Phenotypic variation of Gardnerella vaginalis subgroups in relation to virulence potential

Abstract

Background Phenotypic and genotypic diversity of vaginal bacteria Gardnerella vaginalis resulted in its classification into genotypic subgroups. The virulence potential of these subgroups was evaluated. Methods G. vaginalis clinical isolates were subtyped on the basis of subgroup-specific genes by PCR. The virulence-related phenotypic characteristics of the isolates were evaluated assessing their in vitro ability to grow as biofilm on abiotic surfaces, produce the toxin vaginolysin, and express sialidase activity. Vaginolysin in the supernatant of the cultures was quantified using toxin-specific antibodies by sandwich ELISA. Sialidase activity was tested using fluorogenic substrate. Cloning and expression of the sialidase gene of G. vaginalis in E. coli was performed. Differences in the expression of phenotypic properties of the isolates were evaluated by agglomerative hierarchical clustering and principal component analysis. Results Thirty-five clinical isolates of G. vaginalis were subtyped into three subgroups 1, 2 and 4. Analysis of sialidase activity indicated statistically significant differences among the subgroups. All isolates were grouped into three clusters by the methods of statistical analysis. The distinct profile of each cluster was based on the phenotypic characteristics of isolates. Subgroup 4 was the most homogenous group, as all isolates were found in the same cluster, which was characterized by the low production of all studied virulence factors. Subgroup 2 isolates were mainly distributed between two clusters, whereas subgroup 1 isolates were found in all three clusters. Conclusion G. vaginalis subgroups with different virulence potential might play distinct roles in vaginal microbiota.