Detection and Characterization of Enterohaemorrhagic Escherichia coli in Slaughtered Cattle

Abstract

Fecal samples from slaughtered cattle were studred for enterohaemorrhagic E&vichia co/i (EHEC) by DNA hybridization with biotin-labelled DNA probes specific for the EHEC virulence plasmid, Shigalike toxin I (SLT I), Shiga-like toxin I1 (SLT 11) and eae gene. Among 136 animals analysed, 47 (34.5%) were found to carry EHEC. The cytotoxic genotypes observed for EHEC strains were: 60.4% SLT I, 12.5% SLT I1 and 10.4% SLT I+SLT 11; 16.7% resulted SLT I and SLT I1 negative. A total of 14 out of 48EHEC strains (29.2%) hybridzed with a fimbrial probe and 14 of 48 strains with an em probe. An important number of strains (18 out of 48) belonged to serogroups 0157,026 and 01 11, serogroups also commonly isolated from haemolytic uremic syndrome cascs in Chile. While EHEC isolates from the same animal were usually of the same serogroup, one animal was found to carry two EHEC strains of drfferent serogroups. A total of 50'Yn of EHEC strains were sorbitol negative, irrespective of the 0 serogroup or EHEC genotypic profile. Results obtained in this study strongly suggest that cattle in Chile are a reservoir of EHEC associated with disease in humans.