Characterization of stx2 and its variants in Escherichia coli O157:H7 isolated from patients and animals

Abstract

In this study, we investigated 72 Escherichia coli O157:H7 strains from humans and animals to determine stx 2 and its variants by polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism. Most isolates were found to carry stx 2 or its variants and the stx 2c was the dominant subtype; for the prevalence of stx 2c in stx 2 -positive isolates was 89.6% (42/47). All stx 2 and stx 2c harboring isolates obtained from humans had caused diarrhea or hemolytic-uremic syndrome. Three strains isolated from a piglet and two cattle carried the stx 2c gene with an IS1203v inserted sequence. Sequencing of this region revealed that, this 1.3 kb insertion was very similar to a previously identified IS 1203v sequence and the insertion interrupted the carboxyl end of the B subunit coding region of stx 2c gene. The corresponding positions in the stx 2c gene sequence in which the IS 1203v sequence was inserted was varied. The isolates possessing IS1203v were inactive in the Vero cell toxicity assay.