Characterisation of the Vaginal Microbiota Using Culturomics and Metagenomics Suggests Transplantation of Gut Microbiota Into the Vagina During Bacterial Vaginosis

Abstract Background: Bacterial vaginosis is a very common vaginal disorder, with a gynaeco-obstetrical impact, but remains poorly understood. Current antibiotic treatment most often fails. Our objective was to exhaustively map the bacterial community present in bacterial vaginosis and normal flora, using not only a molecular approach but also a highly efficient culture approach, culturomics. Vaginal bacterial diversity was evaluated using both strategies for 24 Caucasian French women, including 7 cases of bacterial vaginosis, and 10 rural Senegalese women, including 5 cases of bacterial vaginosis. An additional 16 specimens (three cases of bacterial vaginosis and 13 normal flora) obtained during the follow-up visits of five French women with bacterial vaginosis were analysed using metagenomics.Results: The combination of culturomics and metagenomics reveals the richness and diversity of vaginal microbiota. Our data demonstrated that compared to healthy women, those with bacterial vaginosis present a shift in vaginal flora. The microbiota of the bacterial vaginosis group can be easily distinguished from that of healthy group by their increased bacterial diversity, abundance of Bacteroidales and Leptotrichiaeceae, and depletion of Proteobacteria and Lactobacillaceae species. In addition, a complex of 10 genera was associated with bacterial vaginosis: Gardnerella, Atopobium, Snethia, Aerococcus, Prevotella, Gemella, Facklamia, Porphyromonas, Mycoplasma, and Urinacoccus. Overall, the microbial population detected in bacterial vaginosis flora was largely similar to the bacterial communities found in gut microbiota. The two approaches showed a diverse vaginal microbiota that was largely non-overlapping, with only 146 common species. Furthermore, culturomics extends the repertoire of human-associated bacteria with the isolation of 27 new bacterial species.Conclusions: This study provides the most representative topology of the vaginal microbiota of normal flora and bacterial vaginosis and suggests the transplantation of gut microbiota into the vagina during bacterial vaginosis. Several sets of clinically relevant anaerobic bacteria and new species were also isolated from the human vagina, confirming that some previously “uncultivated” species may be cultivated using an appropriate strategy. Exhaustive characterisation of vaginal microbiota will enable a better understanding and management of bacterial vaginosis. Obtaining isolates will allow us to explore the bacterial interactions of the vaginal microbiota and will serve as a basis for the potential development of bacteriotherapy to prevent or treat vaginal dysbiosis.