Bacterial vaginosis: are men involved?
Bacterial vaginosis, linked to an imbalance in the vaginal microbiota, may be caused by bacteria present in the penile microbiota of some men and transmitted during sexual intercourse.
Bacterial vaginosis (BV) is a highly common infection. Often displaying few symptoms, the disease can have serious consequences, increasing the risk of sexually transmitted infections (including HIV) and complications during pregnancy (preterm delivery, preterm labor, and late miscarriage). Treatment with long-term efficacy is lacking and BV recurs in up to 50% of women at 6–12 months following treatment.
Bacteria nesting under the foreskin
Do some men play a role, via their penile microbiota, in the development of BV in their partner? Numerous studies support this hypothesis, including those showing a lower frequency of BV (-40%) in women who have sex with circumcised men*. As the skin covered by the foreskin is particularly rich in bacteria associated with bacterial vaginosis, certain scientists believe circumcision to be a prevention factor.
The same species are found in penile and vaginal microbiota
A team of researchers followed 168 heterosexual couples, where the female partner was free of infection at the outset of the study. After one year of follow-up, nearly one in three women had developed bacterial vaginosis. According to the analyses, BV occurrence seemed to be directly related to the composition of the penile microbiota. The authors identified seven bacterial species whose presence accurately predicted the occurrence of bacterial vaginosis. Several of these species were also found in the vaginal microbiota of infected women.
Treat men to protect women?
These results led the researchers to put forward two hypotheses: either bacteria from the penile microbiota are transmitted directly during sexual intercourse, or they disrupt the vaginal flora and cause infection over the long term. In either scenario, the researchers advocate the inclusion of male partners when treating infected women and suggest evaluating a treatment that, by modifying the microbiota of the penis, would prevent the occurrence or recurrence of bacterial vaginosis.
* Gray, R. H., Kigozi, G., Serwadda, et al. The effects of male circumcision on female partners’ genital tract symptoms and vaginal infections in a randomized trial in Rakai, Uganda. Am J Obstet Gynecol. 2009 Jan;200(1):42.e1-7.
Mehta SD, Zhao D, Green SJ et al. The Microbiome Composition of a Man's Penis Predicts Incident Bacterial Vaginosis in His Female Sex Partner With High Accuracy. Front Cell Infect Microbiol. 2020 Aug 4;10:433. .https://doi.org/10.3389/fcimb.2020.00433