Detection and characterization of verocytotoxin-producing Escherichia coli (vtec) O157 and non-O157 in cattle at slaughter.

Between September 2001 to June 2002, 145 samples of bovine caecal content were collected at slaughter for verocytotoxin-producing Escherichia coli (VTEC) serogroups O157 and non-O157 detection. For E. coli O157 the immunomagnetic-separation technique was performed. The enterohaemolytic phenotype was the target for non-O157 VTEC identification. The vero cell assay (VCA) was performed for toxic activity detection. The genomic sequence for VT1, VT2 and intimin (vt1, vt2, eae genes) were identified by PCR analysis. Eight VTEC O157 and eight non-O157 VTEC isolates were detected. VTEC O157, eae-positive strains were shed by 9.7% of feedlot cattle and by 2.5% of dairy cows. Non-O157 VTEC, eae-negative isolates were detected in the intestinal content of 12.5% dairy cows and of 2.1% feedlot cattle. VTEC-shedding cattle came from 18.1% of the farms included in the study. From cattle faeces, VTEC O91:H- (VT2-positive, eae-negative), responsible of human diarrhoeal disease in Europe, was recovered. Other VTEC serogroups identified in the present study were O74, O109, O110, O116, and O117.