Comparative analysis of the structure of regulatory genes of Vibrio cholerae serotype О1 biotype El Tor strains

Abstract

Introduction. The expression of the ctxAB and tcpA-F genes encoding the main pathogenicity factors of the Vibrio cholerae is controlled by regulatory genes. The structure of these genes has not been fully studied in the pathogen strains isolated during different periods of the current pandemic. The aim of the study was a comparative analysis of the structure of regulatory genes of V. cholerae O1 biovar El Tor strains isolated on the territory of the Russian Federation and neighboring countries during the seventh cholera pandemic. Materials and methods. The nucleotide sequences of the complete genomes of 29 toxigenic strains isolated from 1970 to 2023 were analyzed. The analysis was carried out using BioEdit v7.2.6.1 software and Blast tool. Results. The analysis of ten regulatory genes (toxT, aphA, aphB, hns, hapR, vieA, luxO, luxT, carS, carR) was carried out. Almost all strains were found to have a thymine insertion in the hapR gene at position 219. The exception was V. cholerae strain M3208 (Tambov, 2023), which had an insertion of five nucleotides in this gene. Mutations of the luxO gene with an unknown effect were detected in 44.8% of the studied strains. In 46.7% and 33.3% of the studied genetic variants carrying the ctxB1 allele, non-synonymous substitutions were detected in the hns (G319A) and vieA (C235T) genes, respectively. All genetic variants with the ctxB7 allele have mutations in both the hns and vieA genes. Three genetic variants with the ctxB7 allele, imported to the Russian Federation in recent years, contain an altered structure of the carR gene (G265A). Conclusion. The structure of genes (toxT, aphA, aphB, carS, luxT, hapR) of V. cholerae O1 El Tor strains remains unchanged for the majority of the studied isolates. At the same time, variability in the hns (G319A), vieA (C235T) and carR (G256A) genes was detected. Mutations in these genes can be used as genetic markers of modern V. cholerae O1 El Tor genetic variants.