Academic literature on the topic 'Carbapenemase gram negative bacteria'
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Journal articles on the topic "Carbapenemase gram negative bacteria"
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Asthana, Sonal, Purva Mathur, and Vibhor Tak. "Detection of Carbapenemase Production in Gram-negative Bacteria." Journal of Laboratory Physicians 6, no. 02 (2014): 069–75. http://dx.doi.org/10.4103/0974-2727.141497.
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ABSTRACTThe greatest threat to antimicrobial treatment of infections caused by Gram-negative bacteria is the production of carbapenemases. Metallo-beta-lactamases and plasmid-mediated serine carbepenemases like Klebsiella pneumonia carbapenemase are threatening the utility of almost all currently available beta-lactams including carbapenems. Detection of organisms producing carbapenemases can be difficult, because their presence does not always produce a resistant phenotype on conventional disc diffusion or automated susceptibility testing methods. These enzymes are often associated with laboratory reports of false susceptibility to carbapenems which can be potentially fatal. Moreover, most laboratories do not attempt to detect carbapenemases. This may be due to the lack of availability of guidelines and procedures or lack of knowledge and expertise. Because routine susceptibility tests may be unreliable, special tests are required to detect the resistance mechanisms involved. This document describes the standard methodology for detection of various types of carbapenemases, which can be put to use by laboratories working on antimicrobial resistance in Gram-negative bacteria.
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Hammoudi Halat, Dalal, and Carole Ayoub Moubareck. "The Current Burden of Carbapenemases: Review of Significant Properties and Dissemination among Gram-Negative Bacteria." Antibiotics 9, no. 4 (2020): 186. http://dx.doi.org/10.3390/antibiotics9040186.
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Carbapenemases are β-lactamases belonging to different Ambler classes (A, B, D) and can be encoded by both chromosomal and plasmid-mediated genes. These enzymes represent the most potent β-lactamases, which hydrolyze a broad variety of β-lactams, including carbapenems, cephalosporins, penicillin, and aztreonam. The major issues associated with carbapenemase production are clinical due to compromising the activity of the last resort antibiotics used for treating serious infections, and epidemiological due to their dissemination into various bacteria across almost all geographic regions. Carbapenemase-producing Enterobacteriaceae have received more attention upon their first report in the early 1990s. Currently, there is increased awareness of the impact of nonfermenting bacteria, such as Acinetobacter baumannii and Pseudomonas aeruginosa, as well as other Gram-negative bacteria that are carbapenemase-producers. Outside the scope of clinical importance, carbapenemases are also detected in bacteria from environmental and zoonotic niches, which raises greater concerns over their prevalence, and the need for public health measures to control consequences of their propagation. The aims of the current review are to define and categorize the different families of carbapenemases, and to overview the main lines of their spread across different bacterial groups.
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Ageevets, V. A., O. S. Sulian, A. A. Avdeeva та ін. "Comparative Activity of Carbapenem Antibiotics Against Gram-Negative Carbapenemase Producers of Different Groups". Antibiotics and Chemotherapy 67, № 1-2 (2022): 9–15. http://dx.doi.org/10.37489/0235-2990-2022-67-1-2-9-15.
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The rapid spread of gram-negative bacteria resistance to carbapenems due to the production of carbapenemases requires new treatment options. The activity of carbapenem antibiotic biapenem, recently registered in Russia, against producers of various carbapenemases was studied in comparison with other antibiotics of this group. Among NDM-type carbapenemase producers, 77.8% demonstrated clinical susceptibility to biapenem; 50.3% and 21.1% of isolates were susceptible to meropenem and imipenem, respectively. Among the producers of OXA-48-type carbapenemases, 82,6%, 60,9%, and 65,2% of isolates demonstrated susceptibility to biapenem, imipenem, and meropenem, respectively.Producers of KPC-type carbapenemases were 100% resistant to all carbapenems. The introduction of biapenem will significantly expand the possibilities of treating severe infections caused by carbapenemase producers.
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Das, Parijat, Kumar Anand Shrutiraaj, Manish Ranjan, and Sourav Sen. "Prevalence of Carbapenem Resistance and their Genotypic Profile among Gram-Negative Bacteria in a Tertiary Care Hospital in Western India." Annals of Pathology and Laboratory Medicine 8, no. 5 (2021): A116–123. http://dx.doi.org/10.21276/apalm.3053.
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Background: Resistance to carbapenems due to carbapenemases has been increasingly noticed worldwide. Detection of carbapenemases among Gram‑negative bacteria (GNB) is important for
 both clinicians and infection control practitioners. Both phenotypic and molecular methods can be used for detection of Carbapenemases production. Molecular methods although the gold standard for detection of carbapenemases are not used routinely as they might not be immediately available coupled with expertise required, cost and infrastructure incurred and limited by the number of targets detected.
 Methods: Consecutive non-repeat gram negative isolates isolated from various clinical specimens from intensive care unit (ICU) were included in the study. Antimicrobial susceptibility testing was done on Mueller Hinton’s agar by Kirby Bauer Disc diffusion method as per the Clinical and Laboratory Standards Institute (CLSI) guidelines. Isolates resistant to Meropenem were further screened for carbapenemase producing genes using multiplex polymerase chain reaction (PCR). The results were statistically analysed.
 Result: A total of 350 gram negative bacteria were screened for carbapenem resistance. Carbapenem resistance was found in 109 GNB. The metallo‑ β‑lactamases were most common carbapenemases followed by KPC.
 Conclusion: Carbapenemase producing bacteria are a major threat of the 21st century. Preventing emergence and spread of these pathogens through strict infection control practices, judicious use of antibiotics and early and timely detection will contribute in preserving carbapenems, the last resort antibiotics.
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Karn, Sitesh, Narayan Dutt Pant, Sanjeev Neupane, Saroj Khatiwada, Shaila Basnyat, and Basudha Shrestha. "Prevalence of carbapenem resistant bacterial strains isolated from different clinical samples: study from a tertiary care hospital in Kathmandu, Nepal." Journal of Biomedical Sciences 3, no. 1 (2017): 11–15. http://dx.doi.org/10.3126/jbs.v3i1.16846.
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Background Carbapenems are considered as drugs of choice for the treatment of the infections caused by drug resistant bacteria. However, in the recent years the prevalence of carbapenem resistant gram negative bacteria has increased significantly. The main objective of this study was to determine the prevalence of carbapenemase producing gram negative bacteria among all the clinical isolates.Material and methods A total of 3246 non-repeated, different clinical specimens from patients attending Kathmandu Model Hospital, from July 2013 to January 2014 were cultured and the gram negative bacterial isolates obtained were subjected to identification with the help of colony morphology, Gram’s stain and conventional biochemical tests. Kirby-Bauer disk diffusion technique was used to perform antimicrobial susceptibility testing. Phenotypic confirmation of carbapenemase and AmpC beta-lactamase production was done by combined disc method.Results 890 samples showed the growth of bacterial pathogens. Out of total 769 gram negative bacteria, 57 were found to be carbapenem resistant. Of which, highest number (47) of the isolates were found to be metallo-β lactamase (MBL) producers. Six bacterial isolates produced both (Klebsiella pneumoniae carbapenemase) KPC and MBL, whereas only one isolate was found to be positive for both MBL and AmpC. Three bacterial strains showed carbapenem resistance due to over production of AmpC β-lactamase.Conclusion Among carbapenem resistant gram negative bacteria, MBL was present as the major enzyme responsible for resisting carbapenem antibiotics.
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Montiel-Riquelme, Francisco, Elisabeth Calatrava-Hernández, Miguel Gutiérrez-Soto, Manuela Expósito-Ruiz, José María Navarro-Marí, and José Gutiérrez-Fernández. "Clinical Relevance of Antibiotic Susceptibility Profiles for Screening Gram-negative Microorganisms Resistant to Beta-Lactam Antibiotics." Microorganisms 8, no. 10 (2020): 1555. http://dx.doi.org/10.3390/microorganisms8101555.
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The increasing resistance to antibiotics is compromising the empirical treatment of infections caused by resistant bacteria. Rapid, efficient, and clinically applicable phenotypic methods are needed for their detection. This study examines the phenotypic behavior of β-lactam-resistant Gram-negative bacteria grown on ChromID ESBL medium with ertapenem, cefoxitin, and cefepime disks, reports on the coloration of colonies, and establishes a halo diameter breakpoint for the detection of carbapenemase-producing bacteria. We studied 186 β-lactam-resistant Gram-negative microorganisms (77 with extended spectrum beta lactamase (ESBL), 97 with carbapenemases, and 12 with AmpC β-lactamases (AmpC)). Susceptibility profiles of Gram-negative bacteria that produced ESBL, AmpC, and carbapenemases were similar to the expected profiles, with some differences in the response to cefepime of ESBL-producing microorganisms. Coloration values did not differ from those described by the manufacturer of ChromID ESBL medium. In the screening of carbapenemase production, inhibition halo diameter breakpoints for antibiotic resistance were 18 mm for Enterobacterales and ertapenem, 18 mm for Pseudomonas and cefepime, and 16 mm for Acinetobacter baumannii and cefepime. This innovative phenotypic approach is highly relevant to clinical laboratories, combining susceptibility profiles with detection by coloration of high-priority resistant microorganisms such as carbapenemase-producing A. baumannii, carbapenemase-producing Pseudomonas spp., and ESBL and/or carbapenemase-producing Enterobacterales.
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Bogiel, Tomasz, Mateusz Rzepka, and Eugenia Gospodarek-Komkowska. "An Application of Imipenem Discs or P. aeruginosa ATCC 27853 Reference Strain Increases Sensitivity of Carbapenem Inactivation Method for Non-Fermenting Gram-Negative Bacteria." Antibiotics 10, no. 7 (2021): 875. http://dx.doi.org/10.3390/antibiotics10070875.
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Non-fermenting Gram-negative rods are one of the most commonly isolated bacteria from human infections. These microorganisms are typically opportunistic pathogens that pose a serious threat to public health due to possibility of transmission in the human population. Resistance to beta-lactams, due to carbapenemases synthesis, is one of the most important antimicrobial resistance mechanisms amongst them. The aim of this study was to evaluate the usefulness of the Carbapenem Inactivation Method (CIM), and its modifications, for the detection of carbapenemase activity amongst non-fermenting Gram-negative rods. This research involved 81 strains of Gram-negative rods. Of the tested strains, 55 (67.9%) synthesized carbapenemases. For non-fermenting rods, 100% sensitivity and specificity was obtained in the version of the CIM test using imipenem discs and E. coli ATCC 25922 strain. The CIM test allows for differentiation of carbapenems resistance mechanisms resulting from carbapenemase synthesis from other resistance types. It is a reliable diagnostic method for the detection of carbapenemase activity amongst non-fermenting Gram-negative rods. Application of imipenem discs and P. aeruginosa ATCC 27853 reference strain increases CIM results sensitivity, while imipenem discs and E. coli ATCC 25922 strain use maintains full precision of the test for non-fermenting rods.
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Ibadin, Ephraim E., Angela Eghiomon, Nosakhare L. Idemudia, et al. "Phenotypic Distribution of Serine- and Zinc-Type Carbapenemases Among Clinical Bacterial Isolates in a Tertiary Hospital in Benin, Nigeria." International Journal of Enteric Pathogens 8, no. 1 (2020): 3–7. http://dx.doi.org/10.34172/ijep.2020.02.
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Background: Serine and zinc type carbapenemases are distributed in many genera of bacteria and are typically associated with specific regions or countries. Objectives: This study phenotypically determined the prevalence of serine and zinc-type carbapenemases among Gram-negative bacilli recovered from clinical specimens in Benin, Nigeria. Materials and Methods: Totally, 158 consecutive non-duplicate bacterial isolates (gram-negative bacilli) recovered from clinical samples were screened for serine and zinc-type carbapenemases using the simplified carbapenemase inactivation (sCIM) and ethylenediaminetetraacetic acid -double-disc synergy test methods. Results: The isolates recovered from clinical specimens included 126 Enterobacteriaceae (79.7%), 7 Acinetobacter spp (3.7%), and 28oxidase positive gram negative bacilli (17.7%). Twenty-eight isolates (17.7%) out of the 158 tested samples were carbapenemase positive. There was no significant difference in the prevalence of serine- and zinc-type carbapenemases (P=0.0748). However, the prevalence of zinc-type carbapenemase was significantly higher in Pseudomonas aeruginosa compared with other isolates (P=0.0028) while that of serinetype carbapenemase was not affected by the type of clinical isolates (P=0.7216). Finally, the prevalence of both serine- and zinc-type carbapenemases were not affected (P>0.05) by clinical specimens and the source of isolates (in-patient vs. out-patient) respectively. Conclusion: In general, the prevalence of zinc-type (12%) carbapenemases was insignificantly higher than that of serine-type (5.7%) carbapenemases. The measures to reduce infections caused by carbapenemase-producing organisms (CPOs) are advocated accordingly.
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Huynh, Tuan, and Loan Luong. "SG-APSIC1083: Prevalence and classification of carbapenemase-producing gram-negative bacilli at a medical center in Ho Chi Minh City, Vietnam." Antimicrobial Stewardship & Healthcare Epidemiology 3, S1 (2023): s27. http://dx.doi.org/10.1017/ash.2023.81.
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Objectives: The identification and classification of carbapenemases are meaningful in clinical treatment, epidemiology, and multidrug-resistant bacteria control. We sought to identify the proportion of carbapenemase-producing and carbapenemase classifications in gram-negative bacilli in our hospital. Methods: Isolates of gram-negative bacilli were extracted from sputum, blood, and urine samples in a medical center in Ho Chi Minh City. The identification of gram-negative bacilli was performed using the Phoenix M50 automated system (Becton Dickinson, Franklin Lakes, NJ). An antibiogram was conducted using the disk-diffusion method to detect meropenem-resistant gram-negative bacteria. Carbapenemase confirmation and classification of isolates resistant or intermediately resistant to meropenem were performed using the NMIC500 CPO kit on the Phoenix M50 system. Results: Among 599 isolates of gram-negative bacilli, 108 isolates were resistant or intermediately resistant to carbapenem (meropenem). Of these108 isolates, 107 (99.1%) were resistant due to the carbapenemase-producing mechanism. The proportions of resistant or intermediately resistant isolates to carbapenem were as follows: 73.8% for Acinetobacter baumannii, 26.4% for Klebsiella pneumoniae, 25.9% for Pseudomonas aeruginosa, and 2.8% for Escherichia coli. Class D carbapenemase accounted for the highest proportion, with 53 (49.5%) of 107 isolates, followed by class B with 31 isolates (29%), and class A with the lowest proportion of 2 isolates (1.9%). Also, 44.4% of Acinetobacter baumannii isolates and 74.4% of Klebsiella pneumoniae isolates produced class D carbapenemase. Conclusions: Gram-negative bacilli are resistant to carbapenem primarily due to the carbapenemase-secreting mechanism. D-class carbapenemase accounted for the highest percentage, followed by B-class type, and A-class carbapenemase in gram-negative bacilli.
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Ragueh, Ayan Ali, Mohamed Houmed Aboubaker, Sitani Idriss Mohamed, Jean-Marc Rolain, and Seydina M. Diene. "Emergence of Carbapenem-Resistant Gram-Negative Isolates in Hospital Settings in Djibouti." Antibiotics 12, no. 7 (2023): 1132. http://dx.doi.org/10.3390/antibiotics12071132.
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Introduction: The antimicrobial resistance (AMR) of bacteria is increasing rapidly against all classes of antibiotics, with the increasing detection of carbapenem-resistant isolates. However, while growing prevalence has been reported around the world, data on the prevalence of carbapenem resistance in developing countries are fairly limited. In this study, we investigated and determined the resistance rate to carbapenems among multidrug-resistant Gram-negative bacteria (MDR-GNB) isolated in Djibouti and characterized their resistance mechanisms. Results: Of the 256 isolates, 235 (91.8%) were identified as Gram-negative bacteria (GNB). Of these GNBs, 225 (95.7%) isolates exhibited a multidrug resistance phenotype, and 20 (8.5%) isolates were resistant to carbapenems, including 13 Escherichia coli, 4 Acinetobacter baumannii, 2 Klebsiella pneumoniae and 1 Proteus mirabilis. The most predominant GNB in this hospital setting were E. coli and K. pneumoniae species. Carbapenemase genes such as blaOXA-48 and blaNDM-5 were identified, respectively, in six and four E. coli isolates, whereas the carbapenemase blaNDM-1 was identified in three E. coli, two K. pneumoniae, one P. mirabilis and one A. baumannii. Moreover, three A. baumannii isolates co-hosted blaOXA-23 and blaNDM-1. Materials and Methods: A total of 256 clinical strains collected between 2019 and 2020 were identified using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF). Antibiotic susceptibility testing was performed using disk diffusion and E-test methods. Real-time polymerase chain reaction (RT-PCR), standard PCR and sequencing were used to investigate genes encoding for extended-spectrum-β-lactamases, carbapenemases and colistin resistance genes. Conclusions: We report, for the first time, the presence of MDR-GNB clinical isolates and the emergence of carbapenem-resistant isolates in Djibouti. In addition to performing antimicrobial susceptibility testing, we recommend phenotypic and molecular screening to track the spread of carbapenemase genes among clinical GNB isolates.
Dissertations / Theses on the topic "Carbapenemase gram negative bacteria"
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Nascimento, Tatiane. "Ocorrência e diversidade de bactérias gram-negativas multirresistentes em ambientes aquáticos públicos no estado de São Paulo." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/42/42132/tde-26082015-175023/.
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Atividades antropogênicas relacionadas ao uso massivo de antibacterianos tem favorecido para que ambientes aquáticos sejam importantes locais para seleção e/ou disseminação de bactérias multirresistentes (MR). O objetivo do estudo foi monitorar a ocorrência de bactérias MRs em ambientes aquáticos públicos no estado de SP, caracterizando genótipos de resistência adquirida. Foram analisados 50 isolados de bactérias gram-negativas, recuperadas de amostras de água, sendo que 70% dos isolados apresentaram perfil de MR, identificando-se os genes blaCTX-M-2 (n= 5), blaCTX-M-9 (n= 1), blaCTX-M-15 (n= 2), blaKPC-2 (n= 3), qnrB (n= 1), oqxA (n= 3), oqxB (n= 3) e, aac(6)1b-cr (n= 7). Destaca-se a primeira detecção de A. calcoaceticus produtora de KPC-2. Ambientes aquáticos de acesso público podem ser importantes fontes para a disseminação e/ou transmissão de uma ampla variedade de espécies bacterianas MRs tanto para seres humanos como para ecossistemas associados, sendo que a presença de genótipos endêmicos sugere contaminação por esgoto doméstico e/ou hospitalar.<br>Anthropogenic activities related to the massive use of antibacterial has contributed to the selection and spread of multidrug-resistant (MDR) into the aquatic environment. This study aimed to monitor the occurrence of MDR bacteria in public aquatic environments, in the state of São Paulo, characterizing genotypes of acquired resistance. Of the 50 gram-negative isolates, recovered of water samples, 70% exhibited a MDR profile. Indeed, blaCTX-M-2 (n= 5), blaCTX-M-9 (n= 1), blaCTX-M-15 (n= 2)-, blaKPC-2 (n= 3)-, qnrB (n= 1)-, oqxA (n= 3)-, oqxB (n= 3)- and aac(6)-1b-cr (n = 7) genes were identified. Noteworthy is the first the detection of KPC-2-producing Acinetobacter calcoaceticus. Aquatic environments, with public access, may be important sources for the dissemination and/or transmission of a wide variety of MDR bacterial species to both humans and associated ecosystems. Moreover, the presence of endemic genotypes suggests contamination by domestic and/or hospital sewage.
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Muheim, Claudio. "Antibiotic uptake in Gram-negative bacteria." Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-148541.
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The increasing emergence and spread of antibiotic-resistant bacteria is a serious threat to public health. Of particular concern are Gram-negative bacteria such as Escherichia coli, Acinetobacter baumannii, Klebsiella pneumoniae or Pseudomonas aeruginosa. Some of these strains are resistant to a large number of antibiotics and thus our treatment options are rapidly declining. In addition to the increasing number of antibiotic-resistant bacteria, a major problem is that many of the antibiotics at our disposal are ineffective against Gram-negative bacteria. This is partly due to the properties of the outer membrane (OM) which prevents efficient uptake. The overarching goal of this thesis was to investigate how the OM of the Gram-negative bacterium E. coli could be weakened to improve the activity of antibiotics. In the first two papers of my thesis (paper I + II), I investigated the periplasmic chaperone network which consists of the two parallel pathways SurA and Skp/DegP. This network is essential for the integrity of the OM and strains lacking either SurA or Skp are defective in the assembly of the OM, which results in an increased sensitivity towards vancomycin and other antimicrobials. We identified a novel component of the periplasmic chaperone network, namely YfgM, and showed that it operates in the same network as Skp and SurA/DegP. In particular, we demonstrated that deletion of YfgM in strains with either a ΔsurA or Δskp background further compromised the integrity of the OM, as evidenced by an increased sensitivity towards vancomycin. In the remaining two papers of my thesis (paper III + IV), the goal was to characterize small molecules that permeabilize the OM and thus could be used to improve the activity of antibiotics. Towards this goal, we performed a high-throughput screen and identified an inhibitor of the periplasmic chaperone LolA, namely MAC-13243, and showed that it can be used to permeabilize the OM of E. coli (paper III). We further demonstrated that MAC-13243 can be used to potentiate the activity of antibiotics which are normally ineffective against E. coli. In the last paper of my thesis (paper IV), we undertook a more specific approach and wanted to identify an inhibitor against the glycosyltransferase WaaG. This enzyme is involved in the synthesis of LPS and genetic inactivation of WaaG results in a defect in the OM, which leads to an increased sensitivity to various antibiotics. In this paper, we identified a small molecular fragment (compound L1) and showed that it can be used to inhibit the activity of WaaG in vitro. To summarize, this thesis provides novel insights into how the OM of the Gram-negative bacterium E. coli can be weakened by using small molecules. We believe that the two identified small molecules represent important first steps towards the design of more potent inhibitors that could be used in clinics to enhance the activity of antibiotics.<br><p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p>
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Campbell, Joan Iyabo Amiemenoghena. "β-lactamase genes of gram-negative bacteria". Thesis, University of Edinburgh, 1986. http://hdl.handle.net/1842/15646.
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Two β-lactamase gene sequences encoded by <i>Ps. aeruginosa</i> RMS 149 plasmid and <i>Rps. capsulata</i> sp 108 were investigated. The genes were located using DNA recombinant techniques and their nucleic acid sequences were determined using the Sanger dideoxy-sequencing technique. The amino acid sequences were identified and compared with other characterised β-lactamases. They are both class A enzymes (Ambler classification). The pseudomonad plasmid encoded enzyme is expressed constitutively, but its gene sequence has an attenuator sequence - reminiscent of inducible bacterial synthetic operons. It also has three putative loop-forming sequences in the middle of the gene. RNA mapping studies indicate that the attenuator is read through from an upstream promoter. There is low level initiation from its own promoter and the transcripts sometimes terminate around the second internal stem-loop. The full message is also made. Thus, it is likely that the pseudomonad gene is normally highly regulated. Its constitutive expression may be as a result of some control mutation. The rhodopseudomonad enzyme is unlike other characterised Gram-negative class β-lactamases because it is inducible. Gene hybridization experiments suggest that it may be chromosomally encoded in strain sp 108 as well as in the Pen^S strain sp 109. β-lactamase active bands were also observed in Pen<SUP>S</SUP> <i>Rps. capsulata</i> St. Louis and <i>Rps. sphaeroides</i>. If this is the usual state of affairs in photosynthetic bacteria which are not normally subject to the selective pressures of the presence of β-lactam antibiotics by virtue of their aquatic habitat, the sp 108 strain may also be producing the enzyme in large quantities due to some control mutation. It is postulated then, that β-lactamase genes in Gram-negative bacteria may be of two kinds - one that is chromosomal and is highly regulated, and another which has lost the regulation and over-expresses the enzyme. The latter may be representative of the common plasmid-borne β-lactamase genes.
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Delvillani, F. "POST-TRANSCRIPTIONAL REGULATION IN GRAM NEGATIVE BACTERIA." Doctoral thesis, Università degli Studi di Milano, 2013. http://hdl.handle.net/2434/220058.
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Post-transcriptional regulation plays a pivotal role in gene expression control as it ensures a fast response to environmental changes. This is particularly important in unicellular organisms that are exposed to environmental changes. During my PhD, I studied different aspects of this type of regulation in two Gram-negative bacteria: Escherichia coli and the opportunistic pathogen Pseudomonas aeruginosa. In E. coli I investigated the role of the ribosomal protein S1 in the interplay between translation and mRNA decay. In particular we showed that S1 not associated to 30S can sequester and protect mRNA from RNase E, the main endonuclease in E. coli. Another aspect that I considered in my research has been regulation by RNA molecules in P. aeruginosa. In the last decade, it has become clear how RNA-based regulatory mechanisms are important in controlling bacterial gene expression. However, little is known about it in this relevant human pathogen. By RNA deep sequencing we identified more than 150 novel candidate sRNAs in the P. aeruginosa strains PAO1 and PA14, which differ in virulence degree. We confirmed by Northern blotting the expression of 52 new sRNAs, substantially increasing the number of known sRNAs expressed by this bacterium. In this context we developed a genetic screen for the identification of genes post-transcriptionally regulated by RNA determinants and applied this system to the search of RNA thermometers (RNATs), i.e. mRNA determinants that couple translation with temperature changes. We identified four putative RNATs and validated two of them in E. coli. Interestingly, the two are located upstream of genes previously implicated in P. aeruginosa pathogenesis, namely dsbA and ptxS. ptxS RNAT was validated also in P. aeruginosa and represents the first RNAT ever described in this bacterium.
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Fusté, i. Domínguez Ester. "Epigenetics of Antimicrobial Resistance in Gram-Negative Bacteria." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/97096.
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Resistance to antimicrobials is a well-known phenomenon leading to difficulties in the treatment of infectious diseases. The genetic determinants of such resistance are in general well understood: plasmids, transposons, insertion sequences and integrons are the most frequently related genetic elements.
The word epigenetics refers to changes in the phenotype or in the gene expression caused by mechanisms other than underlying DNA sequence. In some cases these changes can remain for generations.
Serratia marcescens is an enterobacterium characterized by its natural (intrinsic) resistance to most antibiotics. It is also a relevant opportunistic pathogen which has been involved in several pathologies such as urinary tract infections, prostheses infections, cellulitis, bacteremia and others.
P. aeruginosa is a Gram-negative bacterium considered one of the major nosocomial pathogens worldwide. It causes several infections such as wound and burn infections as well as respiratory tract infections mostly affecting cystic fibrosis patients.
An increasing prevalence of infections caused by multidrug-resistant (MDR) isolates has been reported in many countries and is actually a cause of concern. Both, P. aeruginosa and S. marcescens are relevant nosocomial pathogens.
Some of the classic antimicrobials used to treat these pathogens are out-of-date and several of the new drugs available have already become targets for bacterial mechanism of resistance.
Environmental conditions exert high pressure not only in the selection of genes encoding resistance to antibiotics or integron fixation in bacterial genomes or plasmids and other mobile elements transmission, but also in the expression of these potentialities that leads to resistance. Thus the role of epigenetics remains to be investigated. In addition it is well known that bacteria causing infections are naturally forming part of biofilms instead the planktonic way of life normally assumed to be in laboratory conditions.
The aim of this thesis was the study of unconventional mechanisms of antimicrobial resistance contributing to MDR phenotypes in both S.marcescens and P. aeruginosa. Also the exploration of changes in antimicrobial susceptibilities of Serratia marcescens in the last 50 years by comparing isolates collected between 1945 and 1950, and current isolates.
¬The main conclusions obtained from this study are:
1. The resistome of Serratia marcescens did not change significantly during the antibiotic era.
2. Antibiotic withdrawing tends to restore original susceptible phenotypes, irrespective to the molecular mechanism involved in resistance.
3. None of Serratia strains studied presented integrons, any extended spectrum ß-lactamases.
4. Phenotypically determination of susceptibilities of old strains inactive during the last 60 years have confirmed results obtained by metagenomics i.e. the genes of resistance already existed before antibiotics discovery and use.
5. Multiresistant Pseudomonas aeruginosa harbored class 1 integrons containing a cassette encoding aminoglycoside adenylyltransferase (aadB).
6. Multiresistant Pseudomonas aeruginosa overexpressed MexAB-OprM and MexXY efflux machinery.
7. CCCP use should be avoided in experiments performed with P. aeruginosa and probably in other aerobic bacteria.
8. Meropenem induces the formation of aberrant long rods which can survive, accumulate less antibiotic than normal bacteria, and can revert to normal forma when antibiotic pressure disappears.
9. Colistin, the last therapeutic option to fight against Pseudomonas infections in cystic fibrosis patients, is normally active although cases of resistance have arisen recently.
10. Resistance to colistin seems to be mediated by lipopolysaccharide singular properties.
11. Colistin induces injuries in lipid bilayers, which can be studied by means of planar black lipid bilayer techniques. Preliminary results showed the ability of colistin to induce transient channels in the bilayers, with some dependence to voltage.
12. Recovery of susceptibility to imipenem is slower than acquision of resistance, since the selective advantage conferred by imipenem resistance in the presence of the antimicrobial is strong whereas OprD expression is likely evolutionarily advantageous only under certain and unknown environmental conditions.<br>Es van explorar els mecanismes no convencionals de resistència als agents antimicrobians que contribueixen a l’aparició de fenotips multiresistents en els bacteris Gram-negatius Serratia marcescens i Pseudomonas aeruginosa.
Es van examinar també els canvis en la susceptibilitat als agents antimicrobians en S. marcescens durant els darrers 50 anys, comparant soques aïllades entre els anys 1945-1950 y soques actuals.
¬Les principals conclusions obtingudes d’aquest estudi són les següents:
1. El resistoma de Serratia marcescens no ha canviat significativament des de l’era pre-antibiòtica fins l’actualitat.
2. La retirada dels antibiòtics tendeix a recuperar els fenotips de susceptibilitat originals, independentment del mecanisme molecular implicat en la resistència.
3. Cap de las soques de Serratia estudiades va presentar integrons ni tampoc ß-lactamases d’espectre estès.
4. La determinació fenotípica de les susceptibilitats de las soques “antigues” de Serratia inactives durant 60 anys ha confirmat els resultats obtinguts mitjançant metagenòmica, és a dir, els gens de resistència als antibiòtics ja existien amb anterioritat al descobriment i ús dels antibiòtics.
5. En les soques clíniques de P. aeruginosa multiresistents es va detectar un integró de classe 1 que contenia el cassette gènic aadB, que codifica l’enzim aminoglicòsid 2’-O- adeniltransferasa, que confereix resistència a gentamicina, tobramicina i kanamicina.
6. Les soques multiresistents de P. aeruginosa van sobreexpressar els sistemes de reflux MexAB-OprM i MexXY-OprM.
7. L’ús de l’inhibidor de bombes de reflux CCCP s’hauria d’evitar als experiments realitzats amb P. aeruginosa i probablement amb altres bacteris de metabolisme aeròbic.
8. El meropenem indueix la formació de llargs bacils aberrants capaços de sobreviure en presència de l’antibiòtic. Aquests bacils acumulen menys antibiòtic que els bacteris normals, i poden revertir a la forma normal quan s’elimina la pressió selectiva.
9. La colistina, la última alternativa terapèutica per lluitar contra P. aeruginosa en pacients amb fibrosis quística, és normalment efectiva, encara que recentment han sorgit casos de resistència a aquest agent antimicrobià.
10. La resistència a colistina sembla estar causada per propietats singulars del lipopolisacàrid.
11. La colistina produeix danys en les membranes lipídiques que poden ser estudiats mitjançant tècniques de Black lipid bilayer. Estudis preliminars van mostrar la capacitat de la colistina para induir canals transitoris en les bicapes lipídiques, amb certa dependència de voltatge.
12. La recuperació de la susceptibilitat a l’imipenem en P. aeruginosa és més lenta que l’adquisició de resistència, donat que l’avantatge selectiva conferida per la resistència a l’imipenem en presència de l’agent antimicrobià és forta, mentre que l’expressió d’ OprD és probablement avantatjosa solament sota certes i desconegudes condicions ambientals.<br>Se exploraron los mecanismos no convencionales de resistencia a agentes antimicrobianos que contribuyen a la aparición de fenotipos multiresistentes en las bacterias Gram-negativas Serratia marcescens y Pseudomonas aeruginosa. Se examinaron también los cambios en la susceptibilidad a los agentes antimicrobianos en S. marcescens en los últimos 50 años, comparando cepas aisladas entre los años 1945-1950 y cepas actuales.
¬Las principales conclusiones obtenidas de este estudio son las siguientes:
1. El resistoma de Serratia marcescens no ha cambiado significativamente desde la era pre-antibiótica hasta la actualidad.
2. La retirada de los antibióticos tiende a recuperar los fenotipos de susceptibilidad originales, independientemente del mecanismo molecular implicado en la resistencia.
3. Ninguna de las cepas de Serratia estudiadas presentó integrones ni tampoco ß-lactamasas de espectro extendido.
4. La determinación fenotípica de las susceptibilidades de las cepas “antiguas” de Serratia inactivas durante 60 años ha confirmado los resultados obtenidos mediante metagenómica, es decir, los genes de resistencia a los antibióticos ya existían con anterioridad al descubrimiento y uso de los antibióticos.
5. En las cepas clínicas de P. aeruginosa multiresistentes se detectó un integrón de clase 1 que contenía el cassette génico aadB, que codifica la enzima aminoglicósido 2’-O- adeniltransferasa, que confiere resistencia a gentamicina, tobramicina y kanamicina.
6. Las cepas multiresistentes de P. aeruginosa sobreexpresaron los sistemas de reflujo MexAB-OprM y MexXY-OprM.
7. El uso del inhibidor de bombas de reflujo CCCP se debería evitar en los experimentos realizados con P. aeruginosa y probablemente con otras bacterias de metabolismo aeróbico.
8. El meropenem induce la formación de largos bacilos aberrantes capaces de sobrevivir en presencia del antibiótico. Estos bacilos acumulan menos antibiótico que las bacterias normales, y pueden revertir a la forma normal cuando se elimina la presión selectiva.
9. La colistina, la última alternativa terapéutica para luchar contra P. aeruginosa en pacientes con fibrosis quística, es normalmente efectiva, aunque recientemente han surgido casos de resistencia a este agente antimicrobiano.
10. La resistencia a colistina parece estar mediada por propiedades singulares del lipopolisacárido.
11. La colistina produce daños en las membranas lipídicas que pueden ser estudiados mediante técnicas de Black lipid bilayer. Estudios preliminares mostraron la capacidad de la colistina para inducir canales transitorios en las bicapas lipídicas, con cierta dependencia de voltaje.
12. La recuperación de la susceptibilidad al imipenem en P. aeruginosa es más lenta que la adquisición de resistencia, dado que la ventaja selectiva conferida por la resistencia al imipenem en presencia del agente antimicrobiano es fuerte, mientras que la expresión de OprD es probablemente ventajosa sólo bajo ciertas y desconocidas condiciones ambientales.
6
Chan, Anson Chi-Kit. "Iron transport in two pathogenic Gram-negative bacteria." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/32406.
Full textAbstract:
Campylobacter jejuni and Escherichia coli strain F11 are two Gram-negative pathogens with a versatile armament of iron uptake systems to cope with the fluctuating host nutrient environment. Our current understanding of Gram-negative iron uptake systems focuses heavily on a prototypical scheme involving a TonB-dependent outer membrane receptor and an ABC transporter, with little knowledge on systems that do not fall neatly into this paradigm. The primary focus of this thesis is the characterization of three such atypical iron uptake proteins from C. jejuni (ChaN and P19) and pathogenic E. coli (FetP).
C. jejuni ChaN is a 30 kDa, iron-regulated lipoprotein hypothesized to be involved in iron uptake. The crystal structure of ChaN reveals that it can bind two cofacial heme groups in a pocket formed by a ChaN dimer. Each heme iron is coordinated by a single tyrosine from one monomer and the propionate groups are hydrogen bonded by a histidine and a lysine from the other monomer. Analytical ultracentrifugation studies demonstrate heme-dependent dimerization in solution. Cell fractionation of C. jejuni shows that ChaN is localized to the outer membrane. Based on these findings, the predicted in vivo role of ChaN in iron uptake is discussed.
C. jejuni cFtr1-P19 and E. coli FetMP are homologous iron-regulated systems also proposed to be iron transporters. Through growth studies in both organisms, we show that P19 and FetMP are required for optimal growth under iron-limited conditions. Furthermore, metal binding analysis demonstrates that recombinant P19 and FetP bind both copper and iron. Dimerization of P19 is shown to be metal dependent in vitro and is detected in vivo by cross-linking. Through x-ray crystallography, we have determined the structures of P19 and FetP with various metals bound, thus revealing the locations of the highly conserved copper and iron binding sites. Additionally, the crystal structure of FetP reveals two copper positions in each binding site that is likely functionally important. Through mutagenesis, residues contributing to the alternative copper positions were identified. Together, these studies provide insight into the mechanism of iron transport by the two systems and allow for the development of functional models.
7
Wallace, Jeremy Iain. "Hyperinducible β-lactamase expression in gram-negative bacteria." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295568.
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8
Ismael, Mariam Mohamed. "Bioremediation of hexavalent chromium using gram-negative bacteria." Thesis, Sheffield Hallam University, 2014. http://shura.shu.ac.uk/19859/.
Full textAbstract:
Hexavalent chromium (Cr (VI)), the most toxic form of chromium, is widely used in industrial processes. As a result substantial amounts of Cr (VI) contaminated wastes are produced. The use of microbial cells as bioremediation of heavy metals is a potential alternative to conventional chemical methods. In this work, laboratory- scale experiments were performed to investigate Cr (VI) removal using five environmental Gram-negative bacterial strains, three of which were nosocomial strains. The potential of live and autoclaved bacterial strains was investigated to mitigate Cr (VI) from its initial concentration of 2.54 mg/1. The autoclaved bacteria were used to determine whether Cr (VI) removal was dependent upon metabolism of the cells or a simple chemical reaction. The results showed notable reduction in Cr (VI) concentration (up to 87% and 23% using live and autoclaved bacteria, respectively). Proteus mirabilis and Methylococcus capsulatus (Bath) bacterial strains were selected for further detailed analyses to investigate the enzyme system that is responsible for Cr (VI) reduction. To locate the cell compartment in which Cr (VI) removal took place in P. mirabilis, a standard bacterial cell fractionation method was used. The highest Cr (VI) removal activity resided in the cytoplasm, and there was also some activity in the cell membrane. No chromium VI removal was observed in the cell wall fraction. The removal by M. capsulatus of Cr (VI) in high copper sulfate media was more rapid than in low copper sulfate media. Phenylacetylene, an inhibitor of soluble methane monooxygenase, completely inhibited Cr (VI) removal. The results reveals that pMMO, sMMO or other enzymes that induced by copper were involved in reducing or otherwise removing Cr (VI). The di-heme cytochrome c peroxidase is also a possible candidate enzyme of reducing chromium (VI), since it is known to be present in the periplasm and to play a role in reducing peroxides generated by oxidative metabolism. Inductively coupled plasma mass spectrometry coupled with ion chromatography, for the determination of chromium species in P. mirabilis and M. capsulatus, showed that Cr (VI) was reduced and detoxified to less toxic and less soluble Cr (III). Furthermore, prominent changes in the polysaccharide, fatty acids, phosphate and proteins wereobserved in FTIR spectra of P. mirabilis and M. capsulatus (Bath) with potassium dichromate. These changes were consistent with the adsorption of chromium. BLAST searches using known chromate (VI) reducing enzymes from other bacteria showed a presence of four significant potential chromate reductase genes in the genome sequence of P. mirabilis. During the growth of M. capsulatus (Bath), it was noticed that a contaminant bacterium appeared in some cell cultures. The contaminant bacterium was identified as Bacillus licheniformis (100%) using PCR and 16S rRNA sequencing. The mixed culture that contains M. capsulatus (Bath) plus Bacillus licheniformis was also tested for Cr (VI) mitigation. The results of this work are a step forward in understanding the potential of environmental microorganisms for remediation of hexavalent chromium contamination. The future work may reveal more about the mechanism of Cr (VI) removal by the bacteria studied here as well as how they can be exploited for practical bioremediation.
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BERTINI, ALESSIA. "Plasmid-mediated antimicrobial resistance in Gram-negative bacteria." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/641.
Full textAbstract:
L’epidemiologia dei plasmidi di resistenza è il principale mezzo per descrivere la diffusione
delle resistenze agli antimicrobici. L’identificazione di plasmidi correlati associati a specifici geni di
resistenza può aiutare a tracciare la disseminazione di plasmidi epidemici, aprendo nuovi scenari
epidemiologici sui meccanismi di diffusione delle resistenze agli antimicrobici. Questo aspetto è
particolarmente evidente quando si considerano plasmidi che sono associati alla diffusione delle
Beta Lattamasi a Spettro Esteso (ESBL) come gli enzimi CTX-M, SHV, TEM.
Lo scopo di questa tesi è stato quello di caratterizzare plasmidi che conferiscono resistenza
a farmaci rilevanti per la terapia umana in differenti collezioni di Enterobacteriaceae di origine
umana e animale. Verranno discussi diversi esempi di plasmidi epidemici quali: i plasmidi
IncHI2 che trasportano i geni blaCTX-M-9 o blaCTX-M-2 provenienti da isolati di origine
umana e animale di Escherichia coli e Salmonella dalla Spagna, Belgio e Inghilterra; i plasmidi
IncI1 caratterizzati da specifici fattori di virulenza, che trasportano i geni blaTEM-52 e
blaCTX-M-1 derivanti da isolati di Salmonella e E. coli di origine umana e animale; i plasmidi
IncN che trasportano i geni codificanti la metallo-β-lattamasi VIM-1 da isolati umani di
Klebsiella pneumoniae and E. coli dalla Grecia; plasmidi IncA/C2 associati a specifici geni di
resistenza come blaCMY-2, blaCMY-4, blaVIM-4 e blaVEB-1 provenienti da diverse
Enterobacteriaceae isolate in differenti parti del mondo, ed infine, i plasmidi associati all’enzima
SHV-12 isolati in diverse Enterobacteriaceae di origine umana e animale.
L’analisi mediante comparazione della struttura plasmidica ha permesso di rilevare la diffusione
di plasmidi emergenti e consente di tracciare i percorsi evolutivi e di diffusione attraverso l’acquisizione
di una vastità di elementi genetici mobili associati ai geni di resistenza.<br>The epidemiology of resistance plasmids is a major issue for the description of antimicrobial resistance
diffusion. The identification of related plasmids associated to specific resistance genes may
help to follow the spread of epidemic plasmids, opening new epidemiological scenarios on the
mechanism of diffusion of antimicrobial resistance. This aspect is particularly interesting when
applied to collections of plasmids that are playing a major role in the diffusions of Extended
Spectrum Beta Lactamases (ESBLs) such as CTX-M, SHV, TEM.
The aim of this thesis is the molecular characterization of plasmids conferring drug resistances
in different collections of Enterobacteriaceae of human and animal origin. Several example
of epidemic plasmids will be discussed: the IncHI2 plasmids carrying blaCTX-M-9 or blaCTX-M-2
genes identified from human and animal isolates of Escherichia coli and Salmonella from Spain,
Belgium and UK; the IncI1 family of plasmids characterized by specific virulence factors, carrying
the blaCMY-2, blaTEM-52 and blaCTX-M-1 genes from Salmonella and E. coli of human and animal
origin; the IncN plasmids carrying the gene codifying the metallo-β-lacatamase VIM-1 from
human isolates of Klebsiella pneumoniae and E. coli in Greece; the IncA/C2 plasmids carrying
specific resistance genes such as blaCMY-2, blaCMY-4, blaVIM-4 and blaVEB-1 from different
Enterobacteriaceae isolated worldwide; different plasmid replicons (IncFII, IncA/C1, IncI1) carrying
the ESBL SHV-12 from human and animal origin.
The comparative analysis of plasmid backbones allowed to ascertain the diffusion of common,
emerging plasmids and helped to determine the evolution of these plasmids by acquisition
of relevant resistance genes by a panoply of mobile genetic elements and illegitimate recombination
events.
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ACOSTA, GUTIERREZ SILVIA. "Permeability in Gram-negative bacteria: A microscopic journey." Doctoral thesis, Università degli Studi di Cagliari, 2017. http://hdl.handle.net/11584/248736.
Full textAbstract:
Bacteria multi-drug resistance is a challenging problem of contemporary medicine and a new molecular framework for antibiotics is needed. General bacterial porins are recognized as the main pathway for polar antibiotics, but the permeability rules are still under debate. Recent works in literature pointed the electrostatics of the channel to be responsible for its filtering mechanism, and some theoretical investigations are already reported in the literature aimed at characterizing the electrostatics inside water-filled channels.
Using Molecular dynamics simulations we revealed the electrostatic filtering mechanism for porins, using water as sensing tool. We further quantify from water polarization density inside the channel the macroscopic internal electric field inside porins. This method allowed us to put forward an ultra-coarse-grained model in which the channel is described by its cross-section area, internal electric field and electrostatic potential along the axis of diffusion. Once these three descriptors are defined, it is possible to estimate the whole free energy along the channel axis of diffusion for a molecule represented by its size, charge and electric dipole moment in a few seconds.
This model would allow to virtually screening libraries of molecules searching for hits with enhanced permeability. These results may have important implications for the formulation of a general model for antibiotics translocation, and can be taken into account for rational drug design.<br>Bacteria multi-drug resistance is a challenging problem of contempo-
rary medicine and a new molecular framework for antibiotics is needed.
General bacterial porins are recognized as the main pathway for po-
lar antibiotics, but the permeability rules are still under debate. Recent
works in literature pointed the electrostatics of the channel to be respon-
sible for its filtering mechanism, and some theoretical investigations are
already reported in the literature aimed at characterizing the electrostat-
ics inside water-filled channels.
Using Molecular dynamics simulations we revealed the electrostatic
filtering mechanism for porins, using water as sensing tool. We further
quantify from water polarization density inside the channel the macro-
scopic internal electric field inside porins. This method allowed us to
put forward an ultra-coarse-grained model in which the channel is de-
scribed by its cross-section area, internal electric field and electrostatic
potential along the axis of diffusion. Once these three descriptors are
defined, it is possible to estimate the whole free energy along the chan-
nel axis of diffusion for a molecule represented by its size, charge and
electric dipole moment in a few seconds.
This model would allow to virtually screen libraries of molecules
searching for hits with enhanced permeability. These results may have
important implications for the formulation of a general model for antibiotics translocation, and can be taken into account for rational drug
design.
Books on the topic "Carbapenemase gram negative bacteria"
1
American Society for Microbiology. Committee on Continuing Education. and American Society for Microbiology. Meeting, eds. Rare gram-negative rods. American Society for Microbiology, 1986.
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2
M, Thomas Christopher, ed. Promiscuous plasmids of gram-negative bacteria. Academic Press, 1989.
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3
Shahid, Mohammad, Anuradha Singh, and Hiba Sami, eds. Beta-Lactam Resistance in Gram-Negative Bacteria. Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-9097-6.
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4
Backert, Steffen, and Elisabeth Grohmann, eds. Type IV Secretion in Gram-Negative and Gram-Positive Bacteria. Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-75241-9.
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5
A, Clark William, and Centers for Disease Control (U.S.), eds. Identification of unusual pathogenic gram-negative aerobic and facultatively anaerobic bacteria. U.S. DHHS, PHS, Centers for Disease Control ; Washington, D.C. : For sale by the Supt. of Docs., U.S. G.P.O., 1985.
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6
1932-, Gilardi Gerald L., ed. Nonfermentative gram-negative rods: Laboratory identification and clinical aspects. M. Dekker, 1985.
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7
Weaver, Robert E. Gram-negative organisms: An approach to identification (guide to presumptive identification). U.S. Dept. of Health and Human Services, Public Health Service, Centers for Disease Control, 1985.
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8
Weaver, Robert E. Gram-negative organisms: An approach to identification (guide to presumptive identification). U.S. Dept. of Health and Human Services, Public Health Service, Centers for Disease Control, 1985.
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9
S, Weyant Robin, ed. Identification of unusual pathogenic gram-negative aerobic and facultatively anaerobic bacteria. 2nd ed. Williams & Wilkins, 1996.
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10
Dixit, Sameer M., and Kasipathy Kailasapathy. Antagonistic activity and interaction of probiotic bacteria with intestinal microbiota. Nova Science Publishers, 2012.
Find full textBook chapters on the topic "Carbapenemase gram negative bacteria"
1
Tuwairqi, Khaled. "Gram-Negative Bacteria." In Encyclopedia of Ophthalmology. Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-35951-4_796-1.
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2
Martin, Craig A. "Gram-Negative Bacteria." In Management of Antimicrobials in Infectious Diseases. Humana Press, 2009. http://dx.doi.org/10.1007/978-1-60327-239-1_3.
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Grossman, Marc E., Lindy P. Fox, Carrie Kovarik, and Misha Rosenbach. "Gram-Negative Bacteria." In Cutaneous Manifestations of Infection in the Immunocompromised Host. Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-1578-8_13.
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4
Amils, Ricardo. "Gram-Negative Bacteria." In Encyclopedia of Astrobiology. Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-27833-4_663-3.
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5
Amils, Ricardo. "Gram-Negative Bacteria." In Encyclopedia of Astrobiology. Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_663.
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6
Tuwairqi, Khaled. "Gram-Negative Bacteria." In Encyclopedia of Ophthalmology. Springer Berlin Heidelberg, 2018. http://dx.doi.org/10.1007/978-3-540-69000-9_796.
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7
Amils, Ricardo. "Gram Negative Bacteria." In Encyclopedia of Astrobiology. Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_663.
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8
Rapp, Robert P., and Kenneth E. Record. "Gram-Negative Bacteria." In Management of Antimicrobials in Infectious Diseases. Humana Press, 2001. http://dx.doi.org/10.1007/978-1-59259-036-0_3.
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Amils, Ricardo. "Gram-Negative Bacteria." In Encyclopedia of Astrobiology. Springer Berlin Heidelberg, 2023. http://dx.doi.org/10.1007/978-3-662-65093-6_663.
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Van Vuuren, H. J. J. "Gram-negative spoilage bacteria." In Brewing Microbiology. Springer US, 1996. http://dx.doi.org/10.1007/978-1-4757-4679-2_6.
Full textConference papers on the topic "Carbapenemase gram negative bacteria"
1
Barrera-Patiño, Claudia P., Jennifer M. Soares, Kate C. Blanco, Natalia M. Inada, and Vanderlei Salvador Bagnato. "Identification of antibiotic resistance susceptibility in different species of microorganisms implementing machine learning." In Latin America Optics and Photonics Conference. Optica Publishing Group, 2024. https://doi.org/10.1364/laop.2024.tu4a.20.
Full textAbstract:
Based in previous publish work [1], in this study, we highlight the importance of building robust machine learning foundations to differentiate antimicrobial resistance involving between gram-negative and gram-positive bacteria. This advance is crucial to be applied to clinical needs.
2
Kramer, J. F. "Peracetic Acid: A New Biocide for Industrial Water Applications." In CORROSION 1997. NACE International, 1997. https://doi.org/10.5006/c1997-97404.
Full textAbstract:
Abstract Peracetic acid is rapidly cidal at low concentrations against a broad spectrum of microorganisms, including gram-positive and gram-negative bacteria, yeasts, molds, and algae under a wide variety of conditions. It is also effective against anaerobic and spore forming bacteria. Peracetic acid is effective at killing biofilm microorganisms at low concentrations and short contact times. Unlike a number of other biocides, the biocidal activity of peracetic acid is not affected by pH or water hardness and biocidal activity is retained even in the presence of organic matter. For these reasons, peracetic acid is well suited as a biocide in industrial cooling water and papermaking systems. Peracetic acid is compatible with additives commonly used in these systems. Although peracetic acid is a potent biocide, it is unique in that it does not produce toxic byproducts and its decomposition products, acetic acid, water and oxygen, are innocuous and environmentally acceptable.
3
Caraba, Marioara Nicoleta, Valeriu Caraba, Gabi Dumitrescu, Elena Pet, and Roxana Popescu. "ANTIMICROBIAL POTENTIAL OF METHANOLIC AND N-HEXANE EXTRACTS OF VISCUM ALBUM." In SGEM International Multidisciplinary Scientific GeoConference 24. STEF92 Technology, 2024. https://doi.org/10.5593/sgem2024/6.1/s25.19.
Full textAbstract:
Plants are sources of compounds with medicinal potential, an impressive number of medicines have in their composition compounds isolated from natural sources, many of them being used since ancient times, in traditional medicine. Aromatic and medicinal plants are sources of various nutrients and non-nutritive molecules, many of which exhibit antimicrobial and antioxidant properties. V. album extracts have a complex chemical composition, some of the identified compounds being responsable for their antibacterial and antifungal potential. The chemical composition of V. album extracts differs depending on the provenance and especially with respect to the host plant. The antimicrobial effect of extracts in methanol and n-hexane from leaves and young branches of V. album was tested by the diffusimetric method on agar. In the study, five concentrations were tested for each extract, on four Gram positive bacterial strains: Streptoccoccus pyogenes, Enterococcus faecalis, Clostridium perfringens, Staphylococcos aureus and three Gram negative: Escherichia coli, Pseudomonas aeruginosa, Legionella pneumophila, respectively two antibiotics: ampicillin and chloramphenicol were used as a reference control. Gram+ and Gram- bacterial strains showed an intermediate sensitivity at the first two concentrations tested for both extracts (methanolic and n-hexane), after which the antibacterial potential decreases with the decrease in concentration until it disappears completely. The effects of the methanolic extract of V. album is more obvious in Gram+ bacteria compared to Gram-. The n-hexane extract of V. album determines an antimicrobial effect only at the first concentrations tested, there are variations depending on the bacterial strain.
4
Okeniyi, Joshua Olusegun, Taiwo Felicia Owoeye, Abimbola Patricia Idowu Popoola, et al. "Performance of Hura Crepitans Mediated Ag-Nanoparticle Material on the Inhibition of Microbes Inducing Microbiologically-Influenced-Corrosion." In CORROSION 2018. NACE International, 2018. https://doi.org/10.5006/c2018-10916.
Full textAbstract:
Abstract The performance of Hura crepitans mediated Ag (silver) nanoparticle material on the inhibition of microbes (including six bacteria and a fungus strain) inducing microbiologically-influenced-corrosion (MIC) of metals was investigated in this paper. Leaf-extract was obtained from the Hura crepitans for use as a precursor for the Ag-nanoparticle synthesis, which was then characterised by the instrumentation of scanning electron microscopy and energy dispersive spectroscopy (SEM+EDS). The natural plant-mediated Ag-nanoparticle material was then utilised for sensitivity and/or resistance experimental investigations against three Gram-positive and three Gram-negative bacteria and a fungus strains of microbes that are known to induce microbiologically-influenced-corrosion in metallic materials. From this, the inhibition of microbial growth by the plant-extract mediated Ag-nanoparticle was compared with that from a commercial antibiotic that was used as the control. From the results, it was established that all the microbial strains studied were sensitive to the Hura crepitans mediated Ag-nanoparticle material while three out of the seven microbial strains for the study were resistant to the control antibiotic chemical. The implications and recommendations, ensuing from these results, on the use of the bio-mediated Ag-nanoparticle in MIC mitigation/control applications are detailed in the study.
5
Paula, BG, YP Donetti, TD Dino, and S. Vieira. "KLEBSIELLA PNEUMONIAE KPC HOSPITALAR NO HOSPITAL JAPONÊS SANTA CRUZ EM 2022." In Resumos do 54º Congresso Brasileiro de Patologia Clínica/Medicina Laboratorial. Zeppelini Editorial e Comunicação, 2022. http://dx.doi.org/10.5327/1516-3180.140s1.6189.
Full textAbstract:
Objetivo: No Brasil, desde o relato do primeiro caso em 2006, o número de infecções por K. pneumoniae produtoras de KPC elevou-se consideravelmente, com disseminação dessas cepas entre as UTIs dos hospitais, agravando o quadro clínico dos pacientes admitidos e aumentando a permanência da internação. Método: A coinfecção pela Covid é facilitada pelo comprometimento do sistema imune do paciente, que pode já ser deficiente – em razão da idade avançada e da presença de doenças crônicas, tais como hipertensão, diabetes e obesidade – ou pela sua atuação na infecção pelo novo coronavírus. O enfraquecimento da imunidade biológica é o responsável por tornar o organismo humano mais suscetível à infecção por bactérias que estavam apenas colonizando o corpo. São componentes importantes do nosso sistema imune, ajudando a proteger nossas mucosas, incluindo a respiratória. Há três mecanismos que contribuem com isso, são eles: competição da bactéria ruim pela adesão às células da superfície da mucosa, competição pelos nutrientes (derivados dos alimentos) disponíveis e produção de substâncias antibacterianas que matam outras bactérias. Conclusão: Apesar de baixas infecções por KPC no Hospital Japonês Santa Cruz, tivemos aumento significativo em materiais de culturas em geral, mantendo o índice negativo de hemocultura e apenas um caso em urocultura desde janeiro. Referências: 1. Koneman EW et al. Diagnóstico microbiológico. 5 ed. Rio de Janeiro: Editora Médica e Científica; 2001. 2. Bush K. New beta-lactamases in Gram-negative bacteria: diversity and impact on the election of antimicrobial therapy. Clin Infect Dis, 2001. 3. Klebsiella pneumoniae produtora de carbapenemase do tipo KPC: disseminação mundial e situação atual no Brasil, 2019. Faculdade Única-MG. 4. Índice epidemiológico do estado de São Paulo, 2022. Disponível em: https://www.saopaulo.sp.gov.br/noticias-coronavirus.
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Seija, V., V. Rocha, C. Tabarez, et al. "DETECCIÓN RÁPIDA DE ENTEROBACTERALES PRODUCTORES DE CARBAPENEMASAS Y ß-LACTAMASAS DE ESPECTRO EXTENDIDO DIRECTAMENTE A PARTIR DE HEMOCULTIVOS POSITIVOS." In Resumos do 55º Congresso Brasileiro de Patologia Clínica/Medicina Laboratorial. Zeppelini Editorial e Comunicação, 2023. http://dx.doi.org/10.5327/1516-3180.141s2.9609.
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Meta: Evaluar la capacidad de las pruebas HB&L-ESBL/AmpC® and HB&L-Carbapenemase® kits (ALIFAX) para detectar Enterobacterales productores de carbapenemasas y beta lactamasas de espectro extendido (BLEE) y/o AmpC desreprimida en caldo de hemocultivos positivos. Método: Se incluyeron 111 cepas conocidas de Enterobacterales, 41 productoras de BLEE y/o AmpC, 33 de carbapenemasas (EPC) y resto sin estos mecanismos de resistencia. Se inoculó 10 ul de una suspensión 0,5 Mc Farland de la cepas conocidas en frascos de hemocultivos descargados anteriormente como negativos. Cuando el hemocultivo dio aviso positivo se siguieron las recomendaciones del fabricante para el procesamiento con ambas pruebas: HB&L-ESBL/AmpC® y HB&L-Carbapenemase® kits. HB&L Carbapenemase kit fue capaz de detectar los 33 hemocultivos inoculados con aislamientos de EPC mostrando curvas de crecimiento bacteriano ascendente. De las cepas negativas para EPC (n = 78) detectó una como positiva. Por tanto, mostró una sensibilidad de 100% (IC 95% 89,6-100) y una especificidad de 98,7% (IC95% 93,1-99,8). ESBL/AmpC kit detectó como positivos los 33 hemocultivos inoculados con EPC y 39/41 de los inoculados con BLEE y/o AmpC desrreprimida y uma cepa sin mecanismos de resistencia. Por tanto, mostró una sensibilidad de 97,3% (IC 95% 90,7-99,3) y una especificidad de 97,3% (IC95% 86,2-99,5). Conclusión: Ambas pruebas mostraron una performance excelente en relación a la sensibilidad y especificidad permitiendo la detección precoz de bacteriemias causadas por BLEE y carbapenemasas en comparación con los métodos convencionales. Estas pruebas tienen un costo menor que las pruebas moleculares y las inmunocromatográficas con un gran potencial para ser utilizadas en instituciones sanitarias de baja y mediana complejidad, donde estos mecanismos de resistencia sean frecuentes y en las cuales actualmente sólo se utilicen métodos tradicionales.
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HAN, DONGDONG, CAIYUAN YU, and YUJUN ZHOU. "MICROENCAPSULATION OF GRAM-NEGATIVE BACTERIA BY SPRAY DRYING." In The Proceedings of the 5th Asia-Pacific Drying Conference. World Scientific Publishing Company, 2007. http://dx.doi.org/10.1142/9789812771957_0013.
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Xiao, Zhiwen. "Antimicrobial resistance mechanisms: using examples from gram-positive and gram-negative bacteria." In International Conference on Biological Engineering and Medical Science (ICBIOMed2022), edited by Gary Royle and Steven M. Lipkin. SPIE, 2023. http://dx.doi.org/10.1117/12.2669646.
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Sysolyatina, E. V., M. A. Yurova, A. Y. Mukhachev, et al. "The bactericidal effect of a positive and negative corona on Gram-positive and Gram-negative bacteria." In 2012 IEEE 39th International Conference on Plasma Sciences (ICOPS). IEEE, 2012. http://dx.doi.org/10.1109/plasma.2012.6383778.
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Rizqi, Hamdan Dwi, Nurmala Maulidina Helayanti, and Adi Setyo Purnomo. "Potential of Adenium obesum flowers extracts as an antibacterial against gram-negative bacteria and gram-positive bacteria." In THE FOURTH AL-NOOR INTERNATIONAL CONFERENCE FOR SCIENCE AND TECHNOLOGY (4NICST2022). AIP Publishing, 2024. http://dx.doi.org/10.1063/5.0206444.
Full textReports on the topic "Carbapenemase gram negative bacteria"
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Mansbach, Rachael Alexandra, Cesar Augusto Lopez Bautista, Nicolas W. Hengartner, and Sandrasegaram Gnanakaran. A Fragment Library for Drug Activity in Gram Negative Bacteria. Office of Scientific and Technical Information (OSTI), 2019. http://dx.doi.org/10.2172/1489938.
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Marteva-Proevska, Yulia, Tsvetan Velinov, Rumyana Markovska, Dilana Dobrikova, Liudmila Boyanova, and Ivan Mitov. High Level of Colistin Resistant Gram-negative Bacteria in a University Hospital in Bulgaria. "Prof. Marin Drinov" Publishing House of Bulgarian Academy of Sciences, 2021. http://dx.doi.org/10.7546/crabs.2021.06.12.
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Deng, Jinglan, Kexin Zhao, Qiuxia Zuo, et al. Risk factors for Multidrug-resistant Gram-negative bacteria in nosocomial infections: a meta-analysis. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, 2023. http://dx.doi.org/10.37766/inplasy2023.11.0045.
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Wang, Chuanhai, Deqing Yang, and Wentao Ni. Cefiderocol for the Treatment of Multidrug-Resistant Gram-Negative bacteria: A Systematic Review of Current Evidence. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, 2021. http://dx.doi.org/10.37766/inplasy2021.10.0063.
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Bezerra, Alexandre Sacchetti, Flavia Altheman Loureiro, Carla Maria Pasquareli Vazquez, Afonso Cesar Polimanti, and Rafi Felicio Bauab Dauar. Empiric Treatment of Foot Infection in Patients with Severe Diabetes. Science Repository, 2021. http://dx.doi.org/10.31487/j.jicoa.2021.04.04.
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Background: Despite being treated with antibiotics of broad spectrum recommended by International Consensus, severe diabetic patients with lower limb infection do not present a positive clinical evolution during empirical treatment. This study’s bacterial profile was analysed and compared with other worldwide hospital centers. Objective: To confirm the need of an individualized empirical treatment for severe diabetic patients with foot infection. Methods: Retrospective analysis of cultures and antibiograms of severe diabetic patients admitted by foot infection. Results: The results were consistent with the socioeconomic realities of developing countries. Gram-negative bacteria (52,11%) were present in most bone cultures. Results presented a high incidence of Enterococcus faecalis in both gram-positive (21,2%) and polymicrobial (34,7%) samples. Bacterial resistance with the use of ordinary antibiotics in the statistical analysis was high. Conclusion: The community infections should undergo broad spectrum empirical therapy combining amikacin (80,43%) or meropenem (72,00%) with gram-negative and vancomycin (100%) or teicoplanin (90,00%) or linezolid (74,19%) with gram-positive.
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Teeradakorn, Siriluk. Process development of succinic acid production from lignocellulosic materials by Actinobacillus sp. Chulalongkorn University, 2015. https://doi.org/10.58837/chula.res.2015.101.
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Total 30 samples were collected from soil and bovine dung in Surin (SR1-2), Suphanburi (SP1-10), Nakornsawan( NS1-12) and Nakhonprathom (NP1-6) province, Thailand. Two hundreds thirty bacterial isolates with succinic acid ability were obtained. Two hundreds and sixteen isolates were gram-positive and fourteen isolates were gram negative bacteria. Two of these negative isolates, isolate SP8/A4 and NS2/A2, have a potential for succinic acid production with 42.08 and 43.26 g/l, respectively. Actinobacillus succinogenes DSMZ 22257 was used as a representative for succinic acid production from lignocellulosic material. The use of 60 g/l (equivalent reducing sugar) sorghum straw hydrolyzate as a carbon source, longer lag phase was found and the highest amount cell growth of 2.665 g/l and succinic acid of 13.820 g/l were obtained. When using glucose 60g/l as a carbon source, a maximum cell growth of 3.185 g/l and succinic acid 44.799 g/l were obtained.
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Choudhary, Ruplal, Victor Rodov, Punit Kohli, John D. Haddock, and Samir Droby. Antimicrobial and antioxidant functionalized nanoparticles for enhancing food safety and quality: proof of concept. United States Department of Agriculture, 2012. http://dx.doi.org/10.32747/2012.7597912.bard.
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General concept. The reported 1-year study tested the feasibility ofpreparing antimicrobial and antioxidant nanoparticlesfunctionalized with natural phenolic compounds, as a first step to reach the ultimate goal - improving safely and quality of foods by developing novel antimicrobial and antioxidant food-contacting materials. The secondary objectives of the study were (a) selecting the most promising phenoliccompounds, (b) building nanoparticles with the selected phenolicgrafted on their Surface, and (c) testing antimicrobial and antioxidant properties of these particles. The study was expected to provide a " go/no go" decision as concerning the prospects of phenolic- bound nanoparticles as antimicrobial and antioxidant agents. Results. In course of the feasibility study, curucminwas chosen as the most promising phenoliccompound due to its high antibacterial activity exceeding other tested compounds by at leas one order of magnitude. Lipsome-typephospholipid/polydiacetylene(PDA) nanoparticlesfunctionalizedwith curcuminwere successfully built. The pitfall of limited curcumin amount that could be covalently bound to theparticle surface was circumvented by inclusion of curcunun in the liposome body. It was suggested onthe basis of fluorescence spectroscopy that curcuminwas bound by hydrophobic forces in the bi1ayer periphery of the Liposomesand therefore mightexert a contact effect on microorganisms. The curcumin functionalizednanoparticles(CFN) were shown to have a strong bactericidal activity towards both Gram-negative (E. coli) and Gram-positive (B. ce,·e11s) bacteria, but only limited effect against yeast. Furthermore, beyond the originallyplanned objectives, preliminary trials showed that CFN could be bound to silanized glass surface rendering aנבtiנnicrobial activity to the glass. Tnaddition, the particles showed antioxidantcapacity. Tberefore, it ,vas co11cluded tlוattlוeaims of tlוefeasibility study bad been successfully reached an
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Ramnaraine, Daveena. Beyond Antibiotics: Exploring the Antibacterial Mechanisms and Efficacy of Medicinal Plants and Endophytic Fungi. Florida International University, 2025. https://doi.org/10.25148/fiuurj.3.1.14.
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Due to the overuse of antibiotics, antibiotic resistance has become a global health crisis, and has forced an exploration of alternative antibacterial agents. This review explores natural solutions through the antibacterial potential of medicinal plants and their symbiotic endophytic fungi. Medicinal plants have been utilized for centuries to treat infections because of their rich phytochemical content, including alkaloids, flavonoids, and saponins, which exhibit antibacterial properties. Their efficacy is measured through minimum inhibitory concentration (MIC) assays, which showcase their ability to inhibit bacterial growth. Isolated compounds from medicinal plants demonstrate enhanced antibacterial activity by disrupting bacterial cell membranes, with MIC values as low as 3.0 µg/mL. However, challenges like inconsistent chemical composition and cultivation issues can limit the large-scale application of medicinal plants. Endophytic fungi, micro-fungi that reside in plant tissues, offer a promising alternative resulting from their ability to mimic the production of similar bioactive compounds. Their antibacterial activity is measured through agar well assays, and most strains inhibit both gram-positive and gram-negative bacterial growth demonstrated by zones of inhibition up to 34 mm. Unlike plants, endophytic fungi are easier to cultivate and can be optimized for mass production under controlled laboratory conditions, making them a sustainable source of novel antibiotics. By exploring the diverse chemical profiles of medicinal plants and endophytic fungi, this review demonstrates the potential of both to combat antibiotic-resistant bacteria effectively. Further research into their specific mechanisms and clinical trials is necessary to ensure their safety, but by advancing the exploration of these natural sources, they can contribute to the global effort to combat antibiotic resistance and revolutionizing the treatment of bacterial infections.
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Yedidia, I., H. Senderowitz, and A. O. Charkowski. Small molecule cocktails designed to impair virulence targets in soft rot Erwinias. United States-Israel Binational Agricultural Research and Development Fund, 2020. http://dx.doi.org/10.32747/2020.8134165.bard.
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Chemical signaling between beneficial or pathogenic bacteria and plants is a central factor in determining the outcome of plant-microbe interactions. Pectobacterium and Dickeya (soft rot Erwinias) are the major cause of soft rot, stem rot, and blackleg formed on potato and ornamentals, currently with no effective control. Our major aim was to establish and study specific bacterial genes/proteins as targets for anti-virulence compounds, by combining drug design tools and bioinformatics with experimental work. The approach allowed us to identify and test compounds (small molecules) that specifically interfere with the activities of these targets, by this impairing bacterial virulence. Two main targets were selected within the frame of the BARD project. The first is the ATP-binding cassette (ABC) transporters and methyl-accepting chemotaxis proteins (MCP) that have been characterized here for the first time in Pectobacteriaceae, and the second is the quorum sensing (QS) machinery of Pectobacterium with its major proteins and in particular, the AHL synthase ExpI that was identified as the preferred target for inhibition. Both systems are strongly associated with bacterial virulence and survival in planta. We found that Pectobacteriaceae, namely Dickeya and Pectobacterium, encode more ABC transporters and MCP in their genomes, compared to other bacteria in the order. For MCP, soft rot Pectobacteriaceae not only contain more than 30 MCP genes per strain, but also have more diverse ligand binding domains than other species in the Enterobacteriales. These findings suggest that both ABC transporters and MCP are important for soft rot Pectobacteriaceae pathogenicity. We now have a selection of mutants in these proteins that may be further explored to understand their direct involvement in virulence. In parallel, we studied the QS central proteins in pectobacteria, the signaling molecule N-acyl-homoserine lactone synthase, ExpI, and the response regulator ExpR, and established their phylogenetic relations within plant pathogenic Gram negative bacteria. Next, these proteins were used for virtual screening of millions of compounds in order to discover new compounds with potential to interfere with the QS machinery. Several natural compounds were tested for their interference with virulence related traits in Pectobacterium and their capability to minimize soft rot infections. Our findings using microcalorimetric binding studies have established for the first time direct interaction between the protein ExpI and two natural ligands, the plant hormone salicylic acid and the volatile compound carvacrol. These results supported a model by which plants interfere with bacterial communication through interkingdom signaling. The collaborative project yielded two research papers and a comprehensive review, which included new computational and bioinformatics data, in Annu. Rev. Phytopathol., the highest ranked journal in phytopathology. Additional two papers are in preparation. In order to transform the fundamental knowledge that have been gained during this collaborative BARD project into agricultural practice, to control soft rot bacteria, we have submitted a continual project.
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Coplin, David L., Shulamit Manulis, and Isaac Barash. roles Hrp-dependent effector proteins and hrp gene regulation as determinants of virulence and host-specificity in Erwinia stewartii and E. herbicola pvs. gypsophilae and betae. United States Department of Agriculture, 2005. http://dx.doi.org/10.32747/2005.7587216.bard.
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Gram-negative plant pathogenic bacteria employ specialized type-III secretion systems (TTSS) to deliver an arsenal of pathogenicity proteins directly into host cells. These secretion systems are encoded by hrp genes (for hypersensitive response and pathogenicity) and the effector proteins by so-called dsp or avr genes. The functions of effectors are to enable bacterial multiplication by damaging host cells and/or by blocking host defenses. We characterized essential hrp gene clusters in the Stewart's Wilt of maize pathogen, Pantoea stewartii subsp. stewartii (Pnss; formerly Erwinia stewartii) and the gall-forming bacterium, Pantoea agglomerans (formerly Erwinia herbicola) pvs. gypsophilae (Pag) and betae (Pab). We proposed that the virulence and host specificity of these pathogens is a function of a) the perception of specific host signals resulting in bacterial hrp gene expression and b) the action of specialized signal proteins (i.e. Hrp effectors) delivered into the plant cell. The specific objectives of the proposal were: 1) How is the expression of the hrp and effector genes regulated in response to host cell contact and the apoplastic environment? 2) What additional effector proteins are involved in pathogenicity? 3) Do the presently known Pantoea effector proteins enter host cells? 4) What host proteins interact with these effectors? We characterized the components of the hrp regulatory cascade (HrpXY ->7 HrpS ->7 HrpL ->7 hrp promoters), showed that they are conserved in both Pnss and Fag, and discovered that the regulation of the hrpS promoter (hrpSp) may be a key point in integrating apoplastic signals. We also analyzed the promoters recognized by HrpL and demonstrated the relationship between their composition and efficiency. Moreover, we showed that promoter strength can influence disease expression. In Pnss, we found that the HrpXY two-component signal system may sense the metabolic status of the bacterium and is required for full hrp gene expression in planta. In both species, acyl-homoserine lactone-mediated quorum sensing may also regulate epiphytic fitness and/or pathogenicity. A common Hrp effector protein, DspE/WtsE, is conserved and required for virulence of both species. When introduced into corn cells, Pnss WtsE protein caused water-soaked lesions. In other plants, it either caused cell death or acted as an Avr determinant. Using a yeast- two-hybrid system, WtsE was shown to interact with a number of maize signal transduction proteins that are likely to have roles in either programmed cell death or disease resistance. In Pag and Pab, we have characterized the effector proteins HsvG, HsvB and PthG. HsvG and HsvB are homologous proteins that determine host specificity of Pag and Pab on gypsophila and beet, respectively. Both possess a transcriptional activation domain that functions in yeast. PthG was found to act as an Avr determinant on multiple beet species, but was required for virulence on gypsophila. In addition, we demonstrated that PthG acts within the host cell. Additional effector genes have been characterized on the pathogenicity plasmid, pPATHₚₐg, in Pag. A screen for HrpL- regulated genes in Pnsspointed up 18 candidate effector proteins and four of these were required for full virulence. It is now well established that the virulence of Gram-negative plant pathogenic bacteria is governed by Hrp-dependent effector proteins. However; the mode of action of many effectors is still unresolved. This BARD supported research will significantly contribute to the understanding of how Hrp effectors operate in Pantoea spp. and how they control host specificity and affect symptom production. This may lead to novel approaches for genetically engineering plants resistant to a wide range of bacterial pathogens by inactivating the Hrp effectors with "plantabodies" or modifying their receptors, thereby blocking the induction of the susceptible response. Alternatively, innovative technologies could be used to interfere with the Hrp regulatory cascade by blocking a critical step or mimicking plant or quorum sensing signals.