Detection and genetical characterization of shiga toxin-producing Escherichia coli from wild deer

Shiga toxin (Stx)-producing Escherichia coli (STEC) strains isolated from w ild deer in Japan were examined. A total of 43 fecal samples were collected 4 times from 4 different sites around Obihiro City, Hokkaido, Japan, in Ju ne and July 1997, Seven STEC strains were isolated by PCR screening, all of them were confirmed by ELISA and Vero cell cytotoxicity assay to be produc ing only active Stx type 2 (Stx2), Moreover, they seemed to carry the hemol ysin and eaeA genes of STEC O157:H7, and some isolates harbored large plasm ids which were similar to the 90-kilobase virulence plasmid of STEC O157:H7 , Based on their plasmid profiles, antibiotic resistance patterns, PCR-base d DNA fingerprinting data obtained by using random amplified polymorphic DN A (RAPD) and the stx(2) gene sequences, all isolates were divergent from ea ch other except for 3 isolates from the first and second samplings. A DNA s equence analysis of representative isolates revealed that deer originating STEC strains were closely related to each other, but not to the Stx2-produc ing STEC strains isolated from a mass outbreak in Obihiro at the same time. A phylogenic analysis of the deduced Stx2 amino acid sequences demonstrate d that three distinct clusters existed in the deer originating STEC strains and that the Stx of deer originating STEC was closely associated with that originating from humans, but not those of STEC originating from other anim als. These results suggest that STEC contamination of deer carcasses should be considered as a potential source of human infection and adequate sanita ry inspection of meat for human consumption is also essential for wild anim als.