RAPID SCREENING METHOD FOR IDENTIFICATION OF CHOLERA TOXIN-PRODUCING VIBRIO-CHOLERAE O1 AND O139

A novel method of identifying cholera enterotoxin (CT)-producing Vibri o cholerae serogroups O1 and O139 was developed. The method uses degra dation of NAD as a specific biochemical marker for the CT-producing st rains. The substrate NAD at a concentration of 100 mu mol/liter was ma rkedly degraded when it was incubated at 37 degrees C for 2 h with the CT-producing strains at a final cell density equivalent to that of a twofold dilution of a McFarland no. 1 standard. NAD degradation was mo nitored by an enzyme-amplified color development assay. Subsequent tes ts conducted with a total of 119 strains of V. cholerae, including bot h clinical and environmental isolates, confirmed a significant correla tion between NAD degradation and CT production for all V. cholerae str ains belonging to serogroups O1 and O139. Since 2 of 11 non-Ol, non-O1 39 V. cholerae strains not carrying the CT gene degraded NAD, serotypi ng of the strains prior to the test is recommended.