Serotypes and virulence genes of ovine non-O157 Shiga toxin-producing Escherichia coli in Switzerland

Sixty ovine STEC strains were examined with the aim (i) to serotype the strains, (ii) to characterize virulence factors, and (iii) to discuss possible associations between these factors and to assess the potential pathogenicity of these strains for humans. The 60 sorbitol-positive, non-O157 STEC strains belonged to 19 O:H serotypes, whereas 68% were of five serotypes (O87:H16, O91:H-, O103:H2, O128:H2, O176:H4). 52% belonged to serotypes reported in association with HUS. Five serotypes were not previously reported in sheep strains. Of the 47 strains encoding for stx1 variants, 57% were stx1c- and of the 45 encoding for stx2 variants, 80% were stx2d-positive. Eighty-two percent of the strains showed further putative virulence factors: 13% were eae-, 60% ehxA- and 67% saa-positive. The associations between harboring (i) eae and stx1, stx2, ehxA or no saa and (ii) saa and stx1c or stx2d were significant ( P