Abstract
Bacterial vaginosis (BV) is a common vaginal condition in women of reproductive age. During BV development, BV-associated bacteria may form a polymicrobial biofilm, which predispose women to recurrent BV. The aim of the study was to investigate the growth forms of Gardnerella spp. and Lactobacillus spp. and to determine the association between the bacterial growth forms and clinical characteristics [urinary tract infection (UTI) symptoms, human immunodeficiency virus (HIV) infection and abnormal vaginal discharge] in women attending a tertiary hospital in Pretoria, South Africa. A first-void urine specimen was collected from 196 women and BV was diagnosed using the Nugent scoring and the Ison-Hay criteria (vaginal smear microscopy). Fluorescence in situ hybridisation (FISH) was performed to classify the growth forms [“dispersed” or “biofilm”]. Bacterial cells were categorized as “dispersed” if cells were scattered separately and as “biofilm” if bacterial aggregates on the vaginal epithelial cells were observed. BV was detected in 52 women (52/196; 27%) and in these women, Gardnerella spp. were predominantly present in biofilms (46/52; 88% for Nugent scoring; and 45/50; 90% for Ison-Hay criteria), whereas Lactobacillus spp. were predominantly present in a dispersed form (38/52; 73% for Nugent scoring; and 37/50; 74% for Ison-Hay criteria). The odds of having BV increased when Gardnerella biofilms were present (p < 0.001), whereas the opposite was observed for Lactobacillus biofilms (p = 0.001). Neither Gardnerella spp. or Lactobacillus spp. (both dispersed or biofilms) had an association with the presence of UTI symptoms, HIV coinfection or abnormal vaginal discharge. In conclusion, this study demonstrated and confirmed that Gardnerella biofilms are associated with BV and that Lactobacillus spp. may form biofilms to protect against BV.
Highlights
Bacterial vaginosis (BV) is the most common vaginal disease in women of reproductive age (Kenyon et al, 2013)
The Ato291 probe had a positive signal for A. vaginae ATCC R BAA-55TM; the Ato291 probe cross-hybridized with L. crispatus ATCC R 33820TM
The findings in this study demonstrate that Gardnerella spp. are predominantly present in biofilms on vaginal cells of BV-positive women, while Lactobacillus spp. are present in a dispersed growth form
Summary
Bacterial vaginosis (BV) is the most common vaginal disease in women of reproductive age (Kenyon et al, 2013). Gardnerella spp. have long been suggested as an etiological agent of BV since its discovery (described as Haemophilus vaginalis) by Gardner and Dukes (1955), but its role in BV etiology has remained controversial over the years because of its presence in the microbiota of “healthy” women (Zhou et al, 2004; Ravel et al, 2011; Shipitsyna et al, 2013). This controversy could partially be explained by the evidence that four different genotypes/clades (or 13 genomic species) may exist within the genus Gardnerella (Santiago et al, 2011; Ahmed et al, 2012; Vaneechoutte et al, 2019), and that there are differences in virulence potential between avirulent and virulent strains of Gardnerella spp. This controversy could partially be explained by the evidence that four different genotypes/clades (or 13 genomic species) may exist within the genus Gardnerella (Santiago et al, 2011; Ahmed et al, 2012; Vaneechoutte et al, 2019), and that there are differences in virulence potential between avirulent and virulent strains of Gardnerella spp. (Harwich et al, 2010; Janulaitiene et al, 2018)
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