Detection and characterization of verotoxigenic Escherichia coli by a VTEC/EHEC multiplex PCR in porcine faeces and pig carcass swabs.

To determine whether pigs and pig carcasses are a reservoir of verotoxigenic-producing Escherichia coli, a sensitive and rapid isolation method was developed. A VTEC/EHEC multiplex PCR method was developed to test all samples taken at the farm (n=289) and at the slaughterhouse (n=233). From the 137 positive VTEC/EHEC multiplex PCR farm samples, 54 strains were isolated that carried one virulence gene. Of these, thirty-one strains carried the vt2e variant of the vt2 gene, which causes oedemic disease in young pigs, four strains contained the hlyA gene and 19 the eaeA gene. All strains isolated were further identified with an enterotoxigenic E. coli (ETEC) multiplex PCR developed to detect the LTI, STIa, STII and vt2 genes in a single reaction. One-third of the vt2e-positive strains also contained the STIa gene. A small fraction of the 132 carcasses tested were found positive for VTEC or the E. coli O157 serotype. We conclude that none of the isolated strains carried a combination of virulence genes indicative of potential human pathogenic characteristics.