A competitive enzyme-linked immunosorbent assay for detecting Escherichia coli heat-stable enterotoxin and its application to clinical isolates.

Enterotoxigenic Escherichia coli (ETEC) are well recognised enteric pathogens. The epidemiology of heat-stable enterotoxin (STa) producing strains has not been established due mainly to difficulties encountered in performing bioassays on a large scale in baby mice. This study describes a competitive enzyme-linked immunosorbent assay (ELISA) for detecting STa and its application to clinical isolates. Compared to the bioassay, the ELISA had a specificity of 93.7% and a sensitivity of 90.9%. It detected as little as 1 microgram/l STa. Of 720 E. coli isolates from children with diarrhoea, 69 (9.6%) were positive for STa by ELISA.