[Differentiation of cholera-enterotoxin producing Vibrio strains by polymerase chain reaction]

The pathogenic factor of Vibrio cholerae that induces a severe watery diarrhea in humans is cholera enterotoxin (CT). We have earlier reported on the use of a specific polymerase chain reaction method (PCR) for confirmation of CT-production. In our results, a few CT-producing V. mimicus strains were detected by the method. Here we report on the PCR method using 2-primer sets in the same tube for differentiation of toxigenic V. cholerae (O1 and non-O1) and toxigenic V. mimicus. One primer pair is for CT-gene (ctx), and the other pair is for the toxR gene which regulates the ctx gene of V. cholerae. ToxR genes were detected in all CT-producing V. cholerae (both O1 and non-O1). There were no isolates of the ctx gene positive and toxR gene negative in all V. cholerae strains. On the other hand, V. mimicus strain has not recognized toxR genes except one strain which is similar to the character of V. cholerae. These results indicates that the CT-producing V. cholerae strains are regulated by the toxR gene, but the ctx gene of V. mimicus is controlled by another different genome from toxR of V. cholerae.