It is true that some bacteria can be shared orally, and survive for certain periods of time in the mouth . This means that in theory, anyone who performs oral sex on a woman with bacterial vaginosis could get the infection in their mouth, and possibly even pass that infection on to other women – or other mouths.
At the moment there is no evidence either way regarding mouth infections/overgrowths of BV-causing bacteria, and that being a method of transmission. This doesn’t mean it isn’t happening, but we don’t think it’s a big problem at this stage. We do know BV-causing bacteria can be passed via mouth to vaginas, say if you are a woman having sex with a woman or in a multi-person sexual situation (vaginal-oral/digital-vaginal).
The risk would be that a sexual partner would harbour BV-causing or -contributing bacteria in their mouths, and pass it to a vagina, which means they caught it off another vagina or penis, since penises can harbour BV bacteria and biofilms. This is the case with, say, Helicobacter pylori, the bacteria that causes stomach ulcers. It has been found in genital tracts. We’re not sure what it does in there exactly, but its presence suggests it was passed by mouth to the genitals and may contribute to BV in some women.
But lesbians have more BV and more oral sex!
Research is scant, but two studies have been done on lesbians that give us some clues, though mainly they tell us something we already knew: BV is sexually transmitted (not that BV is sexually transmitted by mouth specifically).
Lesbians have a higher incidence of BV (2.5-fold increased risk), but the link between oral sex and BV has yet to be properly studied and these studies do not detail oral sex specifically as a transmission route from a mouth infection and there is no evidence either way of BV-causing bacteria living in the mouth.
Women who have sex with women share vaginal fluids much more readily than male-to-female sexual partners – the more vaginas around, the more BV is going to appear. These bacteria tend to leave men’s bodies quickly without prolonged contact, but a penis can hang on to it for a while too.
Gardnerella vaginalis has been found in rare cases in some strange places on the body, but this is very uncommon and likely to be found in artificial joints and other areas with artificial implants.
References for studies regarding women who have sex with women and BV
- Characterization of Vaginal Flora and Bacterial Vaginosis in Women Who Have Sex with Women, https://doi.org/10.1086/339884 The Journal of Infectious Diseases, Volume 185, Issue 9, 1 May 2002, Pages 1307–1313,