Uniqueness and variability
The urogenital tract hosts 9% of the human microbiota1. Normally, the vaginal mucosa in women is populated by a microflora most frequently dominated by lactobacilli2.
In addition to ethnic variations3, this flora can be modified under the influence of several physiological parameters such as age, hormones and pregnancy4.
It is also damaged following certain everyday stresses:
- menstrual cycles,
- sexual relations,
- excessive hygiene practices,
- contraceptive methods,
- viral or bacterial infections,
- drug intake especially antibiotics.
Composition and role of the vaginal microbiota
We know that the term ‘vaginal microbiota’ not only includes the Döderlein vaginal flora with 95% of lactobacilli, but also anaerobic agents
- fulfil a protective role (barrier effect) by forming a biofilm at the surface of the vaginal mucosa limiting the adhesion of pathogenic microorganisms responsible for urogenital infections (Candida albicans, Escherichia coli). The vaginal cavity is an acid environment with a pH between 4 and 5. Variation in pH creates favourable conditions for pathogenic microorganisms such as Gardnerella vaginalisto proliferate.
- help to maintain the pH, allowing the acidity of the environment to produce a bacteriostatic effect.
- produce hydrogen peroxide that contributes to inhibiting anaerobic microorganisms.
- stimulate local immune defences.
Defence and life well-being
The health of women’s urogenital mucosa depends on the hormonal state and quality of the vaginal microbiota.
If damaged, this can result in varying intensities of intimate discomfort5.
The vaginal microbiota has a protective role by limiting the adhesion and growth of pathogenic microorganisms, which can cause a sexually-transmitted disease or a bacterial or mycotic infection of the vagina and urinary tract4. These diseases have a major impact on the intimate and socio-professional quality of life6.
Fertility and maternity
Beyond the woman’s intimate comfort and well-being, the vaginal microbiota plays an essential role in reproductive health and pregnancy.
In fact, the woman’s fertility and success of Assisted Reproductive Technology depend well on the quality of her vaginal microbiota1. The latter is also one of the factors determining the outcome of pregnancy and new-born’s health7.
Therefore, keeping the vaginal microbiota in balanced state is now becoming unavoidable for increasing the chances of getting pregnant and ensuring normal development of the future baby.
The vaginal ecosystem at birth and during early childhood
The child’s microbiota is poorly studied, and its impact on health is unknown.
The young girl’s vaginal pH of the young girl changes from birth and until puberty, to become neutral or slightly alkaline.
The adolescent vaginal microbiota
At puberty, hormonal cycles are established and menstruation starts. The newly-produced oestrogen induces the formation of glycogen peaks in the vaginal epithelium, promoting the development of lactic acid-producing bacteria, which are protective to the vaginal ecosystem.
Menstruation has significantly a negative impact on stability of the microbiota, as do sexual relations. Diseases susceptibility may occur during the fluctuations of the vaginal microbiota.
Vaginal microbiota at menopause
Menopause is characterised by reduced oestrogen production resulting in dryness and even atrophy of the vaginal epithelium.
When oestrogen level falls, glycogen content also drops; leading to reduced lactobacilli and increased vaginal pH as glucose is no longer converted into lactic acid.
1 Sirota I, Zarek SM, Segars JH. Potential influence of the microbiome on infertility and assisted reproductive technology. Semin Reprod Med. 2014; 32: 35-42.
2 Aagaard K, Petrosino J, Keitel W, Watson M, Katancik J, Garcia N, Patel S, Cutting M, Madden T, Hamilton H, Harris E, Gevers D, Simone G, McInnes P, Versalovic J. The Human Microbiome Project strategy for comprehensive sampling of the human microbiome and why it matters. FASEB J. 2013; 27: 1012-1022.
3 Ravel J, Gajer P, Abdo Z, Schneider GM, Koenig SS, McCulle SL, Karlebach S, Gorle R, Russell J, Tacket CO, Brotman RM, Davis CC, Ault K, Peralta L, Forney LJ. Vaginal microbiome of reproductive-age women. Proc Natl Acad Sci U S A. 2011; 108 Suppl 1: 4680-4687.
4 Ma B, Forney LJ, Ravel J. Vaginal microbiome: rethinking health and disease. Annu Rev Microbiol. 2012; 66: 371-389.
5 Blaze V. [Non-infectious cystalgias]. Rev Med Brux. 2013; 34: 232-235.
6 Reid G, Bruce AW. Urogenital infections in women: can probiotics help? Postgrad Med J. 2003; 79: 428-432.
7 Farr A, Kiss H, Hagmann M, Machal S, Holzer I, Kueronya V, Husslein PW, Petricevic L. Role of Lactobacillus species in the intermediate vaginal flora in early pregnancy: a retrospective cohort study. PLoS One. 2015; 10: e0144181.