Properties of Shiga toxin-producing Escherichia coli (STEC) isolates from sheep in the State of São Paulo, Brazil.

Fecal samples from 48 sheep from two farms in São Paulo, SP, Brazil, were examined to determine the prevalence of Shiga toxin-producing Escherichia coli (STEC). Forty-two STEC strains were isolated from 25 (52.1%) of 48 sheep feces, and were examined for the presence of genes encoding STEC-related virulence factors. Twenty-one (50.0%) of the 42 STEC isolates were positive for stx(1) and stx(2), 16 isolates (38.1%) were stx(1), and five (11.9%) were stx(2). Expression of Shiga toxins was demonstrated by the Vero cell toxicity test for all the strains carrying stx. Fourteen of the STEC strains (33.3%) carried the enterohemolysin gene (ehly) and presented the enterohemolytic phenotype, and five (11.9%) were positive for the plasmid encoded katP gene. The eae gene was not present in any of the isolates. STEC strains presenting stx(1), stx(2) and ehly were most commonly (23.8%) recovered from these sheep. The predominant STEC serotype found was ONT:H8, and others included O5:H-, O16:H-, O75:H-, O75:H8, O87:H16, O91:H-, O146:H21, O172:H-, OR:H-, ONT:H- and ONT:H16. This is the first report on ovine STEC in South America, and identifies a number of ovine non-O157 STEC that belong to serotypes implicated in human disease.