Membrane filter assay for detection of enterotoxigenic Escherichia coli in epidemiological studies.

A membrane filter assay is described for detection of heat-labile toxin (LT) production by Escherichia coli. Bacterial colonies were isolated on a membrane filter which was then incubated on an agar medium containing anti-cholera toxin. LT produced by bacterial colonies diffused through the membrane filter, complexed with the antiserum, and formed a zone of precipitation in the agar. Requirements for reagents and materials were simple. The membrane filter assay showed good agreement with both the ganglioside-enzyme-linked immunosorbent assay and the DNA-DNA hybridisation assay and may prove to be an important technique for the study of the epidemiology of enterotoxigenic E coli in developing countries.