Bacterial vaginosis (BV) is a polymicrobial phenomenon that represents dybiosis or imbalance in the vaginal microflora. Gerald Murray today presented the findings of a cohort study that examined the relationship between the vaginal microbiome and BV.

298 women without BV underwent periodic assessment of their vaginal microbiota by 16s rRNA sequencing. Over two years of follow-up 51 women developed BV, giving an incidence of 9.75/100 woman-years. 

Certain taxa were associated with subsequent development of BV - a 1% increase in Gardnerella vagainalis conferred a 2% increase in BV. The poorly characterised, non-cultivable BBAV TM7 was associated with a 5-fold increase in BV, but Atopobium vaginae was not. 

Diversity of the vaginal flora was correlated with susceptibility to BV. Women with more diverse microbiome experienced greater fluctuations in flora between assessments, and these unstable microbiomes were more likely to develop BV. Interestingly, the acquisition of microbial changes associated with an increased BV susceptibility often preceded the development of clinically apparent BV by weeks or even months. 

Behavioural factors were also associated with the development of BV: a higher rate pf partner change and the acquisition of a new partner were associated with incident BV. This is consistent with the emerging view of BV as a sexually transmissible phenomenon. 

Then authors  hypothesise that BV is a sexually acquired instability in the vaginal microbiome that ultimately leads to a lack of resilience in a complex community.