ABSTRACT
AIM: Comparative molecular-genetic analysis of clinical Vibrio cholerae eltor biovariant strains isolated in Russia during various years. MATERIALS AND METHODS: Microbiological and biochemical methods were used for studies of 25 clinical strains of classic and eltor biovariant cholera, PCR testing and sequencing of various genes was also performed. RESULTS: Phenotypic and genetic analysis of clinical V. cholerae strains isolated in Russia during 7th cholera pandemic has confirmed that they belong to biovariant eltor. PCR testing of 21 isolates obtained from patients in 1970 - 2010 has shown that epidemic complications in Russia from 1993 were caused by altered V. cholerae biovariant eltor. Presence of classic cholera biovariant ctxB coding gene in cholera toxin coding CTX prophage is the genetic alteration of these variants, ctxB sequencing in altered variants has confirmed PCR data and shown 2 ctxB gene alleles (ctxB1 and ctxB7). Altered variants produced significantly more cholera toxin than typical strains. CONCLUSION: In 1970 - 2010 67.6% of clinical isolates were altered V. cholera biovariant eltor variants. These new variants were genetically diverse. Alteration of cholera eltor biovariant genome caused toxigenicity increase.
