Assessment of the Variation Range of Agglutinability in <i>Vibrio cholerae</i> Strains Isolated in the Course of Monitoring Studies

Abstract

The aim of the study was to retrospectively analyze the range of variability of antigenic properties and genotypic characteristics of Vibrio cholerae R-variant strains atypical in terms of agglutinability.Materials and methods. 169 strains of V. cholerae R-variant with atypical agglutinability have been studied using the “AmpliSens® Vibrio cholerae-FL” test-system. The determination of O1 antigen was carried out using the “Ig-V. cholerae О1/О139 – ELISA/dot-ELISA” reagent kit.Results and discussion. A retrospective analysis of the complex of phenoand genotypic characteristics of strains isolated from surface water bodies in the territories of three former Soviet republics and 13 constituent entities of the Russian Federation in the course of 30-year monitoring and identified upon isolation as nontoxigenic V. cholerae R-variant strains has been performed. Upon re-identification, it was found that the strains belong to both epidemically dangerous (3.0 %) and non-dangerous strains (97.0 %). The range of variability was expressed in their distribution into three groups and consisted in retaining of agglutinability only with cholera RO serum in the first group (34.5 % of strains); the loss of this trait, but the acquisition of the ability to agglutinate in different combinations with O1, Ogawa or Inaba sera – in the second (16.7 %); and also in the loss of agglutinability with all diagnostic cholera sera – in the third (48.8 %). The presence of the wbeT gene in the compared V. cholerae classical R-variant strain does not exclude the presence of the genomic region for O1 antigen biosynthesis in other R-strains, possibly in a modified form, which can be clarified in further molecular-genetic studies. Alternatively, such strains are likely to be attributed to V. cholerae nonO1/nonO139. Strains of V. cholerae R-variant with different amounts of surface antigen (optical density range – from 0.088±0.002 to 1.226±0.003) have been identified. The data obtained can be used for monitoring of cholera in laboratories of regional and federal levels.

Keywords

• <i>vibrio cholerae</i>
• r-variant
• variability
• agglutinability
• phenotype and genotype
• monitoring
• environmental objects