Prevalence and characteristics of Shiga toxin-producing Escherichia coli from healthy cattle in Japan

The prevalence of Shiga toxin-producing Escherichia coli (STEC) in Japan wa s examined by using stool samples from 87 calves, 88 heifers, and 183 cows on 78 farms. As determined by screening with sh-PCR, the prevalence was 46% in calves, 66% in heifers, and 69% in cows; as determined by nested stx-PC R, the prevalence was 100% in all animal groups. Of the 962 isolates picked by colony sa hybridization, 92 isolates from 54 farms were characterized t o determine their O serogroups, virulence factor genes, and antimicrobial r esistance. Of these 92 isolates, 74 (80%) could be classified into O serogr oups; 50% of these 74 isolates belonged to O serogroups O8, O26, O84, O113, and O116 and 1 isolate belonged to O serogroup O157. Locus of enterocyte e ffacement genes were detected in 24% of the isolates, and enterohemorrhagic E. coli (EHEC) hlyA genes were detected in 72% of the isolates. Neither th e bundle-forming pilus gene nor the enteropathogenic E. coli adherence fact or plasmid was found. STEC strains with characteristics typical of isolates from human EHEC infections, which were regarded as potential EHEC strains, were present on 11.5% of the farms.