Production de Shiga-toxine Stx2 par les Escherichia coli entérohémorragiques: influence du génotype stx2, régulation par le quorum sensing et le microbiote intestinal

Abstract : Enterohemorrhagic Escherichia coli are food poisoning pathogens causing hemorrhagic colitis and hemolytic and uremic syndrome. Their main virulence factors are Shiga toxins (Stxs), especially Stx2. In this work we first studied a subset of strains from different origins belonging to different seropathotypes and expressing different stx2 variants. We found that the most pathogenic strains O157: H7 express the stx2 variant and produce high levels of Stx2 in basal as well as in induced conditions. Non-O157:H7 strains showing the same properties could be dangerous for human health. We also investigate the effect of molecules found in the gastrointestinal tract on Stx2 synthesis. Nor quorum sensing autoinducers AI-2 and AI-3 produced by th intestinal microbiota neither the intestinal neuroendocrine hormone norepineprine influence Stx2 synthesis. However, the protein regulator QseA involved in quorum sensing signalling pathway could be a transcriptional activator of stx2. Finally, we studied Stx2 production by the O157:H7 strain EDL 933 in culture medium mimicking the living conditions of EHEC in the gut by using a human flora associated rat model. We show that the human microbiota transcriptionally inhibits Stx2 synthesis through transcriptional inhibition of recA. This inhibition can be partially attributed to the intestinal species Bacteroides thetaiotaomicron.
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Contributor : Saltet de Sablet Thibaut <>
Submitted on : Tuesday, August 10, 2010 - 11:52:25 PM
Last modification on : Tuesday, May 23, 2017 - 11:24:12 AM
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Saltet de Sablet Thibaut. Production de Shiga-toxine Stx2 par les Escherichia coli entérohémorragiques: influence du génotype stx2, régulation par le quorum sensing et le microbiote intestinal. Biochimie [q-bio.BM]. Université Blaise Pascal - Clermont-Ferrand II, 2007. Français. ⟨tel-00509224⟩

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