First report on the biotypes and genotypes of Gardnerella vaginalis isolates from Durban, South Africa

Abstract

Background: The diversity of Gardnerella vaginalis (G. vaginalis), the predominant pathogen responsible for the onset and progression of bacterial vaginosis (BV), is yet to be explored in the South African setting. Diversity assessments are needed to establish links between the genotypes and biotypes of G. vaginalis with BV status. This study investigated the phenotypic (biotypes) and genotypic (genotypes) diversity of G. vaginalis from South African pregnant women diagnosed as BV-positive, intermediate, and negative.

Methods: The study population included 150 pregnant women recruited from a public hospital in Durban, South Africa, who provided two self-collected vaginal swabs for BV diagnosis by Nugent scoring and G. vaginalis culture. Biotypes were assigned based on ?-galactosidase, lipase, and hippurate test profiles. Genotypes were generated with amplified ribosomal deoxyribonucleic acid restriction analysis (ARDRA) of the 16S ribosomal ribonucleic acid (rRNA) gene, and restriction fragments were obtained with TaqI digestion. Phylogenetic analysis was performed on the sequenced 16S rRNA amplicons.

Results: In this study, 49.3% of the women were BV-negative, 28.7% were intermediate, and 22% were positive. A significant association (p = 0.025) existed between reported symptoms of abnormal vaginal discharge and BV status. There were 16 G. vaginalis isolates cultured from the study population, within which four different genotypes were detected, with genotype 1 (GT1) being dominant. The most prevalent biotype was biotype 3. The most frequent genotype/biotype pairing across the isolates was GT1/biotype 3, distributed across the BV-negative and intermediate groups. Phylogenetic analysis revealed heterogeneity in the gene clusters and certain biotypes, i.e. G. vaginalis isolates from BV-intermediate and positive women clustered together and shared similar biotypes.

Conclusion: This study was the first to report on the genotypic and phenotypic diversity of G. vaginalis isolates from South African pregnant women. Diversity assessments of G. vaginalis may elucidate the pathogenic potential of this microorganism.