Phenotypic Analysis and Genetic Characteristics of Clinical Strains of Vibrio paracholerae

Abstract

The aim of the study was to perform a comprehensive phenotypic and genetic study of clinical strains of Vibrio paracholerae isolated in the Russian Federation and neighboring countries. Materials and methods. We used 210 nucleotide sequences of complete genomes of V. cholerae nonO1/nonO139 and 12 strains of V. paracholerae that caused acute intestinal infections in 1975–2014. Motility, production of soluble hemagglutinin/protease, phospholipase, and hemolysin were determined using specialized media; antibiotic sensitivity - applying the disk diffusion method. BLAST, BioEdit (v.7.7.1), ABRicate, and the VFDB and CARD databases were used for bioinformatics analysis; fastANI v.1.34 – to calculate ANI. Results and discussion. The analysis of 210 V. cholerae nonO1/nonO139 genomes has revealed 12 genomes containing specific markers of V. paracholerae and lacking the loci characteristic of V. cholerae . Determination of the average nucleotide identity of the genomes confirmed their relationship to V. paracholerae . It has been established that paracholera vibrios, like cholera vibrios, are motile and produce pathogenic enzymes and hemolysin. All strains are sensitive to tetracycline, azithromycin, aminoglycosides, cephalosporins, and third-generation fluoroquinolones, but resistant to rifampicin (100 %), ampicillin (58.3 %), trimethoprime/sulfamethaxazole (25 %), and second-generation fluoroquinolones (16.7 %). Genomic analysis has revealed the absence of the CTXφ prophage and the VPI-1 pathogenicity island. A number of strains possesses isolated genes for the VSP-I and VSP-II pandemicity islands. Loci encoding additional pathogenicity determinants have been identified: hemolysin HlyA, soluble hemagglutinin protease HapA, MARTX toxin, type VI secretion system proteins, and cholyx toxin ChxA (in 75 % of isolates). All strains have RND-type efflux system loci, and 85.7 % of ampicillin-resistant isolates harbored carb β-lactamase genes. Thus, in terms of phenotypic characteristics and genetic structure, clinical isolates of V. paracholerae are similar to aquatic vibrios; pathogenicity factors specific to this group could not be identified. Despite the presence of multidrug-resistant isolates, sensitivity to most antibiotics used in the treatment of intestinal infections was noted.