P-071. Prevalence of Shiga Toxin Producing Escherichia coli (STEC) in Frozen Minced Beef in France

C. Mazuy-Cruchaudet1, C. Bavai1, M. Poirel1, C. Taillandier1, L. Giuliani2, C. Vernozy-Rozand1;
1ENVL, Marcy l'Etoile, FRANCE, 2DGA, Paris, FRANCE.

Background- Shigatoxin producing Escherichia coli (STEC) are important food-borne pathogens in humans. The aims of the present study were to determine STEC prevalence in frozen minced beef in France and to characterize the STEC strains isolated (virulence genes and serotype). Methods- 3354 minced beef samples were analyzed. The detection of stx genes was performed by polymerase chain reaction (PCR). In addition, a second PCR specific for E. coli O26 or O103 or O111 or O145 detection was carried out on the stx-positive samples. STEC strains were recovered from positive samples by immuno-concentration (IMS). Then the strains isolated were genetically characterized (stx1, stx2, eae and hlya). An automated enzyme-linked fluorescence immunoassay (ELFA), the VIDAS E. coli O157 method, was used to detect E. coli O157 serogroup from the stx-positive samples. The isolation of E. coli O157:H7 from positive sample with the VIDAS was performed using an automated immunoconcentration (ICE) system. Then the strains isolated were genetically characterized (stx1, stx2, eae and hlya). Results- 964 out of 3354 (28.7%) minced beef samples analyzed were PCR stx + and 172 were both PCR eae + and stx+. Among these 172 samples,121 samples were proved to be positive by PCR for the research of the serogroups: 62 positive for O103, 21 positive for O157, 16 positive for O26, 14 positive for O145 and 8 positive for O111. Eleven strains of STEC were isolated: 5 E. coli O157:H7, 3 E. coli O103, 2 E. coli O26 and 1 E. coli O111. Twenty other strains were isolated: 13 E. coli O103, 8 E. coli O26, 1 E. coli O145. All of them were not pathogenic according to the definition given by the French Food Safety Agency. Conclusion-The results of this study did not differ greatly from those reported in other countries with regard to the prevalence of O157 in minced beef. However we must keep on mind that serotypes different from O157:H7 also played an important role in minced beef contamination.