Biochemical Features and Virulence Gene Profiles of Non-O157/O26 Enterohemorrhagic Escherichia coli Strains from Humans in the Yamaguchi Prefecture, Japan.

The biochemical features and virulence gene profiles of 37 enterohemorrhagic Escherichia coli (EHEC) strains belonging to serogroups other than O157 and O26 (non-O157/O26 EHEC) were investigated. All strains were isolated from humans between 2002 and 2013 in the Yamaguchi Prefecture. Serogroup O111 strains were the most common, followed by O103, O121, and O145. Most strains (84%) were negative for sorbose fermentation, whereas only 1 and 2 were negative for sorbitol and rhamnose fermentation, respectively. Two strains lacked β-D-glucuronidase activity. Shiga toxin (stx) subtyping revealed 6 genotypes:stx1a (n = 20), stx1a + stx2a (n = 8), stx2a (n = 4), stx2b (n = 3), stx2a + stx2c (n = 1), and stx2a + stx2d (n = 1). Polymerase chain reaction screening of other toxin and adherence genes showed that astA, subA, and cdtB were present in 5, 2, and 2 strains, respectively. The intimin gene eae was present in 30 strains (81%). Of the 7 eae-negative strains, saa and eibG were found in 3 and 2 strains, respectively; no adherence factors were detected in the remaining 2 strains. The antimicrobial susceptibility profiles of the strains to 12 drugs were examined and 11 strains (30%) showed resistance to 1 or more drugs. Our results revealed that non-O157/O26 EHEC strains exhibit various biochemical phenotypes and carry several toxins and adherence factor genes.