Association of genes encoding P fimbriae, CS31A antigen and EAST 1 toxin among CNF1-producing Escherichia coli strains from cattle with septicemia and diarrhea.

Fifty-six CNF1-producing Escherichia coli strains isolated from cattle with diarrhea or septicemia were screened by PCR for the detection of pap, sfa, afa, clpG, or f17 adherence factor and EAST 1 toxin genes. All the isolates were pap-positive, in accordance with the close association of pap, CNF1 and alpha-hemolysin genes observed on human and porcine E. coli. Only the gene encoding the P adhesin of class III (PrsG) was detected. Genes encoding CS31A antigen (71%) and S fimbriae (34%) (but not Afa or F17) were detected among the bovine isolates. E. coli producing both CNF1 and plasmid-encoded CS31A is a new example of association between bacterial clones and plasmid-mediated virulence factors. The EAST 1 toxin-encoding gene was detected on 66% of the CNF1-producing isolates but was linked to CS31A rather than to CNF1. These results suggest a close association between EAST 1 toxin and the adherence factor CS31A among pathogenic bovine E. coli.