PHENOTYPIC AND GENOTYPIC CHANGES IN VIBRIO-CHOLERAE O139 BENGAL

To find reasons for the recent decline of Vibrio cholerae O139 Bengal cholera in Bangladesh, phenotypic and genotypic changes in O139 isolat es obtained from patients viith cholera from 1993 to 1996 were studied , The isolates mere tested for the presence of ctx and tcpA genes, hem agglutinin/protease (HA/P), capsule, D-mannose-sensitive hemagglutinin (MSHA), L-fucose-sensitive hemagglutinin (FSHA), tube test (tube) and CAMP test (CAMP) hemolytic activities, resistance to 2,4-diamino-6,7- diisopropyl pteridine (O1/29) and trimethoprim-sulfamethoxazole (TMP-S MX), and genotype by pulsed-held gel electrophoresis (PFGE), All isola tes possessed ctx and tcpA genes, HA/P, and a capsule, Most isolates w ere negative for FSHA, but although the majority of the isolates mere positive for MSHA, no discernible trend in the activity was found duri ng the study period, All early isolates mere CAMP hemolysin positive a nd resistant to the vibriostatic compound O/129 and TMP-SMX, the two p roperties that could be used for the presumptive diagnosis of O139 cho lera, However, subsequently, isolates that mere CAMP hemolysin negativ e and susceptible to TMP-SMX and O/129 were increasingly encountered, with ail the 1996 isolates being so, which suggested that these proper ties can no longer be used for the presumptive diagnosis of O139 chole ra, V. cholerae O139 isolates that were CAMP hemolysin positive and re sistant to O/129 and TMP-SMX produced a disease of greater severity th an that caused bg the CAMP hemolysin-negative and susceptible isolates on the basis of the lengths of stay of the hospitalized patients, The study period witnessed the evolution of four different genotypes by P FGE, All of these data suggested that the V. cholerae O139 isolates ha ve undergone changes in same properties. However, how these changes in fluenced their prevalence relative to that of V. cholerac O1 in human infection is not clear, Studies of the environmental factors mill prov ide the key for an understanding of the relative abundance of these vi brios.