Molecular epidemiological study of a mass outbreak caused by enteropathogenic Escherichia coli O157 : H45

We made a molecular analysis of O157:H45 Escherichia coli isolated from a m ass outbreak that occurred in Obihiro City, Using DNA analysis, we confirme d this infection case as a mass outbreak. Although the isolates expressed O 157 antigen, they did not produce Vero toxin. We concluded they were entero pathogenic E. coli (EPEC) because they had a bfp gene and an EAF plasmid, a nd further they exhibited local adherence to HEp-2 cells. We believe this i s the first report of a mass outbreak by O157 EPEC, and we suggest that PCR using eae- and bfp-specific primers and HEp-2 adherence assay are useful t o identify EPEC.