Phenotypic and molecular analysis of tellurite resistance among enterohemorrhagic Escherichia coli O157:H7 and sorbitol-fermenting O157:NM clinical isolates.

A total of 66 (98.5%) of 67 enterohemorrhagic Escherichia coli (EHEC) O157:H7 strains had increased potassium tellurite (Te) MICs (32 to 1,024 microg/ml), grew on Te-containing media, and possessed Te resistance (ter) genes, whereas 83 (96.5%) of 86 sorbitol-fermenting (SF) EHEC O157:NM strains had Te MICs of </=4 microg/ml, did not grow on Te-containing media, and lacked ter genes. Optimal detection of SF EHEC O157:NM strains requires Te-independent strategies.