Abstract
Bacterial vaginosis (BV), characterized by a shift of the vaginal microbiota from a Lactobacillus-dominated community to a dense biofilm containing a complex mixture of organisms, is an important risk factor in poor reproductive health outcomes. The Nugent score, based on Gram stain, is used to diagnose BV and Gardnerella vaginalis abundance in the sample is one factor determining Nugent score. A high Nugent score is indicative of BV but does not always correspond to the presence of clinical symptoms. G. vaginalis is recognized as a heterogeneous group of organisms, which can also be part of the normal, healthy vaginal microbiome. In addition, asymptomatic BV and non-Gardnerella types of BV are being recognized. In an attempt to resolve the heterogeneous group of G. vaginalis, a phylogenetic tree of cpn60 universal target sequences from G. vaginalis isolates was constructed that indicates the existence of four subgroups of G. vaginalis. This subdivision, supported by whole genome similarity calculation of representative strains using JSpecies, demonstrates that these subgroups may represent different species. The cpn60 subgroupings did not correspond with the Piot biotyping scheme, but did show consistency with ARDRA genotyping and sialidase gene presence. Isolates from all four subgroups produced biofilm in vitro. We also investigated the distribution of G. vaginalis subgroups in vaginal samples from Kenyan women with Nugent scores consistent with BV, Intermediate and Normal microbiota (n = 44). All subgroups of G. vaginalis were detected in these women, with a significant difference (z = −3.372, n = 39, p = 0.001) in frequency of G. vaginalis subgroup B between BV and Normal groups. Establishment of a quantifiable relationship between G. vaginalis subgroup distribution and clinical status could have significant diagnostic implications.
Highlights
Gardnerella vaginalis, first isolated by Leopold in 1953 [1], has long been recognized in vaginal samples and has been identified by several names, including Haemophilus vaginalis by Gardner and Dukes in 1955 [2]
Our results demonstrate that the cpn60 universal target sequence differentiates distinct subgroups within G. vaginalis and that only one of these subgroups (Subgroup B: Piot biotype 5, sialidase positive and amplified ribosomal DNA restriction analysis (ARDRA) genotype 1) was found to be significantly more abundant in women with bacterial vaginosis (BV) than women with normal vaginal microbiota in a retrospective analysis of metagenomic profiles of Kenyan women
To calculate the Nugent score, a Gram stained vaginal smear is assessed for the relative abundance of various bacterial morphotypes including Gram-positive large rods, Gram-negative/
Summary
Gardnerella vaginalis, first isolated by Leopold in 1953 [1], has long been recognized in vaginal samples and has been identified by several names, including Haemophilus vaginalis by Gardner and Dukes in 1955 [2]. The proposal to create the genus Gardnerella and allocation of Corynebacterium vaginale and Haemophilus vaginalis to this new taxon as Gardnerella vaginalis was put forward by Greenwood and Pickett [4], based on a taxonomic study that utilized DNA-DNA hybridization, biochemical analysis of the cell wall, and electron microscopy. G. vaginalis is strongly associated with bacterial vaginosis (BV), and is one of the most frequently isolated bacteria from women with symptoms of BV [5,6,7]. Abundance of G. vaginalis in vaginal samples has been associated with infertility and preterm labour [8]. Recent studies of vaginal microbiota indicate that G. vaginalis can be a part of the vaginal microbiota in clinically healthy women [6,12,13]
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