MOLECULAR EPIDEMIOLOGY Clonal structure of Shiga toxin (Stx)-producing and -D-glucuronidase-positive Escherichia coli O157:H7

A total of 22 clonal phenotypic variants of Shiga toxin (Stx)-producing Escherichia coli (STEC) O157:H7 was isolated from six different locations in Hokkaido, Japan. These isolates were negative for sorbitol fermentation but positive for -D-glucuronidase (GUD). They carried eaeA, EHEC-hlyA, pas and etpD genes like typical E. coli O157:H7 and, in addition, stx1 and stx2 genes. However, they were shown to lack katP and espP genes that are present in typical STEC O157:H7. All these atypical GUD STEC O157:H7 isolates had very similar antimicrobial susceptibilities. Pulsed-field gel electrophoresis analysis with XbaI, SfiI, SwaI, SpeI and NotI indicated that they were identical or closely related to one another. From their phenotypic and genotypic features, these GUD STEC O157:H7 isolates may represent a distinct clone among STEC O157