Further evaluation of the Biken test (modified Elek test) for detection of enterotoxigenic Escherichia coli producing heat-labile enterotoxin and application of the test to sampling of heat-stable enterotoxin.

A total of 2,229 strains of Escherichia coli isolated from subjects with traveller's diarrhea were tested for heat-labile enterotoxin production by the Biken test (Honda et al., J. Clin. Microbiol. 13:1--5, 1981). Results of the Biken test showed a 99.0% coincidence with those obtained by Chinese hamster ovary cell assay. The use of antiserum against E. coli heat-labile enterotoxin gave sharper and clearer results than did the use of antiserum against cholera enterotoxin. Samples for heat-stable enterotoxin assay were obtained from the agar plates used for the Biken test, and the heat-stable enterotoxin activities of these samples were compared with those of samples obtained from standard liquid cultures. Results for samples of 2,229 strains from the Biken agar plates and from liquid cultures were almost identical.