Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Role of newly identified candidate genes in the pathogenesis of AEEC in rabbits

Weaned rabbit is a relevant non-human host for study in vivo EPEC and to a lesser extent EHEC pathogenesis. Several rabbits EPEC serotypes, such as O103:H2 and O26:H11, induced severe and lethal diarrhoea upon oral inoculations with as few as 104 CFU. The objective of this WP is to compare a wild-type pathogenic E. coli strain with different isogenic mutants in experimental rabbit infections. This approach was first used to analyse newly described putative virulence factor such as EspF, Paa, and Orf31 and was then extended to other putative contributor genes that were identified in WP05, 06, 07, 14 and 15.

Major finding during the project:

We have constructed null mutants in new identified genes as for example cif (see WP05) or in genes involved in the secretion as for example escN and in the regulation of the LEE as for example hha. We have then constructed null mutants in cdt, fliC and in orf16 from the LEE.

Total DNA preparations from strains resulting from this procedure has been restricted and probed to confirm the allelic exchange. All the mutant resulted from a double crossing-over except. Western-blots and FAS or CPE assays have been performed to verify the loss of the putative virulence trait. The mutant strain have been then complemented with the wild type allele of the gene to establish that no other genes have been affected during the allelic exchange.

We then have compared the ability of wild type and defined mutant strains to induce enteropathogenic responses in rabbits. However, to reduce the number of infected (and eventually killed) rabbits, we mainly used the rabbit ileal loop model to analyse the enteropathogenic response. Except when we muted the TTSS, tir or eae (intimin), none of the tested mutants has a significantly reduced virulence in the rabbit model.

Reported by

INRA-ENVT Microbiologie
23 chemin des Capelles
31000 Toulouse
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