Rapid visual detection of Escherichia coli and Vibrio cholerae Heat-labile enterotoxins by nitrocellulose enzyme-linked immunosorbent assay

Abstract

A modification of the enzyme-linked immunosorbent assay [ELISA] for a sensitive and rapid visual detection of heat-labile enterotoxins from E. coli and V. cholerae is described. Small amounts of bacterial supernatant fluids were bound to nitrocellulose filters which were used as sorbents in the nitrocellulose ELISA. The test was based on the immunological similarity between V. cholerae and E. coli heat-labile enterotoxins. Six isolates of V. cholerae and 48 isolates of E. coli were examined for heat-labile enterotoxins by the nitrocellulose ELISA and the Vero [African green monkey kidney] cell bioassay. With some strains, the nitrocellulose ELISA was more sensitive for detection of E. coli heat-labile enterotoxin than the Vero cell test. A similar result was obtained by endpoint titration of heat-labile enterotoxin-positive E. coli H10407 culture fluid in both assays. The sensitivity of the nitrocellulose ELISA for the detection of purified cholera toxin was at a level of 1 ng, a good result when compared with other serological assays.