Clonal structure and pathogenicity of Shiga-like toxin-producing, sorbitol-fermenting Escherichia coli O157:H-.

We compared a collection of sorbitol-fermenting (SF) Escherichia coli O157:H- strains with SF E. coli O157:H45 and non-SF E. coli O157:H7 and E. coli O157:H- strains by pulsed-field gel electrophoresis. The SF E. coli O157:H- strains had identical or closely related XbaI patterns that differed markedly from those for the other E. coli O157 strains. Plasmid content and the presence of Shiga-like toxin-converting phages were determined for the SF E. coli O157:H- strains, indicating that these strains harbor a single 90-kb plasmid. They are lysogenized by toxin-converting phages and harbor the eae gene. Nonmotile E. coli O157 strains were observed to adhere more efficiently to HEp-2 cells than the motile strains. From their phenotypic and genotypic features, the SF E. coli O157:H- strains may well represent a new clone with non-SF E. coli O157:H7 pathogenic characteristics.