ATYPICAL STRAINS OF VEROCYTOTOXIN-PRODUCING ESCHERICHIA-COLI O157 IN BEEF-CATTLE AT SLAUGHTER IN VENETO REGION, ITALY

Cattle arriving for slaughter at abattoirs in the Veneto region of N. Italy were examined for intestinal carriage of Escherichia coli O157. Rectal swabs were cultured in modified buffered peptone water and E. c oli O157 was concentrated by an immunomagnetic separation technique; t he magnetic beads were cultured onto cefixime tellurite sorbitol MacCo nkey agar. Sorbitol non-fermenting E. coli O157 was isolated from 15 ( 3.6 %) of 419 feedlot cattle but not from 437 veal calves or 65 culled cows. All strains of E. coli O157 hybridized with DNA probes specific for the VT1 or VT2 genes, but two strains did not produce toxin detec table by Vero cell assay. Six different plasmid profiles were observed with all strains harbouring the large 93 kb plasmid characteristic of VTEC. Six strains produced urease but otherwise strains were biochemi cally typical of E. coli O157. One strain was resistant to streptomyci n, tetracycline and sulphonamides but the remainder mere sensitive to all antimicrobials tested. This is the first description of the isolat ion of verocytotoxin-producing E. call O157 from cattle in Italy. As t he contamination of bovine carcasses with E. coil O157 during slaughte r and processing has been demonstrated, the risk of transmission of th is organism from beef cattle to the human population in the Veneto reg ion, through foods of bovine origin or by other routes, should not be overlooked.