Дисертації з теми "Virulent factors"
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Keller, Ninette. "Hypoglycaemia in virulent canine babesiosis prevalence and risk factors /." Diss., University of Pretoria, 2004. http://upetd.up.ac.za/thesis/available/etd-03082005-092252/.
Повний текст джерелаKitahara, Nao. "Study on screening of novel pathogenic factors of Candida albicans by proteome analysis and its putative virulent mechanism." Kyoto University, 2016. http://hdl.handle.net/2433/215600.
Повний текст джерела0048
新制・課程博士
博士(農学)
甲第19774号
農博第2170号
新制||農||1040(附属図書館)
学位論文||H28||N4990(農学部図書室)
32810
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 植田 充美, 教授 栗原 達夫, 教授 矢﨑 一史
学位規則第4条第1項該当
Yang, Guowei. "Photorhabdus virulence factors." Thesis, University of Bath, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425889.
Повний текст джерелаGuttmann, Daniel Mark. "Bacillus thuringiensis virulence factors." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621944.
Повний текст джерелаWright, K. "Genomics and virulence factors of Fusobacterium necrophorum." Thesis, University of Westminster, 2016. https://westminsterresearch.westminster.ac.uk/item/9ywy3/genomics-and-virulence-factors-of-fusobacterium-necrophorum.
Повний текст джерелаMonteil, Vanessa. "Analyses phénotypiques et génotypiques de différentes souches de dengue : applications en épidémiologie et recherche de facteurs de virulence." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM5038.
Повний текст джерелаFrom 50 to 100 million cases of dengue illness occurred every year in the world. Today, dengue virus is a public health problem with its emergence in Europe, particularly in France. DENV infection can be asymptomatic or be responsible for three distinct pathologies: one with flu-like symptoms (DF), another with moderate hemorrhage (DHF) and the last one with severe bleeding leading to shock syndrome (DSS). Host factors have an important role in the development of severe forms but implicated viral virulence factors stay not well described. The aim of this research work was to better understand these viral factors through study of dengue serotype 3 genotype III dynamics of circulation in Africa and through the characterization of three dengue serotype 1 strains in Cambodia. This work highlighted the circulation of variants during epidemics, allowing us to suppose that the presence of variants permits a better dissemination, as well as specific phenotypic and genotypic characteristics in vitro of strains associated with hemorrhagic forms or forms with shock syndrome in humans. These works were completed by the development of an original system of detection of dengue virus and other viruses of genus Flavivirus. This research work allowed identifying potential virulence factor specific to virus, opening the way for research on the role of certain viral proteins in pathogenicity
Ranc, Anne-Gaëlle. "Phenol Soluble Modulins et lipopolysaccharide de Legionella pneumophila : rôle dans la réponse immunitaire innée." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1010/document.
Повний текст джерелаLegionella pneumophila (Lp) is a ubiquitous intracellular bacterium found widely in the environment and is the cause of an opportunistic infection named legionellosis. The majority of the strains involved belong to serogroup 1 (Lp1) and to a specific subgroup named mAb3/1+, linked to a specific epitope expressed at the cell membrane. However the distribution difference between the strains found in the environment and the ones involved in pathology is not fully understood. We here studied two virulence factors of Lp. We first demonstrated the existence of Phenols Soluble Modulines (PSMs), smalls peptides that only have been described for Staphylococcus and found that the peptides that were predicted for Lp by in silico analysis were able to activate the innate immune response by NF-?B pathway and were able to have a cytotoxic activity. We also studied the lipopolysaccharide (LPS) of Lp. To found out if the predominance of some strains was linked to a diagnosis biais, we first evaluated the sensitivity of 3 urinary antigens tests against extracted LPS of strains belonging to all the sous-groups of Lp1 and serogroups of Lp. We then demonstrated that those tests are able to detect all LPS of Lp1, independently of mAb3/1 character. The sensitivities of the 3 tests were very variable for the other serogroups of Lp, but were too low to be able to detect those LPS in practice. We then used these extracted LPS to evaluate the innate immune response for different strains of Lp1. We demonstrated that mAb3/1- strains needed lower dose of LPS to activate the innate immune response than mAb3/1+ strains, which could be linked to a better clearance of the bacteria from the host, which doesn’t develop an infection. This work has studied two potentially virulent factors of Lp, which could partially explain the predominance of some strains of Lp in human pathology
Seixas, Rui Emanuel Antunes de. "Virulence of Salmonella typhimurium 1,4,[5],12:i:- : the new emergent strain." Doctoral thesis, Universidade de Lisboa, Faculdade de Medicina Veterinária, 2017. http://hdl.handle.net/10400.5/13925.
Повний текст джерелаSalmonella serovar 1,4,[5],12:i:- is presently considered one of the major serovars responsible for human salmonellosis worldwide. A multidisciplinary approach, including the fields of epidemiology, spatial statistics, clinical and applied microbiology was used to perform an extensive characterization of Salmonella 1,4,[5],12:i:- isolates obtained by the National Health Institute Dr. Ricardo Jorge, which was lacking due to the recent emergence. It was observed that cases are reported in most districts, being more frequent in the Portuguese coastland. Spatial statistical analysis showed a significant geographic clustering, pointing out for the importance of evaluating these areas to identify risk factors, in order to establish adequate prevention programs. The most relevant antimicrobial profile in this serovar is the tetra-resistance pattern (R-type ASSuT), displaying resistance to ampicillin, streptomycin, sulphonamides and tetracyclines. A high occurrence of R-type ASSuT isolates was observed in the isolates under study, with the majority harboring the resistance genes frequently associated with the European clone, namely blaTEM, sul2, straA-straB, tetB. Additionally, resistance to quinolones and 3rd generation cephalosporin was also detected. In Portugal, the rapid spread of Salmonella 1,4,[5],12:i:- R-type ASSuT might be related with the diversity of pulsotypes and also the presence of a core of virulence factors, including biofilm production. Biofilm-forming ability varied between sample locations and collection year, and can be one of the virulence features related with the rise of this serovar. Furthermore, biofilm formation was evaluated in vitro using a simulated human intestinal environment. In such conditions was observed an impairment of biofilm production, revealing that conditions mimicking the human intestinal tract can influence the biofilm-forming ability of the isolates under study. This research highlight the critical importance of close surveillance of Salmonella 1,4,[5],12:i:- in Portugal, including R-type ASSuT isolates. Information gathered may unravel Salmonella 1,4,[5],12:i:- features, prevent the dissemination to other regions and also benefit the medical community in order to rationalize salmonellosis antimicrobial therapeutics.
RESUMO - Virulência de Salmonella Typhimurium 1,4,[5],12:i:-, a nova estirpe pandémica* - Salmonella é uma bactéria Gram-negativa pertencente à família Enterobacteriaceae, sendo uma das principais responsáveis pela morbilidade e mortalidade associadas a toxinfecções alimentares. Pode manifestar-se num espectro de sintomatologia variado, incluindo a gastroenterite, a bacteriémia e a infecção focal. Este género incluí mais de 2600 serovares descritos, distribuídos por apenas duas espécies: Salmonella enterica que inclui todos os serovares patogénicos para os humanos e Salmonella bongori. Actualmente, um dos principais serovares responsáveis pela salmonelose humana em todo o mundo é o 1,4,[5],12:i:-. Este serovar é uma variante monofásica de Salmonella Typhimurium, muito semelhante a nível molecular, sendo caracterizado pela ausência da expressão do gene fljB. Devido à sua recente emergência, estudos que avaliem este serovar são escassos, particularmente em Portugal, o que definiu o âmbito desta investigação, que teve como objectivo a caracterização epidemiológica e microbiológica, tanto do ponto de vista fenotípico e genotípico, de isolados de Salmonella 1,4,[5],12:i:- obtidos em Portugal a partir de diferentes origens, incluindo amostras humanas, animais e ambientais. Numa primeira fase foi realizada uma caracterização demográfica, epidemiológica e espacial de todos os casos de Salmonelose 1,4,[5],12:i:- humana notificados em Portugal pelo Instituto Nacional de Saúde Dr. Ricardo Jorge (INSA), durante um período de 10 anos, desde 2001 a 2011. Foram recolhidos dados sobre a origem, ano e mês de amostragem, género, idade, distrito e município de residência dos pacientes. Foi realizada a análise estatística descritiva, bem como, a análise estatística espacial através do software SaTScan™, combinada com análise através de software de georeferenciação, o QGIS™, de forma a caracterizar a epidemiologia e identificar agrupamentos espaciais de risco superior de infecção por Salmonella 1,4,[5],12:i:- em Portugal. Globalmente, observou-se que em Portugal, a maioria dos distritos tem casos notificados de infecção por Salmonella 1,4,[5],12:i:-. Verificou-se também um aumento da incidência durante o intervalo de 2004 a 2011, com um maior número de casos na região litoral do país, incluindo distritos como Porto, Lisboa e Aveiro, o que pode ser explicado pela maior densidade populacional nestas áreas. A maioria das infecções ocorreu durante Maio e Outubro, e o menor número em Fevereiro, afectando principalmente indivíduos jovens.[...]*O autor escreve segundo o antigo Acordo Ortográfico
This work was supported by National Health Institute Doutor Ricardo Jorge (INSA) and funded by Centre for Interdisciplinary Research in Animal Health (CIISA)
N/A
Scott, David Albert. "Virulence factors of oral anaerobic spirochetes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0001/NQ30378.pdf.
Повний текст джерелаScott, David 1964 Jan 11. "Virulence factors of oral anaerobic spirochetes." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34446.
Повний текст джерелаAs free iron is severely limited in humans the means by which OAS may obtain sufficient iron to prosper in the sub-gingiva was examined. The resultant model suggests T. denticola obtains iron through the $ beta$-hemolysis of erythrocytes and the binding of liberated hemin by a 47-kDa outer membrane sheath (OMS) protein. The kinetics of the ligand-receptor interaction are presented and the receptor has been purified to apparent homogeneity from T. denticola. $ sp3$H-labeled hemin is not transported into the cell. Evidence is presented to show that T. denticola produces an iron reductase, which may facilitate the transport of ferrous iron across biological membranes. It is also shown that T. denticola (Td), T. vincentii (Tv) and T. socranskii (Ts) do not produce siderophores. In growth assays, under conditions of iron-limitation, T. denticola may use inorganic iron, a source unlikely to be available in vivo.
Hyaluronidase (Hase) activity is elevated in the gingival crevice during episodes of disease. Hase, when injected into the periodontal cavity under experimental conditions has been shown to result in connective tissue degradation. It is also known that T. pallidum, the agent of syphilis, produces a Hase that is critical to pathogenesis. Evidence is presented herein to show that Td, Tv and Ts all produce a hyauronoglucosaminidase (HGase). The identity and specificity of the Td HGase is confirmed through the use of enzyme inhibitors and activators, by electron microscope observations of the enzyme using the Hase inhibitor gold sodium thiomalate and anti-Apis mellifera venom antibodies and examination of the purity of the HA substrate using other polysaccharide degrading enzymes. As the HGase of these OAS would not migrate through a substrate-SDS PAGE system, we have employed hyaluronate (HA)- and chondroitin sulfate (CS)-absorbed nitrocellulose membranes to visualize HGase activity. The 59 kDa HGase of Td has been purified to apparent homogeneity through the conjugation of HA and CS to Affigel 701 beads.
The last subject to be addressed by this thesis pertains to the ultrastructure of oral spirochetes. Using the copper-containing dye, Alcian blue, we have shown that T. denticola produces an exopolysaccharide layer, in an electron microscopy investigation. The development of a stain for dark-field microscopy has simplified the observation of this layer. The exopolysaccharide layer may have relevance to the evasion of phagocytosis, to protection against colicins, immunoglobulins and bacteriophages, to adherence and perhaps to the immunogenicity of OAS inhabiting the sub-gingiva.
Cahill, Lori A. (Lori Anne). "Virulence factors in non-gastric Helicobacters." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50433.
Повний текст джерелаZhang, Xing. "Exploring fungal virulence using C. elegans." Thesis, Aix-Marseille, 2020. http://theses.univ-amu.fr.lama.univ-amu.fr/200924_ZHANG_406xehco6dvggp718z420kj_TH.pdf.
Повний текст джерелаAmong the candidates were several heat-labile enterotoxins, a protein family that is expanded in the genome of D. coniospora compared to other pathogenic fungi. We focused on 3 (DcEntA-C). Expression of DcEntA and DcEntB, but not DcEntC made worms sick and more susceptible to infection. Normally, D. coniospora infection provokes the induction of expression of antimicrobial peptide genes of the nlp and cnc families. Interestingly, expression of the single enterotoxin DcEntA blocked the transcription of both nlp and cnc genes. DcEntA acted by inhibiting the nuclear translocation of the STAT transcriptional factor STA-2, required for defence gene expression. We demonstrated that this effect was specific as DcEntA induced high expression of a STA-2-independent infection-inducible gene. In contrast, worms expressing the enterotoxin DcEntB exhibited a STA-2 dependent elevation of nlp-29 expression. DcEntB was localized to the nucleolus and affected nucleolus size and morphology. The molecular basis of these differences and the relative importance of these factors during infection was explored in detail. Our result revealed the complexity of fungal virulence strategies. Overall, by dissecting the mode of action of different virulence factors, this study allowed us to understand better fungal pathogenesis and the evolutionary arms race between host and pathogen
Angely, Christelle. "Propriétés mécaniques et fonctionnelles des cellules épithéliales respiratoires exposées à une toxine bactérienne : l’adénylate cyclase." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC0058/document.
Повний текст джерелаThe increase in respiratory infections involving virulent factors of bacterial origin has become a major public health issue. A better knowledge of the cell respiratory response in the course of the initial cell invasion by bacterial toxins is important from the pathophysiological and therapeutical point of views.The purpose of this work is to decipher the cellular and molecular mechanisms involved in the exposition of respiratory epithelial cells to the adenylate cyclase toxin (CyaA) produced by Bordetella pertussis which is the whooping cough agent. We have chosen this toxin for its multiple capacities of penetrating a wide range of eukaryotic cells. Indeed, this toxin enables direct translocation of its catalytic domain across the plasma membrane of target cells using the endogen calmoduline to increase the cAMP rate at supraphysiological levels. However, the effects of these changes on mechano-chemical signaling (mechanotransduction) pathways remain largely unknown while it affects cellular functions and cell integrity. So, we perform an evaluation of cellular functions as well as mechanical and adhesion properties of respiratory epithelial cells exposed to CyaA toxin in order to detect some critical modifications in the mechanotransduction processes.In a preliminary study aiming at defining physiopathological concentrations of CyaA toxin used in our experiments, we determined the cell viability degree for 3 concentrations of CyaA toxin (0.5; 5 and 10 nM). We found that the smallest concentration (0.5 nM) did not affect cell viability whereas inducing supraphysiological cAMP levels in less than one hour.Then, we assessed the effects of CyaA toxin on cell migration and repair phenomenon, on ciliary beating and on cell permeability of epithelial cells representative of the different levels of the respiratory tract. The toxin induces a decrease in cell migration and repair, an increase in cell permeability suggesting a weakening of lateral cell-cell junctions.Immunostaining was performed on intracellular and interfacial structures of alveolar epithelial cells exposed to the 3 concentrations of CyaA toxin. Results show that CyaA toxin is able to induce cytoskeleton remodeling and a decrease in the number of focal adhesions. Finally, a refined analysis of mechanical properties and adhesion parameters was performed on the same cells by 2 techniques of micro/nanomanipulation modified to permit at the same time, an evaluation of cell adhesion and cell rigidity (Atomic Force Microscopy with indentation and force spectroscopy to characterize the number of bond during adhesion reinforcement and multiscale Magnetic Twisting Cytometry). To evaluate the role of cAMP on cellular and molecular changes, we tested the enzymatically inactive form of CyaA toxin called CyaAE5 which could not permit to increase the intracellular cAMP rate.The AFM experiments have revealed that the main effect of CyaA toxin is to decrease the number of associated integrin-ligand bounds (meaning an alteration of clustering) while, at the smallest concentration of CyaA toxin, we observe an increase in cell rigidity with an individual bound reinforcement, a result consistent with MTC results. Nevertheless, CyaE5 does not exhibit such cellular effects. On the whole, these results suggest that CyaA toxin affects the mechanotransduction pathways of cells exposed to the toxin, a result which is in agreement with the expected effects of cAMP increase (notably cytoskeleton remodeling, lateral junction alteration and inhibition of Rac1 expression) what brings a new vision of the cytotoxicity induced by the adenylate cyclase toxin
Goundry, Amy Louise. "Leishmania virulence factors : inhibitors of serine peptidases." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6002/.
Повний текст джерелаRudkin, Justine K. "Investigating the virulence factors of Staphylococcus aureus." Thesis, University of Bath, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601682.
Повний текст джерелаHaghkhah, Masoud. "Study of virulence factors of Staphylococcus aureus." Thesis, University of Glasgow, 2003. http://theses.gla.ac.uk/952/.
Повний текст джерелаAmbrose, Helen. "The epidemiology and virulence factors of pneumocystis." Thesis, University of Oxford, 2003. http://ora.ox.ac.uk/objects/uuid:4357cc1c-07ea-4cc4-82eb-25ae5feeef89.
Повний текст джерелаFyfe, L. "Studies on Aeromonas salmonicida extracellular virulence factors." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376521.
Повний текст джерелаFindlay, Gordon. "Biogenesis of virulence factors in Vibrio cholerae." Thesis, University of Kent, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294636.
Повний текст джерелаDodson, Amanda. "Host factors affecting the virulence of Campylobacter." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557965.
Повний текст джерелаPort, Gary C. "Exploring the Listeria monocytogenes secretome : identification and functional characterization of novel virulence factors and secretion systems /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/4981.
Повний текст джерелаSouibgui, Eytham. "Rôle de la clathrine dans le processus infectieux du champignon phytopathogène Botrytis cinerea." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1076.
Повний текст джерелаFungi are the most important plant pathogens on agricultural and horticultural crops. Study of fungal pathogens remains essential to understand pathogenic process and control plant diseases. These organisms secrete high amount of degrading enzymes involved in plant decomposition and they feed by absorption of degraded nutriments. Secretory proteins were described to be transported form Endoplasmic Reticulum and Golgi apparatus to extracellular space through intracellular vesicles. In filamentous fungi, intracellular vesicles were observed using electron microscopy but their biogenesis process is still unknown. Therefore, elucidation of the process and the identification of proteins involved in secretory vesicles biogenesis remains a challenge to understand virulence factors delivery. A nonpathogenic mutant altered in the expression of the gene coding for clathrin heavy chain was selected in a random mutant library generated in the necrotrophic pathogen Botrytis cinerea,. This gene is essential in many organisms, thus a clathrin dominant negative mutant was generated and confirming the nonpathogenic phenotype observed on several host plant. In eukaryotic cells, clathrin heavy chain is mainly described to be involved in endocytosis, but it is also essential for high density secretory vesicles formation in yeast. Characterization of the mutants using a proteomic approach revealed a secretion defect of 82 proteins including known virulence factors, as Plant Cell Wall Degrading Enzymes and elicitors. Furthermore, the clathrin mutant revealed a strong reduction of intracellular vesicles production. Clathrin was also localized in living cells using fluorescent GFP-tag protein. Endocytosis was also studied and surprisingly, any observable defect was observed for clathrin mutants. This study demonstrated for the first time the essential role of clathrin in the infectious process of a fungal pathogen and its role in virulence factors secretion
Bertrand, Quentin. "Caractérisation de facteurs de virulence impliquant les systèmes de sécrétion bactériens." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAV058.
Повний текст джерелаPseudomonas aeruginosa is the causative agent of nosocomial infections. Those infections are a real threat to public health, considering that P. aeruginosa is a member of the ESKAPE pathogens family. Those pathogens developed numerous antibiotic resistance mechanisms that allow them to escape the lethality of common treatments. More than just resistant, P. aeruginosa is able to make use of several virulence factors, and among them, the type V secretion system, which is the main subject of my PhD.A new virulent P. aeruginosa strain was discovered in Grenoble University Hospital several years ago. This strain lacked the virulence factors of common studied cytotoxic strains but, still displayed high toxicity. This was related to the expression of two proteins, ExlB and ExlA, that are part of the T5SSb and display a complete new mechanism of action (no protein homologs are found). The ExlA toxin is able to form pores in the eukaryotic cell membrane leading to their death. The aim of my PhD was to understand on a molecular level the mechanism of ExlA toxicity.To decipher the activity of this toxin, we divided it in two domains, studied separately. Using NMR, SEC-MALLS, liposome floating assay, SAXS and AFM techniques, we were able to prove that the C-terminal domain of ExlA was a « molten globule » in solution and was able to form holes in reconstituted lipid bilayers. This domain seems to be the key to lipid interaction by the whole protein. Additional in vivo studies of the N-terminal domain and on full-length ExlA allowed us to propose a putative model of the mechanism of this novel toxin
Portman, Jonathan Lewis. "Virulence Factor Regulation in Listeria monocytogenes." Thesis, University of California, Berkeley, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10620349.
Повний текст джерелаListeria monocytogenes is a Gram-positive intracellular pathogen that is readily amenable to genetic manipulation and for which there are excellent in vitro and in vivo virulence models. These attributes have allowed a thorough examination of the molecular underpinnings of L. monocytogenes pathogenesis, however, there are still a number of major unresolved questions that remain to be answered. For example, it has been known for many years that L. monocytogenes rapidly changes its transcriptional profile upon access to the host cytosol, however the host cues and bacterial components that are involved in driving this change have remained continually unanswered. One large piece of evidence came when the long-sought co-factor for the primary virulence regulator, PrfA, was discovered to be the antioxidant tripeptide, glutathione. Glutathione was demonstrated to play a crucial role in the activation of PrfA in vivo— a finding that has since led to two important discoveries that are described herein. First, the activation of PrfA in vitro requires both exogenous glutathione and a metabolic licensing step that can be recapitulated by a chemically defined synthetic media. Second, glutathione also functions as a post-translational regulator of the pore-forming virulence factor, Listeriolysin O (LLO), by reversibly binding via an S-glutathionylation reaction and preventing membrane association of the LLO monomers. These discoveries elucidate numerous regulatory roles for glutathione during infection and describe how L. monocytogenes is able to sense and respond to critical host compartments to mount a successful infection.
Upon entry to the host cell cytosol, the facultative intracellular pathogen Listeria monocytogenes coordinates the expression of numerous essential virulence factors by allosteric binding of glutathione (GSH) to the Crp-Fnr family transcriptional regulator, PrfA. Here we report that robust virulence gene expression can be recapitulated by growing bacteria in a synthetic medium (iLSM) containing GSH or other chemical reducing agents. Bacteria grown under these conditions were 45-fold more virulent in an acute murine infection model and conferred greater immunity to a subsequent lethal challenge compared to bacteria grown in conventional media. During cultivation in vitro , PrfA activation was completely dependent on intracellular levels of GSH, as a glutathione synthase mutant (ΔgshF) was activated by exogenous GSH but not reducing agents. PrfA activation was repressed in iLSM supplemented with oligopeptides, but suppression was relieved by stimulation of the stringent response. These data suggest that cytosolic L. monocytogenes interpret a combination of metabolic and redox cues as a signal to initiate robust virulence gene expression in vivo.
Cholesterol-dependent cytolysins (CDCs) represent a family of homologous pore-forming proteins secreted by many Gram-positive bacterial pathogens. CDCs mediate membrane binding partly through a conserved C-terminal undecapeptide, which contains a single cysteine residue. While mutational changes to other residues in the undecapeptide typically have severe effects, mutating the cysteine residue to alanine has minor effects on overall protein function. Thus, the function of this highly conserved reactive cysteine residue remains largely unknown. We report here that the CDC Listeriolysin O (LLO), secreted by the facultative intracellular pathogen Listeria monocytogenes, was post-translationally modified by a S-glutathionylation at this conserved cysteine residue, and that either endogenously synthesized or exogenously added glutathione was sufficient to form this modification. When recapitulated with purified protein in vitro, this modification completely ablated the activity of LLO, and this inhibitory effect was fully reversible by treatment with reducing agents. A cysteine-to-alanine mutation in LLO rendered the protein completely resistant to inactivation by S-glutathionylation and retained full hemolytic activity. A mutant strain of L. monocytogenes expressing the cysteine-to-alanine variant of LLO was able to infect and replicate within bone marrow-derived macrophages indistinguishably from wild-type in vitro, yet was attenuated 4-6 fold in a competitive murine infection model in vivo. This study suggests that S-glutathionylation may represent a mechanism by which CDC family proteins are post-translationally modified and regulated, and help explain an evolutionary pressure behind the highly conserved undecapeptide cysteine.
Luo, Wenyi. "Identification and characterization of virulence factors of mycoplasmas." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2010p/luo.pdf.
Повний текст джерелаRashid, Rebecca Ann. "Expression of virulence factors in pathogenic Escherichia coli /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/11512.
Повний текст джерелаForslund, Anna-Lena. "Identification of new virulence factors in Francisella tularensis." Doctoral thesis, Umeå universitet, Molekylärbiologi (Teknat- och Medfak), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-30857.
Повний текст джерелаHouston, Simon Andrew. "Molecular genetic analysis of Bacteroides fragilis virulence factors." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491954.
Повний текст джерелаWang, Qinning. "Erysipelothrix rhusiopathiae : epidemiology, virulence factors and neuraminidase studies." University of Western Australia. Microbiology Discipline Group, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0043.
Повний текст джерелаPaterson, Gavin Kirkwood. "Identification and characterisation of novel pneumococcal virulence factors." Thesis, University of Glasgow, 2003. http://theses.gla.ac.uk/3576/.
Повний текст джерелаShami, Khosrow. "Virulence factors of Helicobacter pylori : a fermentation study." Thesis, University of Westminster, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323129.
Повний текст джерелаRidha, Ghalib Swadi Abdul. "Virulence and associated factors in porcine Escherichia coli." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237528.
Повний текст джерелаAllen, Richard Charles. "Secreted virulence factors : evolution, ecology and therapeutic manipulation." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25789.
Повний текст джерелаPrasad, Joni M. "Hemostatic Factors in Bacterial Virulence and Host Defense." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1329495133.
Повний текст джерелаLucas, Erynn Ainslee. "Identification and Characterization of Arcanobacterium haemolyticum Virulence Factors." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/193896.
Повний текст джерелаAu, Candy Po Yee. "Haemolytic virulence factors in Photorhabdus luminescens strain W14." Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413130.
Повний текст джерелаAgena, Mahmoud B. "Neonatal exposure to pathogens : determining key virulence factors." Thesis, Nottingham Trent University, 2017. http://irep.ntu.ac.uk/id/eprint/32859/.
Повний текст джерелаWawrzyniak, Ivan. "Génomique et post-génomique du parasite intestinal Blastocystis sp. sous-type 7. Evaluation de son pouvoir pathogène." Thesis, Clermont-Ferrand 2, 2012. http://www.theses.fr/2012CLF22243/document.
Повний текст джерелаBlastocystis spp. is a highly prevalent anaerobic Stramenopile parasite found in the intestinal tract of humans and various animals. This parasite is associated with non specific intestinal disorders, and could be involved in functional disorders such as the irritable bowel syndrome (IBS). In this work, the Blastocystis sp. ST7 genome sequencing project was carried out in collaboration with the Génoscope of Evry, the National University of Singapore, the Pasteur Institute of Lille and the University of Provence. This genome consists in a nuclear genome of 18,8 Mpb encoding 6020 genes, and a mitochondria‐like genome of 29 kpb localised in the mitochondrion‐like organelles. The analysis of this genome brings information about the evolution of this micro‐organism, its adaptation to the intestinal environment and its potential virulence factors. Blastocystis sp. ST7 was predicted to harbor several genes coding proteins that could act at the parasite‐host interface, and that are known to be involved in the pathogeny of many protozoa. They are PKS, NRPS, and hydrolases among them proteases. In addition, proteolytic activities were highlighted in the parasite culture supernatants. Two cysteine proteases (a cathepsin B and a legumain) were identified and characterized from the supernatants and could play a role in the physiopathology of the parasite, that confirm our in silico analyses. This work opens new ways to evaluate the impact of this parasite in human health
Gunther, Erik Christian. "Molecular mechanisms of brain derived neurotrophic factor secretion and action /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/5086.
Повний текст джерелаTalagrand, Emilie. "Diversité, complexité et adaptation au comportement pathogène au sein du genre Aeromonas." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT123/document.
Повний текст джерелаAeromonas groups ubiquitous bacteria mainly living in aquatic environments. These opportunistic pathogens for human and numerous animals have a large repertoire of virulence-associated factors. Although pathotypes were proposed and despite some species are more frequently isolated in human and animal infections, their pathogenicity is still poorly understood, mostly because very few comprehensive functional studies are available and because investigations taking into account the genetic diversity and the biological complexity within the genus are lacking.We assumed that for an opportunistic bacterial pathogen of environmental origin as versatile and ubiquitous as Aeromonas, the population structure in complex of species, the outstanding genetic/genomic diversity, the polymorphism of virulence factors and the interactions within pathogenic populations can act as factors driving the adaptation to a pathogenic behaviour. To test this hypothesis, we studied i) the diversification within “A. media”, a complex of species used as a model by a population study that included multilocus genetics, phylogenetics, evolutionary features, comparative genomics, as well as phenotypics, lifestyle and habitat ii) the patho-genomics of well-known virulence factors in aeromonads (aerolysin, thermolabile and thermostable enterotoxins, exotoxin A, serine protease, components and effectors of type III secretion system, and lateral flagellin) in a population that is representative of the known taxonomic diversity in the genus (30 species) and iii) the pathogenic behaviour using an in vivo model (Caenorhabditis elegans), an in vitro model (cytotoxicity, cytoadhesion, biofilm production, motility), and intercellular signals production (type I quorum-sensing) for populations involved in mixed aeromonosis, i.e. 5% of human aeromonosis defined by the isolation of at least 2 distinct clones.The phenomenon of speciation described in the complex “A. media” that aggregates 3 genomic species demonstrates that Aeromonas harbours a population structured in complexes of closely related species whose genetic and genomic diversity, as well as evolution mode (mutations and recombinations) reveal a wide adaptative and patho-adaptative potential linked to lineage emergence. Among the complex “A. media”, the species A. rivipollensis seems to be more adapted to a host-associated lifestyle and harbours specific genes for the resistance to environmental stress. Aeromonas has a wide range of virulence-associated genes, which presented diverse evolutive history. Some of them display a phylogeny linked to the core-genome evolution. These results suggest that these genes are involved in speciation processes probably related to niches adaptation. The evaluation of performances of virulence PCRs revealed major lacks of sensitivity of tested methods mainly due to the genetic polymorphism of the virulence factors. By using in vivo models and in vitro models, we also showed that Aeromonas mixed populations recovered from clinical samples could change the course of infection, likely through a cooperative or competitive mechanism that involves cell-to-cell signalling.The high complexity of Aeromonas results from its population structure, virulence factors polymorphism and multicellular behaviours. They are all putative adaptation factors to a pathogenic behaviour that may explain at least partially the difficulties encountered to elucidate pathogenicity of these bacteria
Georgiades, Kalliopi. "Phylogénomique des bactéries pathogènes." Thesis, Aix-Marseille 2, 2011. http://www.theses.fr/2011AIX20690/document.
Повний текст джерелаThe virulence of pathogenic bacteria has been attributed to virulence factors and pathogenic bacteria are considered to have more genes compared to bacteria that do not cause disease. According to the first genomic studies, removing a certain number of genes from pathogenic bacteria impairs their capacity to infect hosts. However, more recent studies have demonstrated that the specialization of bacteria in eukaryotic cells is associated with massive gene loss, especially for allopatric endosymbionts that have been isolated for a long time in an intracellular niche. Indeed, bacteria living in sympatry often have bigger genomes and exhibit greater resistance and plasticity and constitute species complexes rather than true species. Specialists, including specific pathogenic bacteria, escape these bacterial complexes and colonize a niche; thereby gaining a species name. Their specialization allows them to adopt allopatric lifestyle and experience reductive genome evolution. These observations led us to design a study to quantify the rate of gene losses during the evolution of free-living bacteria to intracellular specialists. Our objective was to verify that what characterizes the evolution of intracellular bacteria is genomic reduction, taking under consideration all possible gene gain events. Furthermore, in another neutral study comparing the 12 most dangerous pandemic bacteria to Humans to their closest non-epidemic species, we wished to identify any genomic specificities associated to the virulent capacity of pathogenic bacteria and demonstrate that, besides toxins and surprisingly, toxin-antitoxin modules, pathogenic bacteria are not characterized by more virulence factors, but rather by a loss of regulatory genes. Finally, virulent bacteria exhibit a genomic repertoire in which absent genes are as important as present ones
Bernardi, Adilson César Abreu. "Estudo de amostras de Staphylococcus coagulase-negativa quanto a formação de biofilme /." Araraquara : [s.n.], 2005. http://hdl.handle.net/11449/103991.
Повний текст джерелаBanca: Isabel Yoko Ito
Banca: Sérgio Aparecido Torres
Banca: Maria de Lourdes Ribeiro de Souza
Banca: Clarice Queico Fujimura Leite
Resumo: Os Staphylococcus coagulase-negativa, particularmente, os Staphylococcus epidermidis são a causa mais freqüente de infecções relacionadas ao cateter por sua habilidade em aderir a uma superfície e entre si (aderência intercelular) formando biofilme em multicamadas sobre superfícies de polímeros. O objetivo do presente estudo foi avaliar cepas hospitalares de Staphylococcus coagulasenegativa isoladas de cateteres intravenosos, quanto à resistência a oxacilina, produção de slime, aderência ao poliestireno, habilidade de formar biofilme sobre superfícies abióticas (cateter esterilizado) e a presença de genes icaAD. Na presente pesquisa, a presença de icaA e icaD foi determinada pelo método PCR, em uma coleção de 27 amostras Staphylococcus coagulase-negativa (10 Staphylococcus epidermidis, 4 S. haemolyticus, 2 S. hominis, 2 S. lugdunensis, 1 S. saprophyticus, 1 S. schleiferi, 2 S. xylosus e 4 S. warneri). Os genes icaAD foram detectados em dez cepas S. epidermidis... (Resumo completo, clicar acesso eletrônmico abaixo)
Abstract: Coagulase-negative Staphylococcus, particularly, Staphylococcus epidermidis are frequent cause of infections associated with catheters and is attributed to the attachment ability on a surface and each other (intercellular adhesion) forming a multilayered biofilm on polymeric surfaces. The objective of the present study was to evaluate coagulase-negative Staphylococcus strains isolated from intravenous catheters by oxacillin resistance, slime production (qualitative method) and spectrophotometric assay (quantitative method), ability to form biofilm on abiotic surfaces (steriled catheter) and the presence of icaAD genes. In the present study icaA and icaD were determined by PCR method, in a collection of 27 coagulasenegative Staphylococcus (10 Staphylococcus epidermidis, 4 S. haemolyticus, 2 S. hominis, 2 S. lugdunensis, 1 S. saprophyticus, 1 S. schleiferi, 2 S. xylosus and 4 S. warneri). The icaA genes were detected in nine S. epidermidis and icaD in ten. The slime-producing ability was determined by culture on Congo red agar plates in which slime-producing strains formed black colonies in 10 S. epidermidis, 4 S.haemolyticus, 4 S. warneri, 2 S. xylosus and 1 S. chromogenes, while nonslimeformingones develop red colonies. The quantitative assay of coagulase-negative Staphylococcus was observed in 19 strains, including: 10 S. epidermidis, 3 S.haemolyticus, 3 S. warneri, 2 S. xylosus, 1 S. chromogenes. The ability of coagulasenegative Staphylococcus to form biofilm embedded in an amorphous substance wasobserved by scanning electronic microscope on abiotic surface in 10 S. epidermidis,3 S. haemolyticus, 2 S. hominis, 2 S. lugdunensis, 1 S. saprophyticus, 1 S. schleiferi,2 S. xylosus and 3 S. warneri. The oxacillin resistance was observed in 9 strains S.epidermidis, 3 S. haemolyticus, 3 S. warneri, 1 S. xylosus and 1 S. chromogenes. All strains of staphylococci were susceptible... (Complete abstract, click eletronic address below)
Doutor
Molinos, Abós Sònia. "Noves aproximacions als estudis d’epidemiologia molecular i al diagnòstic de les infeccions causades per Staphylococcus aureus. Aportacions al coneixement dels factors de virulència i patogenicitat." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/368219.
Повний текст джерелаIn recent decades, Staphylococcus aureus has become an important human pathogen causing a wide variety of diseases, ranging from uncomplicated infections to life-threatening septicaemia, thus leading to significant morbidity and mortality. This thesis recorded clinical and epidemiological characteristics from patients with S.aureus infections, especially bacteremia and skin-soft tissue infections as well as microorganism related factors. The second aim was to investigate the molecular typing and to characterize the virulence factors of S. aureus isolates and some phenotypic assays for its measurement. A total of 293 patients with bacteremia were included. Phage typing allowed to type the 37.5 % of MRSA strains and 43.3 % of MSSA. Regarding molecular characterization, mecA was detected in 28 strains, in accordance with the data of antibiotic susceptibility testing by microdilution method. SCCmec typing of SARM isolates showed that 27 of these were carrying SCCmecIVc and only in one case was found SCCmec IVa and ACME negative. Spa typing revealed the prevalent clonal complex CC002 (31%), enclosing two predominant spa types: t002, t067 in MSSA while the clonal complex CC067 (37.14%) including spa types t0067 and t002 was the predominant in MRSA strains. Genotyping by pulsed-field gel electrophoresis of these SARM strains grouped into two genotypes, E7 and E8. These profiles are the predominant clones in Spain. The application of microarrays for genotyping reflected that the most frequent CC was CC5 (38.2%) followed by CC30 (21.6%). Concerning the agr types, most isolates presented agr II (46.1%). Increased frequency of bacteraemia and maintenance of mortality rates are related to the susceptibility of the host, strain-specific features, epidemiological characteristics and the time from microbiological diagnosis to the starting of appropriate antibiotic treatment. The study of three diagnostic methods: BinaxNow S.aureus /MRSA PBP2, MicroPhage MRSA/ MSSA Blood Culture Test and GenomEra MRSA /SA Blood Culture for the direct identification and susceptibility S. aureus testing directly from positive blood cultures, allowed the early administration of appropriate antibiotic treatment in 79.25% of the cases. The origin of the bacteraemia was nosocomial in 58’4% of the cases and 45.7% were catheter related. Comorbidities were present in 80% of patients, being the most frequent neoplasia (35.5%), followed by diabetes mellitus (30.4%), end stage renal disease (14%) and immunosuppressive treatment (13.7%). Development of complications was present around 25% of the cases, and 8.5% of patients developed persistent bacteraemia. On the other hand, Community-Acquired methicillin resistant Staphylococcus aureus (CA-MRSA) causes approximately 20% of skin-soft tissue infections. A specific clone of CA-SARM, USA300-ST8-SCCmec IVc and characteristically lacking the ACME was the most prevalent in our environment, similar to USA300 (USA300-ST8-SCCmec Iva). We did not find any association between strain characteristics and nationality of the patients. All our patients presented an uncomplicated infection, both when MSSA and MRSA. In our study we reported a high prevalence of Panton Valentine leukocidin (PVL) producers among MSSA and MRSA and all patients presented a favourable outcome even though inappropriate antibiotic treatment was prescribed empirically. It is considered that the treatment of choice for these infections, irrespective of antibiotic susceptibility, is incision and drainage. The real pathogenic role of PVL it is still a subject of controversy, arising from results obtained from clinical studies.
Buchan, Blake Wade Jones Bradley D. "Examining the regulation of virulence factors in Francisella tularensis." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/341.
Повний текст джерелаSolomonson, Matthew Morris. "Structure, proteolysis, and evolution of secreted tuberculosis virulence factors." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54572.
Повний текст джерелаMedicine, Faculty of
Biochemistry and Molecular Biology, Department of
Graduate
Sharp, Jacqueline. "The culture, epidemiology and virulence factors of Clostridium difficile." Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/26927.
Повний текст джерелаVasi, József. "Characterization of two potential virulence factors in Streptococcus dysgalactiae /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2000. http://epsilon.slu.se/avh/2000/91-576-5758-0.pdf.
Повний текст джерелаJohansson, Linda. "Host responses and bacterial virulence factors in Neisseria infections /." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-017-6/.
Повний текст джерелаHolmes, Ashleigh. "Characterising virulence factors from pathogenic bacteria using fluorescent reporters." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3317/.
Повний текст джерелаGrant, Kathleen Ann. "Genetics and biochemistry of potential virulence factors of Campylobacter." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270422.
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