacterium Bacillus polymyxa, consumption of substrate and production of the aromas acetoin and 2,3-butanediol. These substances are responsible for the aroma of lactic products, and serve as power of other flavorings. The fermentations have been conducted in three different stages, using the means of culture Yeast Ammonium Phosphate (PAY), and glucose as a source of carbon. In the first step, developed in erlenmeyers flasks with baffles is used for yeast extract, ammonium sulphate and urea as a source of nitrogen, and the proportion of this component in the means of culture was the same for all tests. In the second stage, also in erlenmeyers flasks with baffles, the volume of the means of culture (400, 500 and 600 mL) and pH (4.5, 5.5 and 6.5) were modified, making the control of the latter parameter throughout the fermentation, or only adjusted at the beginning of the process. And the third stage was performed at bioreactor of 4L, seeking an ampliation of scale. The cellular concentration was determined linking two different methods, turbidimetry and gravimetry. The glucose was measured using the kit glucose-PP (Gold Analisa) and the aromas concentrations were determined by gas chromatography. The results achieved in the flasks with baffles showed that the yeast extract is the best source of nitrogen, attaining 9.8 g/L of cellular concentration, 24.2 g/L of 2,3-butanediol and 15.0 g/L of acetoin, besides residual concentrations of glucose very close to zero. This test also showed the best results in the second stage of experiments, where were the influence of pH and the transfer of oxygen studied, the latter being evaluated by the volume change of the means of culture. The conditions of cultivation used were initial pH of 6.5 and volume of means of cultivation of 400 mL. With the control of pH, similar results were obtained, 9.8 g/L of cells, 19.9 g/L of 2,3-butanediol and 13.7 g/L of acetoin, showing that the control of this parameter does not affect significantly the formation of the products. However, higher rates were obtained with the control of different pHs studied, and encourage the consumption of glucose. The test performed in bioreactor showed that the continuous aeration affects the formation of the products, reaching concentrations of 3.5 g/L of 2,3-butanediol and 4.3 g/L of acetoin. High production of cells was achieved, 7.6 g/L, indicating that the oxygen promotes the growth of microorganism early in the cultivation. From a certain period of the process, this component should not be desired, since the formation of the products occurs by process fermentative, and the presence of this affects considerably the final concentration of aromas.

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Dissertations / Theses on the topic 'Polymyxin E'

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