A comparison of a monoclonal antibody-based sandwich ELISA and immunomagnetic bead selective enrichment for the detection of Escherichia coli O157 from bovine faeces

Aims: To compare a recently developed monoclonal antibody (MAb) based sandw ich ELISA (sELISA) with an immunomagnetic separation (IMS) method for the d etection of Escherichia coli O157 in bovine faeces. Methods and Results: Faecal samples from 345 cattle were obtained from eigh t farms in Northern Ireland, in which human disease due to E. coli O157 had occurred. Both assays detected E. coli O157 on five of the farms and the p hage-type of the majority of the bovine strains were the same as the corres ponding human isolates. Similar numbers of the organism were detected by th e two methods, 59 by the sELISA and 53 by the IMS procedure, 39 of the posi tive samples being common to both. Twenty samples were sELISA positive/IMS negative. Conclusions: If the IMS is regarded as the gold standard, then the sELISA i s less sensitive and less specific, but under the conditions used sELISA po sitive results were obtained from all positive farms, and the sELISA gave a presumptive positive a day earlier than the IMS method. Significance and Impact of the Study: The sELISA has the potential to be us ed as a rapid method for screening large numbers of samples for E. coli O15 7, but further work is required to determine its specificity.