MLVA-typing of Vibrio choleraе El Tor Strains Isolated in Transbaikal Territory during the Seventh Pandemic

Abstract

Cholera remains a topical infection in the world, which determines the high risk of importation of the pathogen on the territory of the Russian Federation. MLVA-typing of 135 strains at 5 tandem repeats loci was carried outin order to study the clonal-population structure of the isolated from 1973 to 2016 on the Transbaikal territory V. cholerae. Analysis of the distribution patterns showed that the primary emergence of strains with new atypical for the territory genotypes in 1970s, 1980s, 1990s, occurred in sewage waters with the subsequent detection of the given genotypes generally in Ingoda river and Kenon lake. The strains firstly isolated from Borzya river and Haranor lake and found out at various times in Ingoda river and Kenon lake, Chita, Argun rivers, Haranor lake and Borzya river have been dominating since 2005 in Transbaikal territory. Finding groups of isolates with identical or similar MLVA-profile appeared in cluster complexes evidence of their long-term preservation in specific ecological niches, strains’ allelic profiles undergo minor transformation on the most variable loci in the process of adaptation. Identification of V. cholerae El Tor that variable tandem repeat loci structure materially differs from those of the dominant clones may serve as proof of their invasive origin.