What You Should Know About the Vaginal Microbiome

When we hear about the human microbiome, the gut often steals the spotlight. But there’s another fascinating microbial world that lives inside roughly half the population—the vaginal microbiome. This community is comprised primarily of bacteria but also includes viruses, fungi and other microbes that work together to support a healthy vaginal microenvironment. It is early days for studies about the vaginal microbiome, but we are already beginning to gain a great appreciation for its importance in women’s health.

Key players of a healthy vaginal microbiome

The beneficial bacteria inhabiting the vagina serve as a first line of defence against pathogens, helping to keep harmful bacteria and yeast at bay—just like the gut, skin and oral microbiomes.

However, unlike these other microbiomes, microbial diversity is not considered a sign of a healthy vaginal microbiome. Instead, vaginal microbial communities of healthy women are mostly dominated by a single, very important group of bacteria called Lactobacillus (or lactobacilli). And with good reason; lactobacilli perform several specific functions to help maintain a healthy vaginal microenvironment. Lactobacilli can:

• Produce lactic acid, which keeps the vaginal environment slightly acidic (a pH of around 3.8-4.5). This acidity is crucial because it prevents harmful bacteria from growing and causing infections^1,2.
• Produce hydrogen peroxide and a type of natural antimicrobial compound called bacteriocins, both of which can help fight off harmful bacteria^3,4.
• Attach themselves to a type of cell found in the vaginal lining called epithelial cells. By taking up valuable real estate in the vaginal wall, the lactobacilli leave little room for harmful bacteria to attach and grow^1,2.
• Interact with the human immune system to help stimulate the production of antimicrobial compounds that target harmful bacteria. This interaction enhances the body’s natural defences, making it even harder for harmful bacteria to establish an infection.

There are several different species of lactobacilli found in the vaginal microbiome, including Lactobacillus crispatus, L. gasseri, L. iners, and L. jensenii.  Each of these, as well as other bacteria that are present in smaller numbers, play a specific role in maintaining the balance and health of the vaginal ecosystem.

What happens when the balance is disrupted?

The vaginal microbial community in some women is highly diverse, lacking a dominant Lactobacillus species. A more instable, diverse community that is depleted in lactobacilli has been associated with an increased risk of bacterial vaginosis (BV), an infection of the lower genital tract that affects nearly 30 per cent of women worldwide⁵. BV increases the risk of potentially negative reproductive health outcomes, including infections caused by sexually transmitted pathogens, reduced fertility, and complications of pregnancy⁶.

There is still a lot we don’t know about the specific role microbes play in women’s reproductive and overall health. Researchers are working hard to better understand the vaginal microbiome so that we can develop new ways to diagnose, treat and prevent a range of women’s health conditions, including BV.

Factors influencing the vaginal microbiome

The composition of the vaginal microbiome is unique to each woman and can be influenced by things like sexual activity, female hygiene practices, stress, geography and race. One of the biggest factors shaping the vaginal microbiome is hormonal changes throughout life, particularly during puberty, menstruation, pregnancy and menopause^7,8. This is because of an interesting relationship between estrogen and the microbiome. Estrogen in the body stimulates cells in the lining of the vaginal wall to produce a type of sugar called glycogen. This glycogen provides a nourishing food source for beneficial lactobacilli, which they use to produce lactic acid and other compounds that inhibit the growth of potentially harmful bacteria. This is why fluctuations in estrogen throughout a woman’s life directly influence the composition of the vaginal microbiome.

How to promote a healthy vaginal flora

While researchers are still working hard to figure out exactly how to optimise the health of the vaginal microbiome, there are some simple practices that can help maintain your microbiome (and overall) health⁹:

Make healthy lifestyle choices: The things we know are good for us, like avoiding smoking, reducing stress, and eating a diverse, nutrient-rich diet, are all thought to be good for our vaginal microbiome.

Let Mother Nature do her work: The vagina cleans itself naturally, so stay away from antimicrobial cleansing products and douching. These can disrupt the natural balance of the vaginal flora and increase risk of BV.

Practice safe sex: Use protection and practice safe sex to reduce the risk of introducing harmful microorganisms.

The take-away

The vaginal microbiome hasn’t received due credit for all it does to promote women’s health and well-being, from protecting against infections and helping regulate the immune system to supporting reproductive functions. At the AHMB, we are collecting vaginal microbiome samples so that we can continue to advance our understanding of this vital part of women’s health.

 

References

1. Chee, W. J. Y., Chew, S. Y. & Than, L. T. L. Vaginal microbiota and the potential of Lactobacillus derivatives in maintaining vaginal health. Microbial Cell Factories 19, 203, doi:10.1186/s12934-020-01464-4 (2020).
2. Amabebe, E. & Anumba, D. O. C. The Vaginal Microenvironment: The Physiologic Role of Lactobacilli. Frontiers in Medicine 5, doi:10.3389/fmed.2018.00181 (2018).
3. Miko, E. & Barakonyi, A. The Role of Hydrogen-Peroxide (H2O2) Produced by Vaginal Microbiota in Female Reproductive Health. Antioxidants 12, 1055 (2023).
4. Stoyancheva, G., Marzotto, M., Dellaglio, F. & Torriani, S. Bacteriocin production and gene sequencing analysis from vaginal Lactobacillus strains. Archives of Microbiology 196, 645-653, doi:10.1007/s00203-014-1003-1 (2014).
5. Peebles, K., Velloza, J., Balkus, J. E., McClelland, R. S. & Barnabas, R. V. High Global Burden and Costs of Bacterial Vaginosis: A Systematic Review and Meta-Analysis. Sexually Transmitted Diseases 46 (2019).
6. Chen, X., Lu, Y., Chen, T. & Li, R. The Female Vaginal Microbiome in Health and Bacterial Vaginosis. Frontiers in Cellular and Infection Microbiology 11, doi:10.3389/fcimb.2021.631972 (2021).
7. Kaur, H., Merchant, M., Haque, M. M. & Mande, S. S. Crosstalk Between Female Gonadal Hormones and Vaginal Microbiota Across Various Phases of Women’s Gynecological Lifecycle. Frontiers in Microbiology 11 (2020).
8. Auriemma, R. S. et al. The Vaginal Microbiome: A Long Urogenital Colonization Throughout Woman Life. Frontiers in Cellular and Infection Microbiology 11, doi:10.3389/fcimb.2021.686167 (2021).
9. Lehtoranta, L., Ala-Jaakkola, R., Laitila, A. & Maukonen, J. Healthy Vaginal Microbiota and Influence of Probiotics Across the Female Life Span. Front Microbiol 13, 819958, doi:10.3389/fmicb.2022.819958 (2022).

 

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