Gardnerella vaginalis Enhances Atopobium vaginae Viability in an in vitro Model

Abstract

Bacterial vaginosis (BV) is the most common vaginal infection among women of reproductive age. A hallmark of BV is the presence of a highly structured polymicrobial biofilm on the vaginal epithelium, presumably initiated by facultative anaerobes of the genus Gardnerella, which then becomes a scaffold for other species to adhere to. One of the species often found incorporated in Gardnerella mediated biofilms is Atopobium vaginae. Interestingly, A. vaginae is very rarely found without the presence of Gardnerella. However, not much is known regarding the interactions between A. vaginae and Gardnerella species. This study assessed biological interactions between Gardnerella vaginalis and A. vaginae. In our in vitro model, by using specific Gardnerella and A. vaginae Peptide Nucleic Acid (PNA)-Fluorescence In Situ Hybridization (FISH) probes, we confirmed that A. vaginae was able to incorporate a pre-formed G. vaginalis biofilm, accounting for up to 20% of the total number of biofilm cells. However, our findings showed that almost 92% of A. vaginae cells lost viability after 48 h of mono-species planktonic growth, but were able to maintain viability when co-cultured with Gardnerella or after pre-conditioning with cell-free supernatant of Gardnerella cultures. While the in vitro conditions are very different from the in vivo microenvironment, this study contributes to a better understanding of why A. vaginae vaginal colonization rarely occurs in the absence of Gardnerella. Overall, this highlights the importance of microbial interactions between BV-associated bacteria and demands more studies focused on the polymicrobial bacterial communities found in BV.

Evaluation of different culture media to support in vitro growth and biofilm formation of bacterial vaginosis-associated anaerobes

“…It is of note that Gardnerella sp. UM241 did not match with any of the Gardnerella species described by Vaneechoutte and colleagues ( Vaneechoutte et al, 2019 ) (i.e., G. vaginalis , G. piotii , G. leopoldii and G. swidsinskii ), belonging to a yet unidentified Gardnerella species ( Castro et al, 2020 ).…”

“…UM: University of Minho, Portugal. In addition, the strain was phenotypically and genotypically characterized by Castro et al (2020 , 2015 ), Castro, Jefferson & Cerca (2018) . It is of note that Gardnerella sp.…”

“…biofilms is Atopobium vaginae ( Swidsinski et al, 2005 ). Under specific in vitro conditions, G. vaginalis enhances culturability of A. vaginae ( Castro et al, 2020 ) and it has been suggested that the in vivo detection of both bacteria is a strong indicator of BV development ( Bradshaw et al, 2006 ; Hardy et al, 2016 , 2015 ; Muzny et al, 2019 ). However, the BV biofilm is often populated by many other facultative or strict anaerobes, but very little is known about their role in BV development.…”

Novel systems analysis elucidates the influence of personalized variation in microbiome composition on metronidazole efficacy in bacterial vaginosis

“…vaginalis at steady state. 72 Sensitivity to MNZ (EC50 and kkill): MNZ is highly variable, and typically obligate anaerobes are considered the most sensitive to MNZ. The strain of G. vaginalis used in the basis of this model is relatively resistant to MNZ, with growth barely inhibited at 256 g/ml (9% inhibition compared to 0 g/ml control, Fig.…”

“…51 Additionally, G. vaginalis is associated with promoting the growth of other BV-associated bacteria like A. vaginae. 72 Calculations were completed assuming the reported mono and co-cultures were at steady state to derive equation 3 and 4. Equations 2 and 3 relate to the parameter table S3 in equations 5 and 6, which generalizes the reported interaction strength from the literature to be able to be adjusted for varying carrying capacities simulated in the model that do not equal the carrying capacities from the literature.…”