MOLECULAR ANALYSIS OF RIBOSOMAL-RNA AND CHOLERA-TOXIN GENES CARRIED BY THE NEW EPIDEMIC STRAIN OF TOXIGENIC VIBRIO-CHOLERAE-O139 SYNONYM BENGAL

Vibrio cholerae 0139 synonym Bengal recently caused large epidemics of cholera-like disease in Bangladesh and India. We compared the restriction fragment length polymorphisms of ctxA and rRNA genes (ribotypes) in 27 isolates of V. cholerae 0139 from patients in Bangladesh and India with those of 48 isolates of V. cholerae 01 from patients and 21 V. cholerae isolates from surface waters in Bangladesh, which included 2 0139 and 19 other non-01 isolates. Ribotyping of the isolates with BglI revealed that all 29 isolates of 0139 vibrios belonged to a single ribotype, suggesting a clonal nature of the infection. However, the 0139 vibrios comprised two ctxA genotypes and carried three or more copies of the ctxA gene, and the chromosomal locations of these copies were unlike those of the El Tor or classical vibrios. Analysis of the restriction fragment length polymorphisms of the rRNA genes suggested that V. cholerae 0139 isolates are more closely related to El Tor strains of V. cholerae 01 than were 19 other non-01 vibrios and 33 classical V. cholerae 01 isolates that were studied. However, further studies are needed to determine whether V. cholerae 0139 originated from mutations and genetic changes in a V. cholerae 01 strain or was due to the acquisition of virulence genes by a previously unknown V. cholerae non-01 strain.