CHAPITRE 1 - Université de Bourgogne

Abstract
Enterohemorrhagic Escherichia coli (EHEC) are an important subset of Shiga toxin–
producing E. coli (STEC) associated with foodborne infections. These bacteria can cause
hemorrhagic diarrhoeal disease and Haemolytic and Uremic Syndrome which are associated
with some predominant serotypes defined by AFSSA institute: O26, O103, O111, O145 and
O157.
Cattle are the primary reservoir of STEC. Although STEC transmission to humans is
frequently associated with consumption of meat, dairy products have also been implicated in
human cases. Sensitive and rapid detection methods for STEC are essential for the food
industry to ensure a safe food supply. However, the detection of STEC in foods is problematic
because it’s an heterogeneous group which displays a broad range of both genotypic and
phenotypic differences.
The aim of this PhD work was to optimize the research protocol of STEC strains in food in
order to provide some protocols to the industries for improving risk management protocol.
We choosen to study different steps of the protocol: The first one was the enrichment of E.
coli O26 allowing their detection in raw milk cheeses after 24 h enrichment in EPT+
acriflavine + cefixime-tellurite. Then, we evaluated the VIDAS ECPT UP performances’ for
the detection of E. coli O157: H7 in raw ground beef. Through this study, we showed the
ability to reduce enrichment time for sample analysis of 25g (6h) and the feasibility of
analyzing samples of 375g with a sample to broth ratio of ¼ after 24h enrichment. Thereafter
we looked at the confirmation step. We developed and optimized automated VIDAS immuno-
concentration of E. coli O157, O26, O103, O111 and O145 (VIDAS ESPT) with the use of
recombinant phage proteins for capture.
Keywords: STEC, food, detection, pathogenic.
SOMMAIRE
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