[Differences in virulence genes in Vibrio cholerae eltor strains isolated from different sources in Turkmenistan...

Polymerase chain reaction (PCR) detected the presence of various genes associated with virulence in genome of strains V. cholerae eltor isolated in Turkmenistan territory during epidemic and epidemic-free perios. It was found that a complete set of virulence genes (ctxA+, tcpA+ and toxR+) contained strains isolated from patients, carriers and environment only in cholera epidemics. Strains isolated from the environment in the period free of epidemics did not contain ctxA and tcpA in 78.2% of cases, but 5.2% of the strains carried a complete set of virulence genes. There were also nontoxigenic strains containing genes tcpA and toxR. Such strains were isolated from the environment (16.6%) and vibrion carriers (42.9%). Isolated were also strains V.cholerae eltor carrying bacteriophage CTX phi with incomplete set of virulence genes and having genotype ctxA-, ace+ and zot+. Almost all the strains ctxA-, tcpA+ carry attRS1-site in genome. This shows that such strains may transform into toxigenic as a result of infection with bacteriophage CTX phi.