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1
Vieira, Mónica Andreia Almeida. "Monitoring antibiotics in the environment. Study of Quinoxaline derivatives bioactivity." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/11350.
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Dissertação para obtenção do Grau de Doutor em
Química Sustentável<br>Antimicrobial agents have revolutionized medicine and promoted an increase in average life expectancy of human populations worldwide. These drugs are used not only in human medicine but also in veterinary practice, in the treatment and prevention of infections, and in some regions in the world, as well as growth promoters, ensuring a greater and better animal production. The use of antimicrobial agents in animal production causes contamination of the final product with drug residues that are eventually distributed in human food chain. Residues of antimicrobial agents provenient from human and animal consumption are also present in sewage, surface water or ground water. It is still unknown all the consequences of this contamination, but there are indications of changes in indigenous microbiota. The use of these drugs was quickly followed by the emergence of resistance, which led to decreased efficacy and compounds available. Therefore, the spread of antimicrobial agents in the environment is also associated with increased resistance to such drugs.
The presented work intended to establish methods for monitoring the presence of antibiotics in animal foods, evaluate if the presence of antimicrobial agents in the
environment at sub-inhibitory concentrations can contribute to the selection of resistant bacteria and characterize the biological activity of a number of compounds of the quinoxaline family as potential new antimicrobial agents.
In order to achieve these objectives, chromatographic techniques were used for
detection and quantification of antimicrobial agents, methods of microbiology and molecular biology to evaluate the behavior of bacteria under selective pressure.
Various strains of prokaryotes and eukaryotes microorganisms were also used to
evaluate the antimicrobial activity of N-oxide derivatives of quinoxaline. We used,
also, cell cultures to assess the potential toxicity of these new antibiotics. A new
chromatographic method was developed to quantify the reduced and oxidized forms
of glutathione, in order to infer the cellular oxidative stress induced by exposure to the quinoxaline derivative compounds with proven antimicrobial activity.
The results confirm that the chromatographic HPLC-DAD methods are powerful tools in monitoring food quality. They also indicate that the presence of subinhibitory amounts of ciprofloxacin in water may influence the dynamic of susceptible and resistant to ciprofloxacin Escherichia coli population. An assessment of the biological activity of quinoxaline derivatives indicated the
compounds studied as potential new antimicrobial agents who have shown low
toxicity in cell lines and oxidative cell damage in small extent.<br>Fundação para a Ciência e Tecnologia - bolsa de doutoramento SFRH / BD /48116 / 2008
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Parr, J. A. "Antimicrobial properties of silicone quaternary ammonium compounds." Thesis, Bucks New University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375600.
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Trienekens, Theodora Antoinetta Maria. "Urinary tract infections and antimicrobial agents A study into factors influencing the efficacy of antimicrobial agents /." Maastricht : Maastricht : Rijksuniversiteit Limburg ; University Library, Maastricht University [Host], 1993. http://arno.unimaas.nl/show.cgi?fid=5757.
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Muppalla, Kirankirti. "Functionalization of Resorcinarenes and Study of Antimicrobial Activity." Scholar Commons, 2001. http://scholarcommons.usf.edu/etd/3824.
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Cavitands are very important class of compounds in supramolecular chemistry. These molecules contain rigid enforced cavity,and have attracted considerable attention in supramolecular chemistry as building blocks for the construction of carcerands, hemicarcerands, and other host guests complexes. Nearly 40 years ago, Niederl and Vogel laid foundation for the study of such type of condensation reactions. In our laboratory we are involved in synthesis of resorcinarenes with readily available substrates such as resorcinol and aldehydes to form a cyclic tetramer.
Herein, I present detailed studies about the functionalization of the synthesized tetramers and their antimicrobial activity. Octahydroxy resorcinarenes were synthesized and perallylated which served as acyclic diene precursors for ring closing metathesis reaction. Studies were carried out to see effect of C-2 substituent of resorcinol and effect of aryl substituents, and aliphatic substituents on ring closing metathesis. This thesis describes the synthesis of bridged resorcinarenes and study of antimicrobial activity of resorcinarenes.
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Shaker, L. A. "Effect of chlorohexidine on bacterial spores." Thesis, Cardiff University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381226.
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Mather, Alison Elizabeth. "Epidemiological and ecological approaches to the study of antimicrobial resistance." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2624/.
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To date, investigation and policy development relating to antimicrobial resistance (AMR) have focused largely on describing patterns of resistance to individual antimicrobials, often from restricted data sources. What this approach fails to accommodate is the complexity of AMR, such as genetic linkage of resistance determinants, which could potentially lead to inaccurate inference. Novel approaches are therefore required to bring new perspectives on the epidemiology of AMR. These studies take an ecological perspective of AMR, examining several key issues: The relative contribution to AMR from animal and human populations; the potential differences between passive and active surveillance of AMR; the associations of age, antimicrobial treatment and a shared environment with AMR diversity; the relationships between AMR phenotype and genotype; and exploring the additional information provided by DNA sequencing data. Novel ecological and epidemiological approaches were developed to examine long-term passive surveillance data of AMR in Salmonella Typhimurium DT104 (DT104) isolates from concurrently sampled and sympatric human and animal populations in Scotland. By examining the diversity and the phenotypic and temporal relatedness of the resistance profiles, the most likely source of resistance was assessed. The conclusions were that whilst ecologically connected, animals and humans have distinguishable DT104 communities, differing in prevalence, linkage, and diversity. Furthermore, the sympatric animal population is unlikely to be the major source of resistance for human DT104. As robust data are critical to any analysis, the potential differences between data collected by different surveillance types were examined. These systems are not generally designed to detect emerging resistances. The diversity of phenotypic AMR from passive and active surveillance data of poultry Salmonella Heidelberg and swine Salmonella Typhimurium var. 5- isolates derived from animals and foods-of-animal origin were contrasted to assess their suitability for detecting emerging resistance patterns. Results indicated that active and passive surveillance approaches were potentially sampling from distinguishable microbiological communities and are therefore complementary, and that passive surveillance is better at detecting rare profiles. The ecological and epidemiological approach was also applied to a different organism, in a different ecosystem. In order to assess the association of age and antimicrobial exposure with AMR diversity, E. coli from cows and calves on seven dairy farms were examined. There were distinguishable populations of resistance phenotypes on the farms, associated with both age and treatment. Multivariable models were developed to examine simultaneously the association of age, treatment, time, and farm with AMR diversity. These results indicated that there may be particular animal husbandry or farm management practices which influence AMR diversity, and which appear to be different for co-habiting young and adult dairy cattle. The majority of AMR data collected by surveillance systems are phenotypic in nature. However, it is often the underlying genotype that is of interest, which until now could only be achieved with the application of molecular methods. A novel latent class Bayesian model was developed to infer the prevalence of various AMR determinants in a population given a sample of phenotypes, which was applied to animal and human DT104 data. Differences were demonstrated in the estimated prevalences of a number of AMR determinants between the two populations, further supporting the previous observations that the epidemiologies of the organism, the resistance determinants, or both, are distinguishable. To obtain a greater resolution with which to compare AMR in different populations, a second-generation sequencing platform was used to obtain DNA sequencing data from select animal and human DT104 isolates. The objectives were to determine the diversity of the bacteria and of the resistance determinants. Whilst analysis of the resistance determinants is ongoing, preliminary results have suggested that the subtypes of DT104 infecting animals and humans are indeed similar. Overall, these studies comprise application of novel methods and frameworks for the analysis of AMR. The implication of these studies is that greater and more explicit thought is needed regarding the design, collection, analysis, and interpretation of AMR data properly to inform policy.
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He, Jing. "Design and Study of Novel Antimicrobial Peptides with Proline Substitution." Ohio University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1257779581.
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Qian, Lei. "A study of N-halamine structures in regenerable antimicrobial textiles /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
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Morgan, Thomas Daniel. "Aspects of oral care and antimicrobial efficacy : a microcalorimetric study." Thesis, University of Kent, 1997. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507958.
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Daham, S. A. "The antibacterial activity of chlorhexidine in combination with dodecyl trimethyl ammonium bromide and some other antimicrobial agents." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378115.
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Yaeger, Eileen M. "Quantitative Study of Clostridium difficile Incidence Related to Influenza and Antimicrobial Use." ScholarWorks, 2015. https://scholarworks.waldenu.edu/dissertations/614.
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In the United States, influenza causes approximately 36,000 deaths and over 200,000 hospitalizations each year with elderly most often affected. Clostridium difficile infection (CDI) is another major health care challenge and pressing public health issue associated with 14,000 deaths and over 335,000 hospitalizations annually. The use of antibiotics has been implicated in the development of CDI. This study's purpose was to test the relationship of seasonal influenza incidence and antiviral/antibiotic use in CDI development among hospitalized patients. Grounded in the epidemiologic wheel model of man-environment interactions, this retrospective observational study described and analyzed data from a proprietary, laboratory, and pharmacy-based system from a cohort of hospitals. The association between 147 patients with a diagnosis and/or positive test for influenza, the independent variables of delivery of antivirals/antibiotics (n = 130) during the patient's hospitalization, and the dependent variable of positive test or diagnosis of CDI (n = 17) was tested using multiple logistic regressions. The study results did not prove to be significant for the 3 research questions, suggesting no impact of antiviral use (R2 = .05, p = .336), antibiotic use (R2 = .05, p = .290), or antiviral and/or antibiotic use (R2 = .04, p = .382) on development of CDI within 60 days of discharge. However, findings indicated that recommended antiviral medication was inconsistently administered to influenza positive patients and that inappropriate prescribing patterns for antimicrobial agents coincided with seasonal influenza. Implications for positive social change include confirming the importance of antibiotic stewardship as an essential aspect of quality healthcare.
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Wan, Yang. "Synthesis of β,γ-diamino acids and their use to design new analogues of the antimicrobial peptide Gramicidin Septide antimicrobien, la Gramicidine S". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS407/document.
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Dans notre groupe, nous nous intéressons au développement de peptides contenant des acides γ-aminés. Comme d’autres peptides contenant des acides aminés non naturels, ils ont montré leur capacité à posséder des conformations stables et/ou des propriétés biologiques intéressantes. De plus, ces peptides sont généralement résistant à la protéolyse. Dans l’objectif de synthétiser des acides -diaminés sous la forme d’un seul stéréoisomère, nous avons développé une voie de synthèse reposant sur une réaction de Blaise suivie d’une réduction diastéréosélective. En appliquant cette méthode, nous avons synthétisé des acides β,γ-diaminés dérivés de la D-phénylalanine et de l’acide L-glutamique. Le premier a été utilisé pour concevoir des analogues d’un peptide antimicrobien, la gramicidine S. Comparé à la molécule parent, les analogues ont montré une cytotoxicité beaucoup moins importante pour les cellules hôtes tout en conservant une activité antibactérienne intéressante. Cette étude nous a donné de meilleures connaissances pour développer d’autres analogues de la gramicidine S ainsi que d’autres peptides antimicrobiens. Nous avons également effectué de nombreuses optimisations pour synthétiser de façon efficace des acides β,γ-diaminés cycliques à partir de l’acide L-glutamique. Les oligomères incorporant ces acides β,γ-diaminés et des acides α-aminés ont montré un fort potentiel pour l’adoption de conformations stables. Ces études vont être poursuivies<br>In our group, we are interested in developing peptides containing β,γ-diamino acids . Along with many other peptides containing unnatural amino acids, they have shown the ability to possess stable conformations and/or interesting biological activities. Moreover, those peptides are usually more resistant to proteolysis. In order to synthesize stereopure γ-amino acids, we have developed a synthetic route using Blaise reaction and subsequent diastereoselective reduction as key reactions. Through applying this method, we have synthesized β,γ-diamino acids derived from D-phenylalanine and L-glutamic acid. The former β,γ-diamino acid was used for designing antimicrobial peptide gramicidin S analogues. Compared with mother molecule, the analogues exerted much less host cell cytotoxicity while remaining interesting antibacterial activity. Meanwhile, it gave us more knowledge for further developing analogues of gramicidin S as well as other antimicrobial peptides. We also paid lots of effort to efficiently synthesize cyclic β,γ-diamino acids starting from L-glutamic acid. Interestingly, when oligomers incorporating this β,γ-diamino acids and α-amino acids, they have shown the potential to adopt stable conformations. The following studies will be continuously investigated
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Freshwater, Julie L. "Impact of Antimicrobial Use on the Resistance of Pseudomonas aeruginosa in the Intensive Care Unit Setting in a Large Academic Medical Center." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275443984.
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Cassin, Margaret Emily. "The Design of Antimicrobial Detachable Thin Films for the Study of Hepatic Infections." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/77426.
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Microbial infections are a global problem. Due to the over and misuse of antibiotics, drug-resistant pathogens are becoming more common. It is imperative to explore broad spectrum antimicrobial approaches. In this work, we modified collagen/hyaluronic acid polyelectrolyte multilayers (PEMs) with the natural antimicrobial peptide, LL-37 to study hepatic infections. LL-37 was physisorbed and covalently linked to the surface of the PEMs. Escherichia coli DH10B were cultured in the presence of LL-37modified PEMs in bacterial adhesion and contact killing models. Physisorbed LL-37 PEMs prevented bacterial adhesion and could also kill pathogens in the surrounding environment due to the release of LL-37 from the film. Immobilized LL-37 PEMs resulted in less bacterial adhesion on the surface due to the presence of the peptide. Films were then placed in contact with primary rat hepatocytes as well as in hepatocyte/bacteria co-cultures. LL-37 input concentrations up to of 16μM did not exhibit cytotoxic effects on hepatocytes. The LL-37 modified PEMs exhibited a hepatoprotective effect on albumin and urea secretion functions in co-cultures. The hepatoprotective effects were dependent on the ratio of hepatocytes and bacteria as well as the concentration of LL-37. These findings are encouraging and demonstrate that LL-37 modified PEMs can be used to investigate hepatic infections caused by bacteria.<br>Master of Science
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Grau, Campistany Ariadna. "Design, synthesis and study of the biological and biophysical activity of antimicrobial peptides." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/279307.
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The global emergence and spread of multidrug-resistant bacteria is an important public health issue. However, the antimicrobial pipeline remains unacceptably lean, in fact over the last 25 years, the number of antimicrobial agents that reach the market has sharply decreased. In this context, there is now a renewed interest in the search for drugs that have more than one target on the bacterial cell, rather than a specific chiral receptor or enzyme. Antimicrobial peptides (AMPs) are a class of antibiotics that have attracted great interest in the last few years because they rarely spur the development of resistant organisms as their mechanism of action involves disruption of the bacterial membrane.
In this thesis we report the design, preparation and activity of new compounds based on the sequence of the polymyxins, a class of antibiotics highly active against Gramnegative bacteria, and used clinically as last resort treatment for multidrug-resistant pathogens. The compounds synthesized proved to be highly active against both Grampositive and Gram-negative bacteria, including several strains of resistant bacteria. Furthermore, biophysical experiments using liposomes and monolayers as model membranes and flow cytometry and transmission electron microscopy using bacteria were carried out to study the mechanism of action of these compounds. The results of the most active candidate indicate that an alternative, non-membrane dependent mechanism of action might be involved.
In the second part of the thesis, a series of 9 peptides were designed and synthesized from repeated KIAGKIA motifs, based in the sequence of the antimicrobial peptide PGLa from the magainin family, with lengths between 14 and 28 amino acids. Circular dichroism spectroscopy showed that they all formed alpha-helices when found in a lipid environment. Biological assays for haemolysis and antimicrobial activity, as well as fluorescence vesicle leakage and solid-state NMR spectroscopy, were used to correlate peptide length with membrane activity. These data are fully consistent with the formation of transmembrane pores. Only peptides that are long enough to span the hydrophobic bilayer core can induce vesicle leakage, haemolysis, and inhibit bacterial growth. The shorter peptides do not show these effects. Solid-state NMR analysis in oriented bilayers with different thickness also demonstrated the need for a minimum peptide length to flip from a surface-bound alignment into a more inserted, possibly even transmembrane state. With increasing length the peptides start to tilt and perturb the bilayer. Since the threshold behaviour seen for biological activity closely matches the biophysical results, the peptides could be used as molecular rulers to determine the thickness of bacterial membranes, showing that E. coli (≈ 27 Å) < S. aureus and P. aeruginosa (≈ 30 Å) < E. faecalis (≈ 34 Å).<br>L'aparició i propagació mundial de bacteris resistents a múltiples fàrmacs s’ha convertit en un problema clínic molt important. No obstant això, el nombre de nous antimicrobians que es troben en les últimes etapes de desenvolupament és molt baix. Els pèptids antimicrobians són una classe d’antibiòtics que han despertat gran interès en els últims anys pel fet que poques vegades estimulen el desenvolupament d’organismes genèticament resistents ja que la seva diana terapèutica és principalment la membrana bacteriana.
En aquesta tesi es descriu el disseny, preparació i activitat de nous compostos basats en la seqüència de les polimixines, un tipus de pèptids antimicrobians altament potents contra bacteris Gram-negatius i usats clínicament. Els compostos sintetitzats van presentar elevada activitat tant en bacteris Gram positius com Gram-negatius, incloent diverses soques resistents. Addicionalment, experiments biofísics usant liposomes i monocapes com a models de membrana i citometria de flux i microscòpia electrònica de transmissió usant bacteris es van usar per estudiar el mecanisme d’acció d’aquests compostos. Els resultats del candidat més actiu semblen indicar que presenta un mecanisme d’acció alternatiu on la membrana bacteriana no és l’única diana terapèutica.
En la segona part de la tesi, es descriu el disseny i síntesi d’una sèrie de 9 pèptids, basats en la seqüència del pèptid antimicrobià PGLa de la família de les magainines. Els pèptids alfa-helicoïdals (vist mitjançant l’ús de dicroïsme circular), presenten repeticions del heptàmer KIAGKIA, amb llargades de 14 a 28 aminoàcids. Assaigs biològics, de fluorescència i de RMN de fases condensades es van usar per relacionar la llargada peptídica amb la activitat en la membrana. Les dades obtingudes són consistents amb la formació de porus transmembrana, només aquells pèptids prou llargs per travessar la bicapa lipídica indueixen permeabilització, hemòlisi i inhibeixen el creixement bacterià mentre que els pèptids curts no mostren aquests efectes. L’anàlisi usant RMN de fases condensades amb lípids de diferent llargada també va mostrar la necessitat d’una llargada mínima dels pèptids per passar d’un estat superficial a un estat més inserit, probablement transmembrana. Atès que els llindars observats per a l'activitat biològica coincideixen estretament amb els resultats biofísics, els pèptids van ser utilitzats com a regles moleculars per determinar el gruix de les membranes bacterianes, és a dir E. coli (≈ 27 Å) < S. aureus i P. aeruginosa (≈ 30 Å) < E. faecalis (≈ 34 Å).
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Marques, ClaÌudia Nogueira Hora. "Use of Pseudomonas aeruginosa expressing Lux genes to study antimicrobial susceptibility of biofilms." Thesis, University of the West of England, Bristol, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411964.
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Liu, Yang Li Men`gshi. "Study of antimicrobial activity and mechanism of zinc oxide nanoparticles against foodborne pathogens." Diss., Columbia, Mo. : University of Missouri-Columbia, 2009. http://hdl.handle.net/10355/6718.
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The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on March 23, 2010). Thesis advisor: Dr. Mengshi Lin. Includes bibliographical references.
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Pelissari, Grace Priscila [UNESP]. "Estudo farmacognóstico e avaliação das atividades antibacteriana e imunomoduladora de Melampodium divaricatum (Rich. In Pers) DC. (Asteraceae)." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/91685.
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pelissari_gp_me_arafcf.pdf: 3328486 bytes, checksum: eca10418295f68f0485506997b0e2f5b (MD5)<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)<br>Universidade Estadual Paulista (UNESP)<br>Diante do amplo uso popular da espécie Melampodium divaricatum (Rich. In Pers.) DC (Asteraceae) conhecida no Brasil como falsa-calêndula, fica evidente o provável potencial farmacológico desta espécie justificando assim estudos que possam confirmar suas atividades biológicas bem como aspectos que garantam a qualidade e segurança de seu uso pela população. Neste trabalho foram estudados os extratos aquosos, etanólicos e o óleo essencial obtido a partir das partes aéreas desta espécie buscando avaliar possíveis atividades biológicas, bem como o estudo de parâmetros farmacognósticos relacionados à qualidade do material vegetal em estudo. Avaliou-se o efeito destes extrativos no sistema imunológico murino, utilizando cultura de macrófagos peritoneais de camundongos Swiss e também a atividade antimicrobiana pela metodologia de difusão em ágar frente às bactérias Gram-positivas: Staphylococcus aureus e Bacillus subtilis e Gram-negativas: Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Shigella sonnei, Serratia marcescens. O estudo farmacognóstico foi realizado através de ensaios físico-químicos, qualitativos e quantitativos. Os resultados indicam que o material vegetal encontra-se dentro dos padrões de qualidade estabelecidos para materiais vegetais em geral. Os componentes majoritários presentes no óleo essencial, trans-cariofileno (48,6%); germacreno-D (13,2%); biciclogermacreno (10,6%); óxido de cariofileno (3,0%) e α-humuleno (2,2%) não apresentam variações estatisticamente significativas quando obtidos do material vegetal seco e fresco. Em triagem fitoquímica das partes aéreas foi caracterizada a presença de flavonóides e triterpenos e através de doseamento verificou-se que o extrato etanólico 99,5% apresentou um maior teor de flavonóides totais.<br>According the ample popular use of the Melampodium divaricatum (Rich. In Pers.) DC (Asteraceae) known in Brazil as false-calendula, it is evident the pharmacological potential of this species which justify studies that confirm its biological activities and aspects that guarantee the quality and safety of its use for the population. In this work the aqueous and ethanolic extracts as well as the essential oil from the aerial parts of this species had been studied in order to evaluate possible biological activities, as well as the study of related pharmacognostic parameters to the quality of the plant. It was evaluated the effect of these extractives in murine imunne system, using peritoneal macrophages cultures from Swiss mice and also the antimicrobial activity for the methodology of agar diffusion to Gram-positive bacteria: Staphylococcus aureus and Bacillus subtilis and Gram-negatives: Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Shigella sonnei, Serratia marcescens. The pharmacognostic study was carried through qualitative and quantitative assays physicochemical. The results indicate that the vegetal material was according to established standards of quality established for plant drugs in general. The majority components present in the essential oil trans-caryophyllene (48.6%); germacrene-D (13.2%); bicyclogermacrene (10.6%); caryophyllene oxide (3.0%), α-humulene (2.2%), do not present statiscally significant variations when obtained from dry or fresh plant. In phytochemistry analysis of the aerial parts the presence of flavonoids and triterpenoids was characterized and through dosage was verified that the ethanolic extract presented higher level of total flavonoids. As extracts as essential oils presented immunomodulatory activity to the murine macrophages, inhibiting powerfully the production of NO and H2O2 in a form dose-dependent.
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Ng'uni, Tiza Lucy. "Medicinal uses of Galenia africana: A study of the antimicrobial, antifungal and anticancer properties." University of the Western Cape, 2017. http://hdl.handle.net/11394/5670.
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Philosophiae Doctor - PhD<br>Over the years, microorganisms have become resistant to commonly used antimicrobial agents
leading to multidrug resistance. This is believed to occur even with new classes of therapeutic
agents thus creating a challenge on the global healthcare system. The study of medicinal plants
allows for their possible use as alternative therapeutic agents. Galenia africana (G. africana) is a
South African medicinal plant with numerous health benefits.
The purpose of this study was to evaluate the potential antimicrobial, antifungal and anticancer
properties of the ethanolic extract of G. africana. Prior to evaluating these properties, in vitro and
in vivo acute toxicity studies were conducted to assess the toxicity profile of G. africana.
The toxicity profile of the G. africana extract was evaluated using acute toxicity studies
conducted in animal and reconstituted human epidermis skin models. The results of the acute
oral and dermal toxicity studies revealed that the median lethal dosage (LD50) for G. africana
extract in Sprague-Dawley rats was considered to exceed 2000 mg/kg. In the dermal sensitization
study, the stimulation index (SI) values for the mice treated with the G. africana extract at
concentrations of 25% (50 mg/ml), 50% (100 mg/ml), and 100% (200 mg/ml), when compared
to the control group, were 1.3, 0.9 and 1.3, respectively which did not result in an SI value of ? 3
in any group. Hence, it did not elicit a hypersensitivity response. In the irritation test, the G.
africana (concentrate) and G. africana (in-use dilution) extracts were non-irritant on the
reconstituted human epidermis.
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Nguni, Tiza. "Medicinal uses of Galenia africana: A study of the antimicrobial, antifungal and anticancer properties." University of the Western Cape, 2018. http://hdl.handle.net/11394/6608.
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Magister Scientiae - MSc (Medical BioSciences)<br>Medicinal uses of Galenia africana: A study of the antimicrobial, antifungal and anticancer properties
Over the years, microorganisms have become resistant to commonly used antimicrobial agents leading to multidrug resistance. This is believed to occur even with new classes of therapeutic agents thus creating a challenge on the global healthcare system. The study of medicinal plants allows for their possible use as alternative therapeutic agents. Galenia africana (G. africana) is a South African medicinal plant with numerous health benefits.
The purpose of this study was to evaluate the potential antimicrobial, antifungal and anticancer properties of the ethanolic extract of G. africana. Prior to evaluating these properties, in vitro and in vivo acute toxicity studies were conducted to assess the toxicity profile of G. africana.
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Abutheraa, Nouf. "Antimicrobial stewardship in the management of sepsis in maternity hospitals : a mixed methodology study." Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30289.
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Background: Sepsis is one of the leading causes of maternal mortality and morbidity. The absence of a clear diagnostic marker challenges the process of starting antibiotic therapy. Early identification and management of sepsis is essential. Thus, the sepsis six care bundle (SSCB) was introduced in the UK to improve the care of sepsis patients. Aim: To evaluate assessment of sepsis and subsequent management including the antibiotic therapy prescribed, and to use this data as a basis of antimicrobial stewardship programme (AMSP) and quality improvement plan within maternity units. Methods: This study was conducted within three maternity units of NHS Greater Glasgow & Clyde using a mixed methodological approach of an initial quantitative study supplemented by a qualitative study, followed by a quality improvement for further service improvement. Results: Sepsis was diagnosed in 3% (n=89/2690) of women. There was an inconsistent clinical application of SIRS criteria to inform diagnosis. No causative pathogen was isolated from 60% of clinical specimens. Antibiotic therapy was justified in only 31 women with positive culture results. There was a limited application of AMSPs in the maternity units and midwives did not make a positive contribution, and had a low clinical threshold for initiating therapy. Only 37.1% of the 89 women diagnosed with sepsis had the identifiable SSCB sticker prominently displayed on their medical notes. Interview findings indicate that this resulted from the absence of implementation strategies, the challenge of diagnosing sepsis and sub-optimal evaluation and review of patients post-diagnosis. Conclusion: A specialized SSCB specifically for the obstetric population with the full contribution of the multidisciplinary team needs to be developed. Given midwives' central involvement in initial diagnosis, ongoing patient monitoring and antibiotic administration, a more midwife-centred approach to reviewing treatment is a promising way to develop AMSPs in maternity wards.
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Jacob, Rebecca. "Lipid bilayers and their interactions with the antimicrobial peptide LL37: a TIR Raman study." Thesis, KTH, Skolan för kemivetenskap (CHE), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207018.
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As a direct consequence of the misuse of antibiotics since its first discovery, bacteria have developed extensive resistance mechanisms making them once again potential lethal threats. This eventuality has triggered a vast research effort from scientists worldwide to find solutions to mitigate antimicrobial resistance. One such option is the identification of new potential antimicrobial agents, like for example antimicrobial peptides (AMPs). Various methods have been applied to evaluate the properties and determine the complex mechanism of AMPs. However, the details of the mechanism remain unknown and hence the work in this project seeks to examine the suitability of using TIR Raman, a vibrational spectroscopy technique which is sufficiently surface sensitive to study the interaction of AMPs in contact with lipid bilayers, which are just a few nanometres thick. In order to evaluate the information that could be extracted from TIR Raman, measurement of solid supported lipid bilayers in the absence of peptides were first carried out. In particular, the lipid DMPC with a phase transition close to room temperature, was measured at various temperatures to determine spectral changes associated with the transition. For the peptide-membrane interactions, the AMP LL37 was put into contact with solid supported lipid bilayers modelling the cell membranes of bacteria (DOPE, DOPG) or humans (DOPC) respectively. The data clearly indicates that the membrane composition, and specifically the lipid head group charge, play an important role in the peptide-membrane interactions. In the bilayers mimicking bacteria cell membranes, the peptide either absorbed onto or inserted into the bilayer. In contrast, for the bilayer modelling a human cell membrane, no significant variations were detected, indicating no interaction with LL37. The findings presented in this work generally coincide with similar research of LL37 using other techniques. At hand of the herein presented data, TIR Raman has proven suitable and effective in detecting effects of antimicrobial peptides in contact with model lipid bilayers, and hence can be recommended for further studies.<br>Som en direkt följd av missbruket av antibiotika sedan det först upptäcktes, har bakterier utvecklat omfattande resistensmekanismer vilket föranlett dem att återigen utgöra potentiellt dödlig hot. Denna situation har manat fram en väsentlig forskningsinsats från forskare världen över att hitta lösningar för att minska antimikrobiell resistens. Ett sådant alternativ har varit identifieringen av nya potentiella antimikrobiella substanser, så som till exempel antimikrobiella peptider. Ett flertal metoder har använts för att både evaluera peptiders egenskaper och fastställa deras komplexa mekanism. Detta till trots förblir de exakta detaljerna i mekanismen okända, vilket föranlett arbetet i detta projekt att undersöka lämpligheten i att använda TIR Raman, en vibrational-spektroskopisk metod som är tillräckligt ytkänslig för att studera interaktionen hos antimikrobiella peptider i kontakt med lipidmembran, vilka endast är några få nanometer tjocka. För att evaluera informationen som kan utvinnas med TIR Raman, utfördes först mätningar av lipidmembran, skapade på ett solitt underlag, utan tillägg av peptider. Mer noggrant, har lipiden DMPC med en fasövergång nära vid rumstemperatur, mätts vid olika temperaturer för att fastställa spektrala variationer associerade till övergången. För peptid-membran interaktionerna, sattes den antimikrobiella peptiden LL37 i kontakt med lipidmembran som modellerar cellmembranet hos bakterier (DOPE, DOPG) respektive människor (DOPC). Mätdatan indikerar tydligt att membrankompositionen, och där specifikt laddningen av lipidens huvudgrupp, spelar en viktig roll i membran-peptid interaktionerna. För lipidmembranen som imiterar bakteriella cellmembran, adsorberade peptiden till membranet eller integrerades in i det. Till skillnad från detta, kunde inga signifikanta variationer detekteras för lipidmembranet som modellerade ett mänskligt membran vilket indikerar att det inte interagerar med peptiden LL37. Upptäckterna som presenteras i detta arbete sammanfaller generellt med andra, liknande studier där andra instrument använts för att undersöka LL37. Det kan ur materialet som presenterats här utläsas att TIR Raman visat sig lämpligt och effektivt i detekteringen av antimikrobiella peptider i kontakt med modeller av lipidmembran, och kan därav rekommenderas för fortsatta studier.
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Boukherissa, Amira. "Study ot the coevolution between antimicrobial peptides and peptide transporters in legume-rhizobium symbiosis." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASB043.
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Les légumineuses présentant une carence en azote peuvent entrer en interaction symbiotique avec des bactéries du sol fixatrices de N₂ appelées rhizobia. Dans cinq clades de légumineuses, une stratégie d’exploitation appelée différenciation terminale des bactéroïdes (TBD) a évolué dans laquelle les rhizobiums subissent une différenciation extrême. Les bactéries terminalement différenciées sont plus grandes, polyploïdes, ont une membrane perméabilisée, et sont meilleures à la fixation de N₂, fournissant un retour sur investissement plus élevé pour la plante. Nous savons que dans deux clades, IRLC (par exemple, Medicago spp.) et Dalbergioïds (par exemple, Aeschynomene spp.), ce processus de différenciation est déclenché par un ensemble de peptides antimicrobiens végétaux apparemment non apparentés avec une activité antimicrobienne à la membrane connue sous le nom de peptides Nodule-spécifiques Cystéine-Riche (NCR). À son tour, les rhizobia exposés au stress provoqué par les NCRs nécessitent un transporteur de peptides ABC de la famille BacA pour faire face à ce stress. Cependant, si des peptides NCR ou des peptides similaires sont également trouvés dans d’autres clades où la TBD se produit et la relation évolutive entre ces peptides reste inconnue. Dans ce projet, nous avons testé l’hypothèse d’une coévolution convergente entre les différents clades de légumineuses et leur rhizobia engagés dans ce programme de différenciation, tant au niveau phénotypique que moléculaire. Pour ce faire, nous avons combiné des analyses d’évolution moléculaire avec des tests fonctionnels, fournissant ainsi des connaissances expérimentales sur la question fondamentale de la contingence et de répétabilité en évolution tout en générant simultanément de nouveaux outils pour concevoir une symbiose plus efficace<br>Legume plants under nitrogen deficiency can enter a symbiotic interaction with N₂-fixing soil bacteria called rhizobia. In five legume clades, an exploitive strategy called Terminal Bacteroid Differentiation (TBD) has evolved in which rhizobia undergo extreme differentiation. Terminally differentiated bacteria are larger, polyploid, have a permeabilized membrane, and are better at N₂ fixation, providing a higher return on investment for the plant. We know that in several members of the distantly related Inverted Repeat Lacking Clade (IRLC, e.g., Medicago spp.) and the Dalbergioid clade (e.g., Aeschynomene spp.), this differentiation process is triggered by a set of apparently unrelated plant antimicrobial peptides with membrane damaging activity known as Nodule-specific Cysteine-Rich (NCR) peptides. In turn, rhizobia exposed to NCR stress requires an ABC peptide transporter of the BacA family to cope with this stress. However, whether NCR peptides or similar peptides are also found in other clades where this occurs and the evolutionary relation among these peptides remains unknown. In this project, we tested whether NCR peptides and BacA peptide transporters evolved independently in the different legume clades that induce TBD and their rhizobia, implying convergent coevolution, both at phenotypic and molecular levels. We combined molecular evolution analyses with functional assays, thus providing experimentally informed knowledge on the fundamental question of the part of contingency and repeatability in evolution while simultaneously generating new tools to engineer a more efficient symbiosis
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Carr, Matthew. "Advancing our understanding of lipid bilayer interactions : a molecular dynamics study." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/16148.
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In recent years, advances in computer architecture and lipid force field parameters have made Molecular Dynamics (MD) a powerful tool for gaining atomistic resolution of biological membranes on timescales that other tools simply cannot explore. With many key biological processes involving membranes occurring on the nanosecond timescale, MD allows us to probe the dynamics and energetics of these interactions in molecular detail. Specifically, we can observe the interactions taking place as a peptide or protein comes into contact with a lipid bilayer, and how this may shape or alter the bilayer either locally (changes in headgroup orientation, lipid fluidity) or in bulk (lipid demixing, membrane curvature). The resolution achieved through atomistic MD can be directly compared with other tools such as NMR and EPR to gain a full perspective of how these biological systems behave over different timescales. As my background is in computational physics, this thesis not only looks into broadening our understanding of various interactions with biological membranes, but also into the development of construction and analytical software to assist in my research and benefit others in the field. One aspect of biological membranes that could vastly benefit from MD simulations is that of antimicrobial peptides (AMPs). These peptides primarily target and destroy microbes by permeabilising the cell membrane through a variety of proposed mechanisms, where each mechanism relies on the AMP to adopt specific conformations upon contact with bacterial membranes. In this thesis, I present an investigation into the interactions between a synthetic AMP and an inhibitor peptide designed to regulate antimicrobial activity through the formation of a coiled coil structure, which restricts the AMP from adopting new conformations. Simulations captured the spontaneous formation of coiled coils between these peptides, and specific residues in their sequences were identified that promote unfolding. This knowledge may lead to better design of coiled coil forming peptides. Another aspect of biological membranes that can be explored with MD is the interactions between model bacterial membranes and amphipathic helices, such as the MinD membrane targeting sequence (MinD-MTS). This 11-residue helix is responsible for anchoring the MinD protein to the inner membrane of Bacillus subtilis and plays a crucial role in bacterial cell division. MinD is known to exhibit sensitivity to transmembrane potentials (TMVs), whereby its localisation and binding affinity to bacterial membranes are disrupted upon removal of the TMV. Simulations revealed rapid insertions of MinD-MTS peptides into the headgroup region of a model bacterial membrane. Analytical software was constructed to measure the membrane properties of the lipids surrounding inserted MinDMTS peptides, which revealed splayed lipid tails and suggests the MinD-MTS may be capable of inducing membrane curvature. Additional simulations were conducted to investigate the influence of a TMV on model bacterial membranes, where software was constructed to measure changes in membrane properties. An analysis of these simulations suggests that a TMV is capable of lowering the transition temperature of a model bacterial membrane by a few degrees, yielding increased fluidity in the lipids and increased perturbations on the membrane surface. Finally, another aspect of biological membranes that can be explored through MD is that of electroporation. This induction of transient water pores in cell membrane provides an exciting aspect for drug delivery applications into cells, whereby electric fields are applied to cells to increase the uptake of therapeutic drugs. Simulations of membranes with high voltage TMVs were conducted that sought to investigate the implications of electroporation across a variety of bilayer compositions at different temperatures. Software was constructed to measure changes in membrane and system properties, which revealed that pore formation occurred at the same threshold voltage for different bilayer compositions in the fluid phase (~1.9 V) and a higher voltage for DPPC bilayers in the gel phase (~2.4 V). The TMV was found to be highly dependent on the area per lipid (APL), implying that bilayers with bulkier lipids or those transitioning from gel to fluid will experience smaller TMVs and fewer pore formations. These simulations also revealed lipid flip-flopping through pores, where charged lipids tended to translocate in the direction of the electric field to produce an asymmetrically charged bilayer. Finally, simulations utilising charged peptides with membranes yielded electroporation effects, whereby the charged peptides generate an identical TMV to those produced by an ion imbalance of equal magnitude. This suggests that charged peptides, such as AMPs, may be capable of permeabilising cell membranes through electroporation mechanisms.
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Shrestha, Jaya P. "Synthesis, Structure-Activity Relationship Study, and Mode of Action Study of 1,4-Naphthoquinone Based Anticancer and Antimicrobial Agents." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/4925.
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Synthesizing bioactive small molecules by structural modification of 1,4-naphthoquinone was the primary goal of this research. Several bioactive compounds with anticancer, antifungal, and antibacterial activities were synthesized. All the synthetic protocols were optimized in such ways that do not require cumbersome purification.
First, a new protocol for the synthesis of NQM111 was developed. NQM111 is a highly potent anticancer agent developed in our laboratory, but the old protocol does not provide enough quantity for in vivo study. Therefore, a new safe and improved method was developed which provides enough quantity for in vivo study.
The second project involves the synthesis of 1,4-naphthoquinone conjugated with an aromatic group. These compounds are a highly potent anticancer agent with ~8-fold selectivity towards cancer cell lines than the non-cancer cell line. A mode of action study of this compound was identified, and it was observed that these compounds generate reactive oxygen species,which triggers apoptosis.
The final project involves the synthesis of 1,4-naphthoquinone based antifungal, and antibacterial compounds. These compounds are multi-cationic in nature with a hydrophobic tail. Six different analogs with varying hydrophobic tails were synthesized and tested for their antibacterial and antifungal activity. These compounds showed excellent activity against wide range of fungi including resistant strains.
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Chan, Mei-sheung, and 陳美嫦. "Study of structure-function relationships in cationic antimicrobial peptides derived from human and porcine lactoferricins." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B43572017.
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Chan, Mei-sheung. "Study of structure-function relationships in cationic antimicrobial peptides derived from human and porcine lactoferricins." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43572017.
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BARZAN, GIULIA. "Study of antimicrobial and antioxidant properties of new materials for development of active food packaging." Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2970684.
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This work is focused on the design, production and characterization of sustainable active food packaging materials with antimicrobial and antioxidant properties to ensure the safety and quality of foods and prolong their shelf-life.
Firstly, a microfluidic device combining dielectrophoresis (DEP) and Raman spectroscopy was developed for a fast and dynamic characterization of different bacterial strains, including food-related pathogens (i.e. E. coli and S. aureus), directly in planktonic suspension. Predictive models to identify bacterial cross-induced resistance to antibiotic within few hours were built using this method, overcoming the overnight incubation required by classical microbiological assays. Furthermore, Raman imaging was employed to detect the spatial distribution of different biomolecules at single cell level.
Then, the antibacterial properties of innovative silver and carbon-based nanosystems and their inclusion in prototype packaging materials were studied.
Differently sized silver nanoparticles, from 6 to 50 nm, were compared for their antibacterial efficacy in suspension and immobilized on glass. For the first time, the surface minimal bactericidal concentration (SMBC) of silver needed to kill 99.9999% of bacteria, was determined by ISO 22196, thereby facilitating the comparison between measurements and minimizing the amount of silver on the materials surface (0.023-0.034 μg/cm2) as well as their cost of production and toxicity.
Colloidal carbon nanoparticles (CNP), obtained by a green chemistry synthesis, were tested against Gram + and a Gram – bacteria, by classical microbiological assays and the DEP-Raman system, revealing a rapid interaction with the bacteria but not significant bactericidal effects. Thus, CNP were loaded with an antimicrobial peptide which increased their antibacterial activity, especially against S. aureus.
Finally, new antioxidant packaging modified with grape and olive industrial waste products and Moringa oleifera leaves obtained by different extractive procedures were produced and characterized. The antioxidant efficacy of many fractions of the plants extracts were analyzed by multiple standard assays and the results were correlated with their content of polyphenols obtaining higher values for anti-solvent and maceration extract fractions. The latter, resulting from a more sustainable extraction procedure, were included in cellulose-based active packaging systems. The antioxidant properties of such films were measured by indirect and direct analytical methods demonstrating good free radical scavenging properties for all the three kind of active agents and a higher radical reduction capacity of moringa. Additionally, the ability of the packaging coated with moringa (5% w/w) of delaying fresh ground beef oxidation was tested. This film was chosen as the best alternative to obtain the highest oxidative protection of meat on the basis of the in vitro results and ensuring a direct food-contact mechanism of action. This packaging revealed to prevent meat from lipid oxidation by at least 60% after 16 days compared to simple cellulose. Additionally, in situ analysis of the meat performed by vibrational spectroscopies evidenced also a protective action against protein and lipid degradation.
This work could be considered valuable in the field of food packaging because the use of sustainable and degradable materials to prolong the food shelf-life perfectly fits in the actual compelling need to reduce pollution and global waste production. This is in accordance with the 12th Sustainable Development Goal of the European Green Deal purpose to halve the global food waste production per capita by 2030, ensuring an efficient and sustainable use of natural resources. Hence, an innovative way to recover food industry waste is proposed and their antioxidant efficacy in active food packaging was demonstrated even on real food matrices with many different techniques strengthening the reliability of the results.
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Carlsson, Göran. "Kostmann syndrome : a clinical and pathophysiological study /." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-059-1/.
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Ferre, Malagon Rafael. "Design and synthesis of short antimicrobial peptides for plant protection. Study of their mode of action." Doctoral thesis, Universitat de Girona, 2010. http://hdl.handle.net/10803/8053.
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Aquesta tesi doctoral està basada en el desenvolupament de nous agents antimicrobians derivats del pèptid híbrid cecropina A-melitina WKLFKKILKVL-NH2 (Pep3) que siguin sostenibles i útils per al control de malalties de plantes. Es van dissenyar i sintetitzar més de 133 anàlegs de Pep3 mitjançant química combinatòria. Es van obtenir anàlegs de Pep3 amb una elevada activitat contra fitopatògens i que presentaven baixa toxicitat. Els millors anàlegs van presentar eficàcies comparables amb pesticides de referència en la prevenció d'infeccions causades per fitopatògens. Es va estudiar el mecanisme d'acció de KKLFKKILKYL-NH2 (BP100) investigant la seva interacció amb models de membrana mitjançant tècniques espectroscòpiques. Es va observar la capacitat de BP100 a induir la permeabilització, la neutralització, i l'agregació de vesícules lipídiques aniòniques a una determinada concentració llindar. Es va deduir una equació que relaciona la CMI d'un pèptid antimicrobià amb la constant de partició i la concentració llindar en la membrana.<br>This PhD thesis focused on the development of new sustainable antimicrobial agents derived from the cecropin A-melittin hybrid antimicrobial peptide WKLFKKILKVL-NH2 (Pep3) for use in plant protection. A set of 133 Pep3 analogues were designed and synthetized using a combinatorial chemistry approach. Analogues of Pep 3 with high antimicrobial activity and low toxicity were obtained. The best of them were highly effective preventing infections of phytopathogens being not significantly different to conventional pesticides. Insights into the mode of action of KKLFKKILKYL-NH2 (BP100) were carried out by investigating its interaction with different model membrane systems using spectroscopic methodologies. BP100-induced vesicle permeabilization, membrane electroneutrality, and vesicle aggregation at a defined threshold concentration. Moreover, it was deduced an equation that correlates the MIC of an AMP with the partition constant and the threshold concentration in the membrane.This equation provides an easily prediction of in vivo antimicrobial activities from simple biophysical parameters.
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Robinson, Gareth Michael. "Use of bacterial lux gene expression to study bacterial blood brain barrier penetration and antimicrobial effects." Thesis, University of the West of England, Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432309.
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Bioluminescence, the emission of light from living organisms, occurs throughout nature. In bacteria, bioluminescence is directly coupled to electron transport making it an excellent reporter of bacterial metabolic activity. The full lux operon from the terrestrial bioluminescent species, Photorhabdus IUl11inescens was transferred via a plasmid to the human pathogenic species, Staphylococcus alfrelfS and Neisseria meningitidis. The resulting transformants produced light constitutively and without the need for addition of exogenous substrate. Bioluminescent S. Ql~lreUS was challenged with the antimicrobial agent linezolid, and the inhibitory effect of the antibiotic on the organism at 6, 13 and 20 mg/L (Cmin, Cint and Cnax) along with its recovery following the withdrawal of linezolid was observable in real-time, by monitoring bacterial light output. Bacterial metabolism recovered more rapidly than bacterial replication (l.5 hours vs 3.5 hours at Cint) and the bacteriostatic nature of linezolid was confirmed since low light levels were detected throughout exposure to the drug. Bioluminescent Streptococcus pneul110niae (transformed prior to this study) was applied to a model blood-brain barrier (BBB) comprising a co-culture of cells grown on opposing sides of a polycarbonate membrane. By monitoring bioluminescence, it was possible to observe the anti-pneumococcal activity of gemifloxacin across the BBB in real-time, and non-invasively. Above the gemifloxacin MIC (0.16 mg/L), inhibition of metabolism was observed and a reduction in bacterial metabolism by sub-MIC gemifloxacin concentrations (0.03 and 0.13 mg/L) across the BBB was also recorded. Bioluminescent S. aureus and S. pneumoniae both demonstrated the potential of lux-expressing bacteria of clinical importance to be used as a novel, rapid and real time method of assessing antimicrobial efficacy when challenged directly, or in the presence of eukaryotic cell lines such as the model BBB. It was also possible to explore, using bioluminescent S. pneumoniae, factors which may damage BBB integrity and which are exploitable by bacteria. Bacterial penetration of the BBB is the key step in the pathogenesis of bacterial meningitis, but remains one of the most poorly understood aspects of the disease. Bioluminescent N. meningitidis was applied to the model BBB and, using low light camera equipment, it was possible to observe meningococcal penetration of the BBB in real time and in situ. By optimising growth conditions, BBB penetration time by N. meningitidis was reduced from 50 hours to 9 hours. This application has shown bioluminescence to be a valuable reporter of bacterial location and activity and has the potential to yield new information about the pathogenesis of meningococcal disease and meningitis in general
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Melo, Mary Anne Sampaio de. "Safe and effective parameters for using photodynamic antimicrobial chemotherapy in carious dentin: an in vitro study." Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=2851.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico<br>The elimination of bacteria inside the demineralized dentin layer might contribute for a more conservative approach in the restorative treatment of deep dentin caries lesions. This way, this in vitro study aimed to establish safe and effective parameters for using an LED (λ = 620-660 nm) associated to the photosensitizer toluidine blue O (TBO) in the disinfection of artificially produced dentin caries lesions. For this, slabs with 25 mm2 of flatted occlusal human dentin were immersed for 5 days in BHI broth inoculated with Streptococcus mutans for caries induction. After demineralization, the slabs were randomly allocated to 10 experimental groups (n=15), as follows Control5; Control10; Control15; TBO; LED5; LED10; LED15; PDT5; PDT10 and PDT15, which were treated with TBO (0.1 mg.ml-1 for 5 min) or 0.9% NaCl solution for 5, 10 or 15 min, and submitted or not to LED irradiation for 5, 10 or 15 min (47, 94, and 187 J/cm2). Dentin samples from caries lesions were collected before and after treatments and bacteria were then cultured for Streptococcus mutans counts. In addition, using a type K thermometer, the temperature inside the pulp and in periodontal area was monitored for the groups PDT5, PDT10 and PDT1510 in 10 teeth with deep occlusal cavities. Paired t test/Wilcoxon matched pairs test (=5%) were used to determine differences between microbial population before and after treatments, and ANOVA followed by Tukey test for comparing data of temperature and log reductions. Statistically significant differences in Streptococcus mutans viability were found for the groups: Control15; LED15; PDT5; PDT10 and PDT15. The temperature from intrapulpal and periodontal area were lower than 2oC, being higher inside the pulpal chamber for group PDT15 when compared to group PDT5. Thus, it the experimental conditions used in the study, photodynamic therapy may be a safe and effective treatment to be used for disinfecting carious dentin, however the influence of time of irradiation/exposition it the Streptococcus mutans viability should be better investigated.<br>A eliminaÃÃo de bactÃrias presentes na camada de dentina desmineralizada poderia contribuir para uma abordagem mais conservadora no tratamento restaurador de lesÃes de cÃrie dentinÃria profundas. Desta forma, este estudo in vitro objetivou estabelecer parÃmetros eficazes e seguros para a utilizaÃÃo de um LED (λ = 620-660 nm) associado ao fotossensibilizador azul de orto-toluidina (TBO) na desinfecÃÃo de lesÃes de cÃrie dentinÃria produzidas artificialmente. Para tal, blocos com 25 mm2 de dentina oclusal planificada foram imersos por 5 dias em BHI caldo inoculado com Streptococcus mutans para induÃÃo de cÃrie. Depois da desmineralizaÃÃo, os blocos foram aleatoriamente distribuÃdos em 10 grupos experimentais (n=15), a saber: Controle5; Controle10; Controle15; TBO; LED5; LED10; LED15; TFD5; TFD10 e TFD15, que foram tratados ou nÃo com TBO (0,1 mg.ml-1 por 5 minutos) ou soluÃÃo de NaCl a 0,9% por 5, 10 ou 15 minutos, e submetidos ou nÃo a irradiaÃÃo com LED por 5, 10 ou 15 minutos (47, 94, e 187 J/cm2). Amostras de dentina cariada foram coletadas antes e apÃs os tratamentos e as bactÃrias foram semeadas para contagem de Streptococcus mutans. Adicionalmente, com um termÃmetro tipo K, a temperatura intra-pulpar e da Ãrea periodontal nos grupos TFD5; TFD10 e TFD15 foi monitorada em 10 dentes com cavidades oclusais confeccionadas em dentina profunda. Teste t pareado e ANOVA seguida pelo teste Tukey (=5%) foram usados para verificaÃÃo da reduÃÃo microbiana promovida pelos tratamentos, bem como para verificaÃÃo da alteraÃÃo na temperatura durante a irradiaÃÃo. DiferenÃas significativas estatisticamente na viabilidade do Streptococcus mutans entre contagens foram observadas nos grupos: Controle15; LED15; TFD5; TFD 10 e TFD15. A temperatura intra-pulpar e no periodonto foi inferior a 2oC, sendo a no interior da cÃmara pulpar maior para o grupo TFD15 quando comparado ao grupo TFD5. Dessa forma, nas condiÃÃes experimentais atuais, a terapia fotodinÃmica pode ser um tratamento eficaz e seguro a ser usado na desinfecÃÃo de dentina cariada, contudo a influÃncia do tempo de irradiaÃÃo ou exposiÃÃo à soluÃÃo salina na viabilidade do Streptococcus mutans deve ser melhor investigada.
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Diyoka, Nkongolo Jean Blaise. "Synthesis, characterization, and study mode of coordination of N,N’- and N,O - (arene)ruthenium II complexes co-ligated by isoniazid: Preparation for antimicrobial studies." University of the Western Cape, 2018. http://hdl.handle.net/11394/6574.
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>Magister Scientiae - MSc<br>This thesis reports on the syntheses of complexes of (arene) ruthenium (II) isoniazid Schiff base
ligands for antimicrobial studies. Isoniazid Schiff base ligands; isonicotinyl acid (2-hydroxy-5-
methyl-benzilidene)-hydrazide (L1), isonicotinyl acid (2-hydroxy-5-methoxy-benzilidene)-
hydrazide (L2), isonicotinyl acid (-5-chloro-2-hydroxy-benzilidene)-hydrazide (L3), isonicotinyl
acid (-5-bromo-2-hydroxy-benzilidene)-hydrazide (L4), isonicotinyl acid (2-hydroxy-5-nitrobenzilidene)-
hydrazide (L5) were prepared by condensation reaction under reflux from
equimolar amounts of isioniazid, which is an amine, with five different aldehyde moieties.
Ruthenium (II) complexes of these isoniazid Schiff base ligands (C1 - C5) were prepared in an
ethanolic solution under reflux and inert atmosphere at 60°C using Schlenk techniques.
Fourier transform infrared spectroscopy (FTIR), ultraviolet – visible spectroscopy,
thermogravimetric analysis, nuclear magnetic resonance and elemental analysis were the
characterization techniques that confirmed the successful preparation of the ligands. All the
ligands spectra displayed the imine functional group peak which confirmed the successful
preparation.
The ligands L1 – L5 and the complexes C1 – C5 were subjected to similar characterization
techniques which further confirmed the successful syntheses and the coordination of metal and
ligand by displaying a shift in their respective imine peaks and transitions values.
All the synthesized compounds were subjected to a standard antimicrobial test using three
microorganisms, Staphylococcus aureus, Methicillin resistant Staphylococcus aureus and
Pseudomonas aeruginosa. Out the ten compounds tested, only ligand L5 gave the best results
against Staphylococcus aureus.
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Galo, Ítalo Dany Cavalcante. "Fototerapia antimicrobiana: otimização de protocolo experimental in vitro e estudo de resistência bacteriana." Universidade Federal de Goiás, 2018. http://repositorio.bc.ufg.br/tede/handle/tede/8805.
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Previous issue date: 2018-07-16<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES<br>Bacterial infections increase significantly the rate of morbidity and mortality in the
hospital setting, which is substantially aggravated by the presence of bacterial
resistance. For this reason, research that brings therapeutic alternatives that are
efficient, cheap and safe in the fight against different infectious agents are necessary.
One potential therapy is antimicrobial phototherapy, especially represented by blue
light, which shows promise but still requires study and adjustments as to the best way
of application. Thus, the present study aimed to verify the antibacterial action of blue
light using different experimental protocols in order to clarify contradictions reported
in the literature on the subject and to determine a reproducible protocol for the study of
bacterial resistance. In vitro cultures of S. aureus, E. coli, P. aeruginosa, K.
pneumoniae, S. epidermidis, E. faecalis and C. albicans were performed specifically
for each test of light irradiation by blue ( 470 nm) or red (660 nm) light LED emitters.
Different variations of light application were performed under two conditions: after
inoculation and before inoculation in agar. In addition, preliminary testing was
performed to verify the possible development of bacterial resistance to blue light. All
of the in vitro assays evidenced important bacterial growth inhibition, showing that the
possible inherent biases found in the literature can be eliminated with the adoption of
specific protocol measures and that, in fact, the blue light inhibits the growth of these
infectious agents. It has been demonstrated that, in all cases, the use high application
times (and hence doses) of blue light is required to have better inhibition. The
resistance test performed suggests higher sensitivity of S. aureus in relation to P.
aeruginosa and E. coli, showing evidence that E. coli tends to become more resistant to
successive applications of this photoemission. The present study evidences that the
blue light has antibacterial action in all the in vitro protocols tested, being indicated the
use of light application with the infectious agent in liquid medium rich in nutrients as a
way of optimizing subsequent tests of greater complexity. The test of resistance to the
blue light adopted evidences more tendency to resistance by the bacterium Escherichia
coli in relation to other species tested.<br>Infecções bacterianas aumentam significativamente a morbidade e mortalidade no
âmbito hospitalar, quadro que se agrava substancialmente na presença da resistência
bacteriana. Por esta razão, pesquisas que tragam alternativas terapêuticas que sejam
eficientes, baratas e seguras no combate a diferentes agentes infecciosos são
necessárias. Uma terapia em potencial é a fototerapia antimicrobiana, representada
especialmente pela luz azul, a qual se mostra promissora, mas, ainda demanda de
estudo e ajustes quanto a melhor maneira de aplicação. Assim, o presente estudo teve
como objetivo verificar a ação antibacteriana da luz azul utilizando diferentes
protocolos experimentais a fim de esclarecer contradições reportadas na literatura sobre
o tema e determinar um protocolo reprodutível para estudo de resistência bacteriana.
Foram realizadas culturas in vitro de S. aureus, E. coli, P. aeruginosa, K. pneumoniae,
S. epidermidis, E. faecalis e C. albicans de forma específica para cada teste de
irradiação luminosa obtida por meio de emissores LED de luz azul (470 nm) ou
vermelha (660 nm). Foram realizadas diferentes variações de aplicação da luz em duas
condições: após semeadura e anterior à semeadura em ágar. Além disso, foi feito teste
preliminar para verificação de possível desenvolvimento de resistência bacteriana à luz
azul. Todas as análises in vitro adotadas evidenciam importante inibição bacteriana,
mostrando que os possíveis viesses inerentes a trabalhos encontrados na literatura
podem ser eliminados com a adoção de medidas protocolares específicas e que, de fato,
a luz azul inibe o crescimento destes agentes infecciosos. Foi demonstrado que, em
todos os casos, é necessário o uso de elevados tempos de aplicação (e,
consequentemente, doses) de luz azul para se ter melhor inibição. O teste de resistência
realizado sugere maior sensibilidade da S. aureus em relação a P. aeruginosa e E. coli,
e mostra evidências de que a E. coli tende a se tornar mais resistente à aplicações
sucessivas desta fotoemissão. O presente estudo evidencia que a luz azul possui ação
antibacteriana em todos os protocolos in vitro testados, sendo indicado o uso de
aplicação da luz com o agente infeccioso em meio líquido rico em nutrientes como
forma de otimizar testes de maior complexidade subsequentes. O teste de resistência à
luz azul evidencia maior tendência à resistência por parte da bactéria Escherichia coli
em relação a outras espécies testadas.
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Meyers, B. A. (Bruce Anthony). "A study on the bacteria of dog bite wounds in dogs and their susceptibility to antimicrobials." Diss., University of Pretoria, 2008. http://hdl.handle.net/2263/26742.
Full textAbstract:
To investigate the bacterial composition of infected and non-infected dog bite wounds (DBW), a prospective study was performed on dogs with various grades of bite wounds presenting at the Onderstepoort Veterinary Academic Hospital, University of Pretoria, and a nearby animal shelter. Fifty dogs with bite wounds inflicted within the previous 72 hours were selected. This represented 104 wounds. Wounds were clinically graded according to severity. Swabs were collected from all wounds for bacterial culture and cytology. Infection was diagnosed if 2 of the following 3 criteria were met: macroscopic purulence, microscopic presence of phagocytosed bacteria, or pyrexia. Non-infected wounds were either classed as sterile (established by culture) or contaminated (culture positive but bacteria not phagocytosed on cytology). To determine the origin of the bacteria, swabs were collected from the skin near the wounds and gingiva of 15 bite victims. All swabs were cultured aerobically and anaerobically and all aerobic cultures were evaluated for antimicrobial susceptibility using the Kirby Bauer disk diffusion test. The victims were predominately male, uncastrated, small-breed dogs. Of the 104 wounds studied, 21 were judged to be infected and 83 non-infected. Infected wounds were significantly more likely to culture positive (Fisher's exact test: p = 0.02). Sixteen per cent of wounds did not culture bacteria, 67% grew aerobes only, 1% anaerobes only and 67% a mixture of aerobes and anaerobes. A total of 213 isolates were cultured representing a mean of 2 isolates per wound. Of the aerobe species cultured, 22%, 19% and 17% belonged to the genera of Pasteurella, Streptococcus and Staphylococcus respectively. The species of Pasteurella multocida (66%) and Staphylococcus intermedius (70%) were predominant. Pasteurella canis and pyogenic streptococci were common in infected wounds, whereas Bacillus spp., Actinomyces spp. and oral streptococci were usually found in contaminated wounds. Three anaerobic genera were cultured, namely, Prevotella, Clostridium and Peptostreptococcus, and were usually associated with wounds with dead space. This study also describes the first documented case of Capnocytophaga canimorsus in an infected dog bite wound. Notably clinical and cytological assessment was capable of establishing whether antimicrobials were required or not. Although no single antimicrobials was considered to be effective against all the bacteria, amoxycillin plus clavulanic acid, 1st and 3rd generation cephalosporins, ampicillin or amoxycillin and potentiated sulphonamides gave the best in vitro sensitivity results.<br>Dissertation (MMedVet(Surgery) Small Animal Surgery)--University of Pretoria, 2007.<br>Companion Animal Clinical Studies<br>unrestricted
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Aguilar-Luis, Miguel Angel, Apayco Leslie Casas, Valdez Carmen Tinco, et al. "Screening and Assessment of Antimicrobial Susceptibility of Periodontopathic Bacteria in Peruvian Patients with Periodontitis: A Pilot Study." Hindawi Limited, 2021. http://hdl.handle.net/10757/655883.
Full textAbstract:
Background. Severe periodontal disease is highly prevalent worldwide, affecting 20% of the population between the ages of 35 and 44 years. The etiological epidemiology in Peru is scarce, even though some studies describe a prevalence of 48.5% of periodontal disease in the general population. Periodontitis is one of the most prevalent oral diseases associated with site-specific changes in the oral microbiota and it has been associated with a socioeconomic state. This study aimed to determine the etiology and resistance profile of bacteria identified in a group of Peruvian patients with periodontal disease. Methods. Six subgingival plaque samples were collected from eight patients with severe periodontitis. Bacterial identification was carried out by an initial culture, PCR amplification, and subsequently DNA sequencing. We evaluated the antibiotic susceptibility by the disk diffusion method. Results. Variable diversity in oral microbiota was identified in each one of the eight patients. The bacterial genus most frequently found was Streptococcus spp. (15/48, 31.3%) followed by Rothia spp. (11/48, 22.9%), Actinomyces spp. (9/48, 18.8%), and Eikenella spp. (4/48, 8.3%). The most common species found was Rothia dentocariosa (8/48, 16.7%). The antimicrobial susceptibility assay varied according to the species tested; however, among all the isolates evaluated, Actinomyces naeslundii was resistant to penicillin and tetracycline; Eikenella corrodens was resistant to dicloxacillin; and Rothia dentocariosa was resistant to amoxicillin + clavulanic acid and metronidazole but also susceptible to trimethoprim-sulfamethoxazole. Conclusions. The most prevalent periodontal bacterium found in this study was Rothia dentocariosa. Specific antimicrobial therapy is required to improve the treatment outcomes of patients with periodontal disease and avoid antibiotic resistance.<br>Revisión por pares
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Alali, Walid Qasim. "Longitudinal study of antimicrobial resistance among Escherichia coli isolated from integrated multi-site cohorts of humans and swine." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2434.
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Yunoki, Tomoyuki. "Genetic identification and antimicrobial susceptibility of clinically isolated anaerobic bacteria: A prospective multicenter surveillance study in Japan." Kyoto University, 2018. http://hdl.handle.net/2433/233837.
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Collins, Tracy Lynn. "A Study of Surface Motility and Biofilm Formation in Pseudomonas aeruginosa: Quorum Sensing and Photodynamic Antimicrobial Chemotherapy." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1291235249.
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Luke, Nicholas L. "A comparison of the antimicrobial efficacy of silver diamine fluoride and silver nitrate: an in vitro study." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5294.
Full textAbstract:
A COMPARISON OF THE ANTIMICROBIAL EFFICACY OF SILVER DIAMINE FLUORIDE AND SILVER NITRATE: AN IN VITRO STUDY
By: Nicholas L Luke, D.D.S.
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Dentistry at Virginia Commonwealth University.
Virginia Commonwealth University, May 2018
Thesis Advisor: William O. Dahlke Jr., D.M.D.
Pediatric Dentistry, Department Chair
Purpose: To determine the antimicrobial efficacy of SDF and SN/NaF.
Methods: Three bacterial species were combined to create an in vitro biofilm. Treatment was completed with SN, SN/NaF, SDF, SDF½ or untreated (control).
Results: The untreated group demonstrated significantly higher growth than all other treatment groups across the study. On the BHI-plates (1-day), there were significant differences between all treatments except SDF and SDF½. On the BHI-plates (3-days), SN/NaF was not significantly different from SDF or SDF½. On the L-MRS-plates (1-day), both SN treatment groups yielded significantly higher growth than the SDF groups. On the L-MRS-plates (3-days), SN yielded significantly higher growth than SN/NaF, SDF, and SDF½.
Conclusion: SDF is more effective than SN/NaF, with the exception of BHI-plates (3-days) only and SN/NaF is more effective than SN on primarily S. mutans and L. acidophilus. There is evidence of a possible antimicrobial tolerance of oral bacteria to silver.
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AlNajjar, Reham M. "A comparison of the antimicrobial efficacy of silver diamine fluoride and silver nitrate: an ex vivo study." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5800.
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A comparison of the antimicrobial efficacy of silver diamine fluoride and silver nitrate on various cariogenic bacteria: an ex vivo study By: Reham AlNajjar, D.D.S.
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Dentistry at Virginia Commonwealth University. Virginia Commonwealth University, 2019
Thesis Advisor: William Dahlke, D.M.D., Associate Professor and Chair of Pediatric Dentistry, School of Dentistry
Purpose: The use of silver-based antimicrobials is an emerging method for the treatment of dental caries. In this study, the authors compare the efficacy of the two most prominent silver- based therapeutics, silver diamine fluoride (SDF) and silver nitrate (AgNO3), on cariogenic and non-cariogenic multispecies biofilms. Currently there is a lack of studies comparing the efficacy of SDF to AgNO3.
Methods: Plaque samples from anterior and posterior tooth sites from children presenting both with early childhood caries and caries-free children were collected, pooled, and utilized to create four ex vivo biofilm systems in artificial saliva. SDF and AgNO3 were administered to these biofilms and bacterial survival was quantified and compared to untreated controls.
Results: Each of the four pooled sample types was applied to plates coated in artificial saliva + 1% sucrose. Both SDF and AgNO3 were very effective against plaque derived biofilms when compared to untreated biofilms (P0.05) in the potency of each compound.
Conclusions: SDF and AgNO3 significantly inhibit ex vivo cariogenic and non-cariogenic biofilms at similar levels.
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Subedi, Yagya P. "Cost-Effective Synthesis, Bioactivity and Cellular Uptake Study of Aminoglycosides with Antimicrobial and Connexin Hemichannel Inhibitory Activity." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7699.
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Amphiphilic kanamycin is one of the promising class of compounds for the treatment of fungal infections in plants and animal. Factor that lead to the restricting of compounds for commercialization includes, the higher cost of production and poor stability of the compound. However, the new lead, identified from the synthesis and biological testing, can be synthesized on a large scale with a cost comparable to commercial antifungals. The newly reported lead is stable at the acidic and basic conditions. Additionally, this compound has an excellent activity towards Candida auris, a multidrug-resistant superbug.
Heart disease is the leading cause of death in the United States most of which are caused by cardiac ischemia and arrhythmias. Abnormal opening of Cx43 hemichannel can damage the heart muscles and lead to these conditions. A compound which can selectively inhibit the opening of Cx43 hemichannel may pave the way to reducing the mortality rate of heart disease. A selective inhibitor towards Cx43 hemichannel is explored from the synthesis and biological testing of kanamycin derivatives. The synthesis of the new inhibitor is scalable and cost-effective.
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Lai, Ming-Qin, and 賴明欽. "The Study of Chitosan Antimicrobial Fiber." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/76431525485192860368.
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碩士<br>大葉大學<br>食品工程學系碩士班<br>91<br>Chitosan/cellulose antibacterial fibers were prepared by blending chitosan particle, cellulose and N-metheylmorpholine N-oxide (NMMO) together for spinning. The dope’s viscosity decreased along with the chitosan concentration. The fibers’ mechanical properties and antibacterial activities against Staphylococcus aureus (CCRC10451, ATCC6538P) were measured. Although the addition of chitosan reduced the mechanical properties, the elongation properties were increased. The antibacterial activity increased along with the chitosan concentration and slightly decrease it for hot-water treatment test.
The themogravimetry analysis results show insignificant decomposition temperature different for all samples.
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Chen, Chun-Hwa, and 陳俊樺. "Structural study of antimicrobial peptide Maximin H5." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/69919300566154249020.
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碩士<br>國立成功大學<br>生物科技研究所碩博士班<br>94<br>Amphibian skin is a rich resource of antimicrobial peptides, serves as the first line of defense of creatures attacked by microbes. The antimicrobial peptide studied here is an antimicrobial peptide from skin secretion of toad, Bombina maxima. It is a novel maximin H peptide which is produced through posttranslational modification of a precursor protein, and was named Maximin H5.
By analyzing the composition of amino acids, it contains three acidic aspartates, but has no basic amino acids. Based on the previous study, it seemed to be sensitive only to Gram positive bacteria. So far, few acidic antimicrobial peptides were found and little was known about their three-dimensional structures and mechanisms of killing microbes. In order to understand the structure-function relationship of maximin H5, we used NMR spectroscopy and structure calculation techniques to determine its three-dimensional structure and elucidate the bactericidal mechanism from the characteristics of three-dimensional structure.
Estimated the secondary structures from the chemical shift index, we found maximin H5 seemed to have helical structure at C-terminal region, but there is no obvious helical structure existed based on the calculated structure. Moreover, the surface charge of maximin H5 distribution graph showed that there is no amphipathic structure existed. In addition, its overall negative charge made it hard to attach to bacterial membrane. In conclusion, we propose the bactericidal mechanism of maximin H5 may not directly interact with the membrane of bacteria.
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CHIOU, WEN-CHIN, and 邱文欽. "Antimicrobial Effect and the Study of Pharmacy." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/94520958264777003757.
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Lo, Chang-Hung, and 羅昌鴻. "Study on production of antimicrobial peptides from soymilk." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/33461082523241438254.
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碩士<br>國立中興大學<br>食品暨應用生物科技學系所<br>98<br>To explore the preparation of antimicrobial peptide activity from soy protein peptides, the orientase were applied for preparing the protein hydrolysates from soy milk. In the experiment, five pathogens, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Salmonella choleraesuis were focused in this study and it was found that the orientase protein hydrolysates has the feature of antimicrobial activity. The preparation condition was defined as E/S = 1/100 (w/v), 50℃, pH 7.0, 1 h.
Higher antimicrobial activity inhibitor was obtained from separating the protein hydrolysates through the molecular sieve. After separation, five major fractions was obtained as: ≦3kDa, 3-5kDa, 5-10kDa, 10-30kDa and 30-50kDa. The fraction with highest activity had the molecular weight of 3-5kDa; the inhibitory effects of MIC (minimal inhibitory concentration) for five pathogens were 90 μg/mL, 100 μg/mL, 80 μg/mL, 80 μg/mL, 80 μg/mL,repectively. As for IC50 (fifty percent inhibitory concentration), they were 362.7 μg/mL, 286.1 μg/mL, 225.8 μg/mL, 240.6 μg/mL, 229.8 μg/mL,repectively.
We then determined the changes on peptide activity after hydrolysis through the intestine and to apply the gastrointestinal enzymes to digestion test. The results showed that 3-5kDa fraction with pepsin hydrolysis (pH 3.0, 37℃) decreased the anti-microbial activity; and after hydrolyzed through trypsin and chymotrypsin (pH 8.0, 37℃), the anti-microbial activity remained unchanged, therefore, it can be speculated that 3-5kDa fractions by digestive tract, digestive enzyme function as anti-microbial activity caused decreased.
These results suggest that the application of soymilk protein hydrolysis enzyme preparation could develop anti-microbial peptides, which in the future can be further studied and isolated to develop the antimicrobial effects for other microorganism.
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Cruz, Ana Filipa Daniel da. "Study of antimicrobial peptides' activity against bacterial biofilms." Master's thesis, 2017. http://hdl.handle.net/10451/30408.
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Tese de mestrado em Bioquímica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2017<br>O tratamento de infeções bacterianas é geralmente realizado recorrendo a antibióticos. Desde a sua descoberta, estes fármacos têm sido amplamente utilizados pois permitem aliar elevada eficácia e baixo custo. Porém, a prescrição excessiva e inapropriada de antibióticos conduziu ao desenvolvimento de resistência por parte das bactérias. Consequentemente, nos últimos anos, a eficácia dos antibióticos decresceu significativamente pelo que este problema se tornou uma ameaça global. Atualmente, estima-se que a resistência bacteriana a antibióticos seja responsável por cerca de 50 000 mortes por ano, apenas na Europa e nos Estados Unidos, e 700 000 mortes por ano em todo o mundo. Em 2014, a Organização Mundial de Saúde (WHO), emitiu um comunicado em que sublinhava a gravidade desta situação já que ameaça tornar novamente fatais infeções que, atualmente, são consideradas de fácil tratamento, como é o caso das infeções alimentares. Neste comunicado, a WHO frisou a necessidade eminente de novos fármacos eficazes no tratamento de infeções bacterianas e apelou ao seu desenvolvimento, especialmente contra várias estirpes bacterianas cujas hipóteses de tratamento estão seriamente comprometidas, como é o caso de Pseudomonas aeruginosa, Staphylococcus aureus e Enterobacteriaceae.
Os antibióticos convencionais atuam sobre processos metabolicamente ativos das bactérias. Com efeito, a especificidade de atuação destes fármacos facilita o desenvolvimento de resistência por parte das bactérias. Assim, nos últimos anos, têm sido realizados esforços no sentido de encontrar moléculas com mecanismos de ação alternativos de modo a evitar ou, pelo menos, dificultar este fenómeno. Neste âmbito, os péptidos antimicrobianos (AMPs) têm sido propostos como uma alternativa promissora face aos antibióticos convencionais.
Os AMPs correspondem a um grupo de moléculas existente na maioria dos organismos, incluindo vertebrados, plantas e invertebrados, fazendo parte do sistema de defesa destes organismos há milhares de anos. Os AMPs caracterizam-se, em geral, por apresentarem sequências curtas (12-50 resíduos de aminoácidos), carga global positiva devido à predominância de resíduos de aminoácidos básicos, como lisinas e argininas, elevado conteúdo em resíduos hidrófobos, como triptofanos, e ainda por adotarem uma estrutura anfipática na presença de membranas. Estes péptidos são vistos como uma alternativa promissora relativamente aos antibióticos convencionais por diversos motivos: i) uma vez que fazem parte do sistema de defesa dos organismos há milhares de anos sem que tenham induzido o desenvolvimento de resistência, é pouco provável que as bactérias venham a adquirir resistência à sua ação; ii) apresentam um largo espetro de atividade, atuando sobre bactérias, fungos e vírus; e iii) a sua ação é exercida ao nível da membrana bacteriana, por disrupção da mesma, processo este que é independente do estado metabólico das células e desfavorável ao desenvolvimento de resistência por parte das bactérias.
Em trabalhos anteriores do laboratório de acolhimento (MCastanho lab do Instituto de Medicina Molecular) foi identificado um péptido derivado da proteína da cápside do vírus da Dengue com atividade antibacteriana – pepR. No entanto, a sequência deste péptido é relativamente longa (35 resíduos de aminoácidos), o que reduz o seu potencial terapêutico. Deste modo, este trabalho teve como principal objetivo o estudo de péptidos derivados do pepR de modo a diminuir o tamanho da sua sequência ao mesmo tempo que era mantida, ou mesmo otimizada, a sua atividade antibacteriana. Neste sentido foram estudados 12 péptidos derivados do pepR, cuja sequência sofreu truncagens sequenciais de 2 resíduos de aminoácidos a partir do seu terminal N (péptidos N1-pepR/N6-pepR) ou terminal C (péptidos C1-pepR/C6-pepR), num total de 12 resíduos de aminoácidos a partir de cada extremidade, respetivamente. Idealmente, esta abordagem permitirá identificar a região mínima da sequência do pepR que é responsável pela sua atividade antibacteriana. O trabalho iniciou-se com a determinação da concentração mínima inibitória (MIC) de cada derivado contra as estirpes de referência Escherichia coli ATCC 25922 (Gram-negativa) e Staphylococcus aureus ATCC 25923 (Gram-positiva). Os resultados obtidos revelaram que todos os péptidos possuíam elevada atividade antimicrobiana contra E. coli; no entanto, no caso de S. aureus, apenas os péptidos C1- a C4-pepR e N1-, N3- e N4-pepR possuíam elevada atividade antimicrobiana. Estes resultados demonstraram que, neste último caso, o aumento do número de resíduos de aminoácidos truncados traduziu-se numa perda de atividade antibacteriana, sendo esta perda mais pronunciada quando a truncagem era efetuada no terminal C do pepR.
De forma a identificar possíveis alterações conformacionais associadas às truncagens sequenciais efetuadas, determinou-se o nível de estrutura secundária adotado pelos vários péptidos derivados do pepR através da técnica de dicroísmo circular (CD), sob três condições experimentais: em solução aquosa e na presença de sistemas membranares que simulam, respetivamente, a membrana plasmática animal e a membrana bacteriana. Os espectros de CD obtidos nas duas primeiras condições revelaram que todos os derivados apresentavam uma conformação random coil. Porém, na presença de sistemas membranares aniónicos, que mimetizam a membrana bacteriana, os espectros de CD obtidos foram característicos da conformação em hélice α. Por outro lado, constatou-se ainda que os péptidos que anteriormente demonstraram maior perda de atividade antimicrobiana (C5- e C6-pepR), apresentavam também menor conteúdo em hélice α sob estas condições experimentais. No seu conjunto, estes resultados evidenciaram uma relação clara entre a estrutura secundária adotada pelos péptidos na presença de membranas carregadas negativamente e a sua atividade antibacteriana. Estes resultados sugeriram ainda a existência de uma região na zona central da sequência do pepR que é responsável pela sua atividade antimicrobiana.
De forma a auxiliar a identificação desta região putativa do pepR responsável pela sua atividade antimicrobiana recorreu-se ao programa HeliQuest, uma ferramenta bioinformática que prevê a propensão de determinada sequência peptídica em adotar uma conformação helicoidal anfipática, propriedade esta considerada crucial para a atividade antibacteriana dos AMPs. O screening da sequência do pepR realizado com esta ferramenta permitiu identificar uma região central da sequência, ligeiramente deslocada para o terminal C, que apresenta elevada anfipaticidade. Analisando esta região mais detalhadamente, constatou-se que a perda de atividade antibacteriana e de estrutura helicoidal por parte dos vários derivados estudados ocorria em paralelo quando resíduos de aminoácidos pertencentes a esta região eram truncados, confirmando assim a sua relevância na atividade antimicrobiana apresentada pelos vários péptidos.
Posteriormente, foi ainda testada a atividade dos derivados do pepR e do próprio pepR contra uma estirpe produtora de biofilmes, Staphylococcus aureus ATCC 6538. Determinou-se a MIC e a concentração mínima bactericida (MBC) de todos os péptidos, obtendo-se resultados que classificaram a sua atividade antibacteriana como forte e a sua ação como bactericida, à exceção dos péptidos C5- e C6-pepR. Estes resultados corroboraram mais uma vez as conclusões anteriores sobre a relação estrutura-função existente na família dos vários derivados do pepR estudada.
Após esta fase inicial do trabalho, os péptidos N6-pepR e C4-pepR foram selecionados para estudar o seu mecanismo de ação ao nível molecular, uma vez que correspondiam às sequências truncadas com menor tamanho possível que ainda apresentavam uma atividade antimicrobiana elevada. O mecanismo de ação destes dois péptidos contra bactérias S. aureus ATCC 6538 planctónicas foi primeiramente estudado através da realização de um ensaio de cinética de morte bacteriana. Ambos os péptidos apresentaram uma cinética de morte rápida, sendo possível observar após apenas 15 minutos de exposição ao péptido a uma concentração idêntica à sua MBC aproximadamente 70% de morte, o que sugere uma atuação ao nível da membrana plasmática das bactérias. Este ensaio foi complementado com estudos de permeabilização membranar (por citometria de fluxo utilizando a sonda SYTOX Green) e de viabilidade celular (utilizando um ensaio de contagem de colónias). Os resultados obtidos mostraram a existência de uma correlação inversa entre estes dois parâmetros, confirmando que a morte bacteriana observada após exposição aos péptidos resulta de uma ação por disrupção membranar.
Por fim, os péptidos N6- e C4-pepR foram ainda testados relativamente à sua capacidade de inibir a formação de biofilmes de S. aureus ATCC 6538. Esta avaliação foi efetuada através da realização de dois ensaios: ensaio de viabilidade celular (redução de resazurina) e de quantificação da biomassa formada (por ligação do violeta de cristal). Ambos os péptidos apresentaram capacidade de inibir a formação de biofilmes a concentrações iguais ou superiores a 6.25 μM. A partir desta concentração, observou-se uma redução praticamente total da viabilidade celular e, concomitantemente, a inexistência de matriz extracelular polimérica.
Concluindo, neste trabalho foi possível identificar dois péptidos (N6- e C4-pepR) com atividade antibacteriana e capacidade de inibir a formação de biofilmes. Ambos os péptidos possuem uma sequência menor comparativamente ao pepR (com 23 e 27 resíduos de aminoácidos, respetivamente), possibilitando a sua utilização como “péptidos modelo” para a síntese/otimização de novos fármacos. No futuro, pretende-se proceder à síntese da região putativa, identificada como sendo responsável pela atividade antibacteriana do pepR. Deste modo, será possível comprovar a hipótese colocada sob a relação estrutura-função dos derivados do pepR estudados e, eventualmente, encontrar um derivado do pepR com uma eficácia antibacteriana superior ao pepR e aos segmentos truncados aqui investigados.
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Lin, Hsiu-Chen, and 林秀真. "Inappropriate Antimicrobial Usage in Urinary Tract Infection and the Study of Molecular Epidemiology on Antimicrobial Resistance of Enterobactericeae." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/bs8s2n.
Full textAbstract:
博士<br>臺北醫學大學<br>公共衛生學系暨研究所<br>102<br>Antimicrobial resistance of the pathogenic bacteria is a major concern of public health worldwide now. In the other word, Methicillin resistant Staphylococcus aureus, extended spectrum beta-lactamase (ESBL) producing Enterobacteriaceae may lead to the treatment more difficult than before. The major mechanism of antimicrobial resistance in bacteria is the inappropriate antimicrobial usage including the overuse and underuse. Upper respiratory tract infection is the major infectious disease of ambulatory patients. However, urinary tract infection (UTI) is the second infectious disease of those patients and is the major reason needed the antimcrobial prescription. The commonest pathogens of the UTI are the E. coli, K. pneumoniae, and P. mirabilis. According to the surveillance study by National Health Research Institute, the antimicrobial resistances of the three pathogens are increasing rapidly. The major resistance of these pathogens is from the production of ESBL. Nevertheless, the CTX-M is the major genotype of ESBL in the world. Clinically, the empirical antimicrobial treatment of the ESBL-producing bacteria infection is carbapenems. However, the hydrolysis ability to third generation cephalosporins is different from various kinds of CTX-M genotypes. For example, the CTX-M-14 (belong to CTX-M-9 group) is more susceptible to ceftazidime than CTX-M-15 (belong to CTX-M-1 group). But the CTX-M-15 type is resistant to all of the third generation cephalosporins. In other words, the physicians may choose the ceftazidime while the patients are infected with CTX-M-9 group ESBL-producing pathogen. They can avoid prescribing the broadest spectrum antimicrobials, such as carbapenem, for the UTI patients initially.
However, the physicians could choose the appropriate antimicrobials for the ambulatory patients with UTI and recognize the risk factors in the special care ward. It can result in the reduction of inappropriate antimicrobial prescription and decrease the antimicrobial resistance of bacteria. In addition, the surveillance study could provide the genotype of ESBL resistance of Enterobacteriaceae, and provide various susceptibility patterns for Enterobacteriaceae. Then, physicians could prescribe the appropriate antimicrobials for Enterobacteriaceae infection.
The first purpose of the present study is to investigate the treatment outcome of ambulatory patients with acute cystitis with inappropriate antimicrobials. Second, we explore the risk factors of patients acquiring the UTI with ESBL-producing Enterobacteriaceae in the respiratory care wards. The third purpose is to determine the molecular epidemiology of ESBL genotypes in Taiwan. It could demonstrate various antimicrobial susceptibility of ESBL resistance as a reference for treatment in clinics.
The longitudinal observational study was conducted using clinical records sampled from the National Health Insurance Research Database in Taiwan. It included one million persons. The ambulatory patients with acute cystitis were enrolled. These patients were classified into "adherence group" and "non-adherence group" according to the guideline established by Infectious Diseases Society Taiwan. Then, the outcome of UTI was defined recurrence of UTI-associated infections within 28 days. Furthermore, 240 isolates of urine culture from two respiratory wards (RCW) at Northern Taiwan. The demographic, clinical, and microbiologic data were analyzed to obtain the risk factors for acquiring the UTI of ESBL-producing Enterobacteriaceae. In addition, 477 isolates of ESBL-producing E. coli, K. pneumoniae, and P. mirabilis were collected from 20 hospitals distributed in Taiwan. PCR was performed in order to clarify the molecular epidemiology of genotypes of ESBL resistance.
In conclusion, physicians who adhered to recommend guidelines for the treatment of bacterial infections, had better therapeutic outcomes in their patients with acute cystitis, regardless of whether they had multiple chronic comorbidities. Thus, intensive implementation by physicians in all health care disciplines of patients with lower UTIs is necessary to ensure a discreet antibiotic policy that will decrease recurrence rates, and thus improve patient care. On the other hand, geriatric patients with recent exposure to two or more antibiotics and two or more numbers of comorbidities were at risk for ESBL-producing organism infection. Our results suggest that infection control procedures in RCW should be concerned with reducing antimicrobial prescriptions and patient comorbidities. In our study, we found the most prevalent genotype of CTX-M of ESBL in Taiwan is CTX-M-9 group; the second is the CTX-M-1 group. The study is the first report about isolated CTX-M-25 group, but the genotypes of CTX-M-8 and CTX-M-2 groups existed in Europe and America are not found in Taiwan untill now.
In conclusion, carbapenem may not be the first choice to treat ESBL-producing bacteria infection in Taiwan. We could use ceftazidime which is still effective to treat the CTX-M-9 group ESBL-producing Enterobacteriaceae.
Reducing the bacterial resistance should be approached from various manipulations. Our study found that patients would have a good clinical outcome and low recurrence rate if physicians would adhere to guidelines and prescribe appropriate antimicrobials for acute cystitis. We also indicated previous antibiotics prescribed to a geriatric patient with multiple chronic diseases in RCW should be carefully evaluated the risk factors of ESBL-producing organisms. These risk factors are different from other intensive care units. Moreover, the distribution of genotypes of CTX-M of ESBL resistance in Taiwan is different from other countries; it suggests different antimicrobial susceptibility of ESBL should be considered in Taiwan. All of above effort were done in order to attain the reduction of inappropriate antimicrobial usage.
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Hsu, Chin-Ping, and 徐近平. "Study on Compositions and Antimicrobial Activity of Commercial Seasonings." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/85829976926699293480.
Full textAbstract:
碩士<br>中國文化大學<br>生活應用科學研究所碩士在職專班<br>91<br>Abstract
Seasoning has became the main components of the meal as due to variety of seasoning be investigated. In this study, we try to evaluate the hygiene, safety, and quality of 43 commercial seasonings from market.
The AOAC method and CNS used to analysis general composition, Beaume (B′e), Brix contained, ration of amino acid and fatty acid composition in the commercial seasonings. The result shown that the commercial seasonings which contained water content 2~6%, water activities 0.2~0.5, pH value 5.3~8.5, Beaume (B′e) 8~10%, and Brix 7~11% is common. The composition of crude protein, crude fat, crude ash, and NaCl were changed by different product appearance. Glu is the highest content of amino acid in the seasoning, and then is NH3 and Gly. The result indicated that seasoning has different fatty acid composition based on the different seasoning appearance. For example, the curd shape has highest composition of saturate fatty acid then particle shape and powder shape, and curd shape has higher composition of saturate fatty acid then the composition of unsaturated fatty acid. The kelp and shiitake mushroom flavor seasoning have higher composition of saturate fatty acid then the composition of unsaturated fatty acid too. Seafood flavor seasoning contained EPA and DHA on them. The seasonings haven’t found any microbial inhibition effect from the result.
Key word：seasoning、general composition、amino acid、fatty acid
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Li, Szu Hsuan, and 李偲亘. "The Study of Production of Antimicrobial Substances from Microorganisms." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/22x4v6.
Full textAbstract:
碩士<br>國立金門大學<br>食品科學系<br>103<br>This research selected soil samples were screened to find excellent antimicrobial substances. By antimicrobial test to screen out the suppression effect of better strains. From the experimental results it could be determined that the soil samples screened 6 strains of inhibit indicator bacteria. Among the group "NO.4" and "1-4" had better results than other four types of bacteria, therefore this experiment carried on with only the two "NO.4" and "1-4" for further study. The culture conditions for most physical and chemical properties. The results showed that "NO.4" bacteria: showed the inhibition of Escherichia coli: where 1% carbon where the best source was maltose, 4% nitrogen in the form of urea, at a temperature of 25℃, and a pH value of 7, a mixing rpm speed of 180rpm, with a volume of 50mL, the inoculation amount was 1%, and the given culture time was 24 hours. The inhibition of Staphylococcus aureus: 3% carbon where the best source was maltose, 4% nitrogen with the source being isolated soy protein, the temperature was 25℃, with a pH value of 7, a mixing rpm speed was 180rpm, with a volume of 50mL, the inoculation amount was 1%, and the given culture time was 48 hours.The "1-4" bacteria: inhibition of E. coli: 1% carbon where the best source was corn starch, 5% nitrogen in the form of urea, and a temperature of 25℃, a pH value of 9, a mixing rpm speed was 180rpm, with a volume of 50mL, the inoculation amount was 1%, and the given culture time was 48 hours. The inhibition of S. aureus: 1% carbon where the best III source was corn starch, 3% nitrogen with the source being isolated soy protein, the temperature was 25℃, with a pH value of 9, a mixing rpm speed was 180rpm, with a volume of 50mL, the inoculation amount was 1%, and the given culture time was 72 hours. The fermented liquid of the bacteria strains "NO.4" and "1-4"of MIC and MBC tests were diluted by a factor of 40. The fermented liquid of the bacteria strains "NO.4" and "1-4" have thermal stability and pH stability. Metal ion test: The fermented liquid of "NO.4" adding K+、Zn2+ and The fermented liquid of "1-4" adding K+、Cr3+ both have increasing suppression
effect. According to the experimental results, the fermented liquid of the bacteria strains "NO.4" and "1-4" can have different degrees of antibacterial effect on E. coli and S. aureus, respectively. This antibacterial effect is worth exploring in further research.