AUTHOR=Castro Joana , Rosca Aliona S. , Cools Piet , Vaneechoutte Mario , Cerca Nuno 

TITLE=Gardnerella vaginalis Enhances Atopobium vaginae Viability in an in vitro Model

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2020.00083

DOI=10.3389/fcimb.2020.00083

ISSN=2235-2988

ABSTRACT=<p>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 <italic>Gardnerella</italic>, which then becomes a scaffold for other species to adhere to. One of the species often found incorporated in <italic>Gardnerella</italic> mediated biofilms is <italic>Atopobium vaginae</italic>. Interestingly, <italic>A. vaginae</italic> is very rarely found without the presence of <italic>Gardnerella</italic>. However, not much is known regarding the interactions between <italic>A. vaginae</italic> and <italic>Gardnerella</italic> species. This study assessed biological interactions between <italic>Gardnerella vaginalis</italic> and <italic>A. vaginae</italic>. In our <italic>in vitro</italic> model, by using specific <italic>Gardnerella</italic> and <italic>A. vaginae</italic> Peptide Nucleic Acid (PNA)-Fluorescence <italic>In Situ</italic> Hybridization (FISH) probes, we confirmed that <italic>A. vaginae</italic> was able to incorporate a pre-formed <italic>G. vaginalis</italic> biofilm, accounting for up to 20% of the total number of biofilm cells. However, our findings showed that almost 92% of <italic>A. vaginae</italic> cells lost viability after 48 h of mono-species planktonic growth, but were able to maintain viability when co-cultured with <italic>Gardnerella</italic> or after pre-conditioning with cell-free supernatant of <italic>Gardnerella</italic> cultures. While the <italic>in vitro</italic> conditions are very different from the <italic>in vivo</italic> microenvironment, this study contributes to a better understanding of why <italic>A. vaginae</italic> vaginal colonization rarely occurs in the absence of <italic>Gardnerella</italic>. 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.</p>