Characterization of Vibrio cholerae O139 belonging to multiple ribotypes and isolated from diarrhoeal patients in Kerala, southern India

摘要

Twenty-four Vibrio cholerae O139 strains isolated from Kerala, southern India were characterized by PCR, CTX typing and ribotyping; all of which, except three strains, carried the core of the CTX genetic element, colonization-toxin co-regulated pilus, the adherence outer membrane protein, haemolysin, central regulatory protein encoded toxR, SXT genetic element, and produced cholera toxin and biofilm. Results of RFLP analysis revealed twenty-one of the 0139 strains possess two copies of CTX Phi and pre-CTX Phi always preceded by tandemly arranged RS1 element: one had two copies of pre-CTX Phi and two a single copy of pre-CTX Phi. Nucleotide sequencing detected classical ctxB in CTXET Phi and CTXCalc Phi with additional change at 28th amino acid position of CTXCalc Phi. Ribotype analysis revealed the presence of multiple ribotypes, including B-I and B-II, and new ribotypes designated B-VIIIa, B-VIIIb and B-IX, not reported earlier among V. cholerae O139 strains. These observations thus indicate that genetic recombination or mutations had occurred in conserved rrn operon and variations in CTX Phi may have implications on the evolution of the organism