The vaginal microbiota is a complex ecosystem that plays a crucial role in women’s gynecological health. During different stages of life, including menopause, significant changes occur in the composition and diversity of these microorganisms, which could lead to a number of health problems, such as bacterial vaginosis and recurrent urinary tract infections.

In recent years, the use of some probiotics has been intensively researched as a potential strategy to improve the health of the vaginal microbiota in postmenopausal women. This article will examine the current scientific evidence on the role of probiotics in promoting a healthy vaginal microbiota.

The vaginal microbiota in postmenopausal women

Menopause is characterized by a decrease in estrogen levels, which has a direct impact on the vaginal environment. This hormonal change due to age leads to changes in vaginal pH, a reduction in vaginal glycogen production, and a decrease in the amount of lactobacilli, beneficial bacteria that are critical to maintaining a healthy vaginal environment. This alteration predisposes postmenopausal women to an increased susceptibility to vaginal infections and disorders.

The scientific community agrees that a global concept of normality versus dysbiosis of the vaginal microbiome is debatable. This is due to the fact that women of different ethnicities have a unique vaginal microbiota with regional variations corresponding to the ecosystem in which they interact. That said, we can say that the vaginal microbiome is a highly differentiated and dynamic environment affected by the stages of a woman’s life, such as gestational status, menstrual cycle, sexual activity, age and contraceptive use.

In recent years, the understanding of the composition and structure of the vaginal bacterial community has expanded significantly as a result of the resulting investigations using culture-independent methods based on the analysis of sequences of the 16S ribosomal RNA (rRNA) gene. In asymptomatic and otherwise healthy women, there are several types of vaginal microbiota, most often dominated by Lactobacillus species, while others are composed of a wide range of anaerobic microorganisms. https://doi.org/10.1146/annurev-micro-092611-150157

Scientific evidence

Probiotics are live microorganisms that, when administered in adequate amounts, confer health benefits to the host. More specifically, certain strains of lactobacilli, such as Lactobacillus rhamnosus and Lactobacillus reuteri, have been shown to be able to colonize the vagina and restore the balance of the microbiota in postmenopausal women.

Specifically, the human vaginal microbiome is dominated by Lactobacillus spp., which typically comprises more than 70% of the bacteria resident in females, compared to 1% in other mammals. These lactobacilli process glycogen and its breakdown products to produce lactic acid, leading to an exceptionally low vaginal pH of ≤4,5. DOI: 10.1128/IAI.67.10.5170-5175.1999

Numerous clinical studies have investigated the effect of probiotics on the vaginal health of postmenopausal women. A recent published meta-analysis analyzed the results of several randomized controlled clinical trials and found that probiotic supplementation was associated with a significant reduction in the incidence of bacterial vaginosis and an improvement in the symptoms of vaginal atrophy in postmenopausal women. https://doi.org/10.31219/osf.io/a7hky

In addition, probiotics have been shown to reduce the colonization of vaginal pathogens, such as Candida albicans and Gardnerella vaginalis, by competing for binding sites in the vaginal mucosa and producing metabolites that inhibit their growth. This suggests that probiotics can not only restore the balance of the vaginal microbiota, but also prevent recurrent infections.

Mechanisms of action

Probiotics exert their beneficial effects on the vaginal microbiota through several mechanisms. These include the production of lactic acid and hydrogen peroxide, which lower vaginal pH and create an inhospitable environment for pathogens, as well as competition for nutrients and binding sites in the vaginal mucosa, which prevents the colonization of harmful bacteria.

• Lactic acid and hydrogen peroxide production: Probiotic strains, especially lactobacilli, have the ability to ferment carbohydrates available in the vagina into lactic acid. Lactic acid lowers vaginal pH, creating an acidic environment that is unfavorable for the growth of pathogenic bacteria. In addition, some lactobacilli also produce hydrogen peroxide, which has antimicrobial properties and can help eliminate unwanted microorganisms.
• Competition for nutrients: Probiotics compete with pathogenic bacteria for nutrients available in the vagina. By consuming the resources necessary for the growth and survival of pathogens, probiotics can limit their proliferation and colonization in the vaginal mucosa.
• Competition for binding sites: Probiotic strains can compete with pathogens for binding sites on the vaginal mucosa. By attaching to the epithelial cells of the vagina, probiotics prevent pathogenic microorganisms from attaching to and colonizing the mucosa, reducing the risk of infections.
• Production of antimicrobial metabolites: In addition to lactic acid and hydrogen peroxide, probiotics can produce a variety of metabolites with antimicrobial properties, such as bacteriocins and short-chain fatty acids. These substances help inhibit the growth of pathogenic bacteria and maintain a healthy balance in the vaginal microbiota.

Together, these mechanisms contribute to the ability of probiotics to promote a balanced vaginal microbiota and reduce the risk of infections and gynecological disorders in postmenopausal women. Understanding these mechanisms is critical for the development of probiotic-based therapeutic strategies and for optimizing their effectiveness in the treatment and prevention of vaginal health-related diseases. https://doi.org/10.1371/journal.pone.0104511

Promising new developments

Although not specific to vaginosis, elevated pH is a condition commonly used to diagnose it. An ideal treatment would target Gardnerella and other undesirable bacteria while also promoting a favorable pH environment for probiotics. One idea might be to apply beneficial bacteria such as L. crispatus as a probiotic treatment to achieve proactive prevention of recurrence by producing antibacterial agents and restoring healthy vaginal flora.

However, there are limitations to probiotic administration ensuring efficacy, including frequent, if not daily, applications that present a challenge to user adherence. Therefore, sustained administration of probiotics through a single treatment would be highly desirable. Recently, 3D bioprinted supports have been proposed that use bioink that includes probiotics for the sustained recovery of L. crispatus in the female reproductive tract. The characteristics of a print, such as geometry, load, composition, viscosity and degradation, can be precisely tailored to meet a specific need.

While 3D printing has shown promising results in engineering cartilage, other soft tissues, and delivering antiviral drugs through intravaginal rings, localized delivery for the treatment of vaginosis has only recently been explored.

Although it is a model under study, it offers a further step towards the most effective compliance with the therapeutic reference points for the treatment of this alteration. https://doi.org/10.1016/j.stlm.2023.100120

Conclusion

On numerous occasions we have seen that probiotics represent a promising strategy to improve health, both in the intestinal ecosystem and the vaginal microbiota, including that present in postmenopausal women. Scientific evidence suggests that probiotic supplementation can help restore microbiota balance, prevent recurrent vaginal infections, and improve symptoms of vaginal atrophy.

There are very promising solutions still under study, but everything indicates that in the not too distant future we will be able to access this type of solution in a specific way.

However, more research is needed to confirm these findings and establish clear clinical guidelines for the use of spot probiotics in this spot population.