Research has shown that the vaginal microbiome might be a factor in the risk of contracting Sexually transmitted infections (STIs).

We do know that women diagnosed with Chlamydia are more likely to have a vaginal microbiome composition that is associated with less benefits. The way these studies are typically conducted means we don’t know if the presence of the STI impacts the microbiome or if the women already had that less beneficial microbiome and that made the more likely to contract the STI on exposure. We do know that HIV transmission is increased in women who have a dysbiotic (disrupted) vaginal microbiome, or a vaginal microbiome that has less of the Lactobacilli species that are typically the most beneficial.

Overall, because we know there are many ways a beneficial vaginal microbiota can contribute to a healthy status, it is likely that a healthy microbiota might have some protective effect against STIs. 

What components of vaginal microbiome are the most beneficial to protect against STIs?

Overall,  the research to date suggests that vaginal microbiome is factor in risk of contracting and passing on sexually transmitted infections. There are multiple ways in which a beneficial microbiome composition in the vaginal can protect against pathogens. Firstly, by having the right abundance of these organisms means new organisms find it hard to compete for space and nutrients. Some lactobacilli produce acidic conditions that pathogenic organisms find it harder to survive, and just the acidity of the vaginal can be an indicator of a healthy status. The protection goes beyond producing the acidic conditions, as some vaginal lactobacilli produce a molecule that kills other bacteria including pathogens and STIs (called a bacteriocin). Microorganisms have developed ways to ‘talk’ to our own human cells and this means they can influence the host environment. We now know that Lactobacilli, especially L.  crispatus -  a species known to be beneficial in the vaginal microbiome, can ‘talk’ to our cells and change their response to pathogens and increase our own defence mechanisms.

What does the new research show women should consider about their vaginal microbiome, and which lifestyle factors should be adjusted to accommodate protection against STIs?

Protection against exposure, condoms(!) is the best way to reduce your risk of contracting sexually transmitted infections. If you are sexually active and or have new sexual partner(s) you should get tested for sexually transmitted infections. Condom usage might also help maintain a healthy vaginal microbiome, as semen shifts the pH away from the healthy acidic status, and other sexual practices also can shift your vaginal microbiome composition. So consider condom usage as part of your overall vaginal health, although lubricants that many women need to use with condoms can also contain antibacterial compounds and compounds that shift the pH of your vagina. Your best approach is to consider your vaginal status and monitor symptoms (discomfort, odor, itch) and determine the best products for you. Don’t be afraid to experiment and find the right solutions for your sexual practices. 

Professor Willa Huston is a microbiologist at the University of Technology Sydney. She leads a research team who investigate sexually transmitted infections and the reproductive tract microbiome. Her research team is committed to understanding how STIs and the vaginal microbiome are involved in infertility and other adverse impacts on women’s reproductive and genital health. Ultimately the team aims to develop ways to diagnose, treat, and prevent these impacts, improving women’s reproductive and sexual health.