Detection of Escherichia coli serogroups O26, O103, O111 and O145 from bovine faeces using immunomagnetic separation and PCR/DNA probe techniques.

AIMS: The aim of this study was to isolate Escherichia coli O26, O103, O111 and O145 from 745 samples of bovine faeces using (i) immunomagnetic separation (IMS) beads coated with antibodies to lipopolysaccharide, and slide agglutination (SA) tests and (ii) PCR and DNA probes for the detection of the Verocytotoxin (VT) genes. METHODS AND RESULTS: IMS-SA tests detected 132 isolates of presumptive E. coli O26, 112 (85%) were confirmed as serogroup O26 and 102 had the VT genes. One hundred and twenty-two strains of presumptive E. coli O103 were isolated by IMS-SA, 45 (37%) were confirmed as serogroup O103 but only one of these strains was identified as Verocytotoxin-producing E. coli (VTEC). Using the PCR/DNA probe method, 40 strains of VTEC O26 and three strains of VTEC O103 were isolated. IMS-SA identified 21 strains of presumptive E. coli O145, of which only four (19%) were confirmed as serogroup O145. VTEC of this serogroup was not detected by either IMS-SA or PCR/DNA probes. E. coli O111 was not isolated by either method. CONCLUSION: IMS beads were 2.5 times more sensitive than PCR/DNA probe methods for the detection of VTEC O26 in bovine faeces. SIGNIFICANCE AND IMPACT OF THE STUDY: IMS-SA is a sensitive method for detecting specific E. coli serogroups. However, the specificity of this method would be enhanced by the introduction of selective media and the use of tube agglutination tests for confirmation of the preliminary SA results.