Molecular genetic characteristics of Vibrio cholerae nonO1/nonO139 strains isolated on the territory of Russian Federation from patients with otitis

Abstract

Introduction. In 2017–2020 for the first time in many years strains of Vibrio cholerae nonO1/nonO139 (NAGs) were isolated in Russia from patients with otitis.Aim — bioinformatic analysis of whole genome sequences (WGSs) and sequences of individual genes of NAG strains - causative agents of otitis isolated in Russia.Materials and methods. Analysis of WGSs of eight NAG clinical isolates obtained on the MiSeq Illumina platform was carried out using BioEdit, BLASTN, BLASTP, Vector NTI programs; antibiotic resistance was determined according to MUK 4.2.2495-09.Results. The strains differed in SNP content, sets of determinants of pathogenicity/persistence factors and their alleles. All lacked CTX, preCTX, RS1 prophages, VPI pathogenicity island, thermostable toxin gene, mobile elements associated with antibiotic resistance, pandemicity island VSP-I; two strains contained VSP-II island. Genes of a number of proteases, cholix toxin, type 3 secretion system (T3SS) cluster and additional T6SS clusters formed different combinations. Products of the altered genes retained or lost their characteristic active domains. In the cytotoxin MARTX of 6 strains, the key ACD domain was absent; in 4 strains a new rtxA-like domain was revealed. Biofilm gene clusters varied in their structure. The presence of genes for antibiotic resistance did not always correlate with antibioticograms. All strains were susceptible to most antibiotics, but some showed resistance to 1–4 drugs.Conclusion. All the studied strains — causative agents of otitis, in spite of revealed differences, have sufficient sets of determinants responsible for realization of pathogenic and persistent potential. Due to discrepancy between the genotypic and phenotypic characteristics of antibiotic resistance, one should rely mainly on the phenotype when choosing drugs for the etiotropic therapy of NAG infections. Emergence of patients with otitis caused by NAG-vibrios in Russia indicates the advisability of the inclusion of tests for their identification in the scheme of bacteriological analysis for extraintestinal infections and, in cases of their isolation, for prompt determination of sensitivity to antibiotics.