Association of genes encoding P fimbriae, CS31A antigen and EAST 1 toxin among CNF1‐producing Escherichia colistrains from cattle with septicemia and diarrhea

Fifty‐six CNF1‐producing Escherichia colistrains 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 α‐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. coliproducing 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.