The detection of verocytotoxins in bacterial cultures from human diarrhoeal samples with monoclonal antibody-based ELISAs.

Bacterial cultures from 1801 human diarrhoeal faecal specimens were examined for verocytotoxins I and II by monoclonal antibody-based sandwich ELISAs. Of the 68 ELISA-positive cultures selected from initial screening, 32 were positive by ELISA on repeat or from freshly grown cultures. ELISA-positive pure cultures were obtained from 13 of these, of which seven were confirmed as verocytotoxin positive by cytotoxicity assay. These seven strains were typed as O26 (5) and O146 (2). The six false positive results were from isolates of Enterobacter sp. (1), Citrobacter Freundii (1) and Escherichia coli (4), one each of types O1, O18ac and O98 and an untypable strain. Despite the occurrence of false positive reactions, sandwich ELISA was a useful method for the rapid screening of samples, and detected verocytotoxin-positive E. coli strains, other than O157, from patients with clinical conditions in which they could be implicated.