Diversity of the virulence genes of Gardnerella vaginalis isolates across the different bacterial vaginosis states in a South African pregnant cohort

Abstract

Background: Gardnerella vaginalis (G. vaginalis) has been recognised as the characteristic microorganism in bacterial vaginosis (BV), but its contribution to the pathogenesis of BV remains poorly understood and is largely understudied in South Africa. This study investigated the diversity of the virulence factors (i.e. vaginolysin [vly], sialidase [sld] and phospholipase C [pho]) of G. vaginalis in pregnant South African women across the BV positive, BV intermediate, and BV negative states to determine their relation to BV status.

Methods: This study included 150 pregnant women recruited from a public hospital in Durban, South Africa. Enrolled women provided two self-collected vaginal swabs for BV diagnosis by Nugent score and cultivation of G. vaginalis for further laboratory testing. Amplification, sequencing, and phylogenetic analysis were performed to detect the presence of vly, sld and pho genes of G. vaginalis.

Results: A total of 16 G. vaginalis isolates were successfully cultured from the study population. Of these 16 isolates, 14 (87.5%) were positive for vly, 15 (93.8%) were positive for sld, and 13 (81.3%) were positive for pho. There were 11 (68.8%) isolates that harboured all three virulence factors. Phylogenetic analysis revealed cluster heterogeneity for all three virulence factors, indicative of little to no diversity across the BV states.

Conclusion: This study was the first to report on the virulence factors of G. vaginalis isolates found in the different BV states from pregnant South African women. Understanding the pathogenic mechanisms of G. vaginalis is vital to combat BV infection and will aid in prevention and treatment strategies for BV.