[Comparative molecular-genetic analysis of mobile elements in natural strains of cholera agent].

The molecular-genetic peculiarities of the prophage CTXφ genome, the VPI-1 pathogenicity island, and the VSP-II pandemicity island in recently emerged, genetically altered Vibrio cholerae El Tor strains have been studied. The genome of the prophage CTXφ, which contains the ctxAB operon, which codes cholera toxin (CT), was shown to be unstable. A comparative analysis of the nucleotide sequences of the two phage genome regions (the ctxB gene and ctxAB operon promoter region) among 23 genovariant strains allowed us to reveal the presence of distinct ctxB gene alleles (ctxB1 or ctxB7) that differed in single-nucleotide substitutions and the polymorphism of the ctxAB operon promoter region. An analysis of the VPI-1 structure showed that tcpA gene that encodes the basic protein of the toxin-coregulated pilli (TCP) was represented in the genovariants by four alleles. The variability of the VSP-II was also revealed. It was manifested in the occurence of the deletions of varying length (2069 or 13 105 bp).