CLONAL RELATEDNESS OF SHIGA-LIKE TOXIN-PRODUCING ESCHERICHIA-COLI O101 STRAINS OF HUMAN AND PORCINE ORIGIN

Shiga-like toxin (SLT)-producing Escherichia coli (SLTEC) O101 has rec ently been associated with hemorrhagic colitis and hemolytic-uremic sy ndrome in humans. In this study, SLTEC O101 strains from humans and pi gs were characterized for clonal relatedness by nucleotide sequence an alysis of their slt genes, DNA fingerprinting of genomic DNA, and dete rmination of virulence factors. The slt genes of five E. coli O101 str ains were cloned and sequenced. For all strains, the deduced amino aci d sequences of the B subunits were identical to those of the SLT-Ile p resent in the classical SLTEC O139 strains that cause edema disease in pigs. The A subunit revealed more than 99% homology to that of SLT-Il e. DNA fingerprinting revealed a high degree of genetic relatedness be tween the human and porcine O101 isolates, None of the O101 strains in vestigated had virulence factors frequently found in porcine (F107 fim briae or heat-stable or heat-labile enterotoxins) or human SLTEC strai ns (eaeA or enterohemorrhagic E. coli hemolysin). The absence of virul ence factors typical of SLT-I- and SLT-II-producing E. coli together w ith the presence of SLT-Ile, a toxin previously seen only in porcine E . coli, suggests a new pathogenic mechanism for E. coli O101 infection of humans. For diagnostic purposes, we recommend the use of PCR prime rs and DNA probes complementary to slt-Ile to correctly identify such strains and to further evaluate their role in human diseases.