PREVALENCE OF VIBRIO-CHOLERAE WITH HEAT-STABLE ENTEROTOXIN (NAG-ST) AND CHOLERA-TOXIN GENES - RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISMS OF NAG-ST GENES AMONG VIBRIO-CHOLERAE O-SEROGROUPS FROM A MAJOR SHRIMP PRODUCTION AREA IN THAILAND

A total of 148 Vibrio cholerae isolates from a major shrimp production area in Southern Thailand were examined by colony hybridisation for g enes encoding heat-stable enterotoxin (NAG-ST) and cholera toxin (CT). Only non-O1 V. cholerae strains were found to harbour NAG-ST (14 of 1 46) whereas no strains hybridised with the CT probe. NAG-ST-positive V . cholerae non-O1 strains were isolated from shrimp farms situated clo se to urban areas. Five different O serogroups were found among NAG-ST positive non-O1 strains. Southern blot and restriction endonuclease a nalysis of NAG-ST-positive strains revealed a high degree of genetic d ivergence. A total of seven classes of enterotoxin gene patterns were found with HindIII and EcoRI restriction endonucleases. Enterotoxin ge ne patterns correlated with O-antigen expression in 84% of isolates te sted. In combination with other molecular techniques Southern blot ana lysis with an NAG-ST oligonucleotide probe could be useful for studyin g the molecular epidemiology of V. cholerae non-O1 strains.