The educational content in this post, elaborated in collaboration with Lesaffre, was independently developed and approved by the GMFH publishing team and editorial board.

What common situations can disrupt the vaginal microbiota?

Just like all other body mucosae, the vaginal mucosa is colonized by a microbiota that protects it against pathogenic insults. The vaginal microbiota varies between women and has a low diversity because it is dominated by different species of Lactobacilli (Lactobacillus crispatus, L. gasseri, L. iners and L. jensenii).

In addition to a varied microbiota profile between women, it is common for an individual woman’s vaginal microbiota composition to fluctuate over time without showing signs of an unhealthy vaginal state. Also, a vaginal bacterial community with low Lactobacilli content and a high proportion of strictly anaerobic organisms that produce lactic acid has been described in reproductive-age Hispanic and black women and is linked to an unbalanced and asymptomatic state.

 

Factors that can change vaginal mucosa pH and lead to an imbalance of vaginal microbiota include:

  • ethnic origin,
  • hormone fluctuations, typical in pregnancy, lactation and menopause or induced by contraceptives,
  • sexual behavior (i.e., having new sexual partners, frequent change of sexual partners),
  • aggressive or incorrect hygiene (e.g., vaginal douching),
  • antibiotics,
  • a decrease in immunity (e.g., HIV infection),
  • some drugs (e.g., chemotherapy or corticosteroids),
  • stress,
  • and some diseases (e.g., diabetes).

When Lactobacilli numbers fall, other bacteria or yeast normally present in the vagina can overgrow, causing various types of imbalance, including bacterial vaginosis (BV) and vulvovaginal candidiasis (VVC).

 

Can probiotics balance the vaginal microbiome and help manage BV?

BV is a common dysbiosis of the vaginal microbiota characterized by diverse, predominantly anaerobic bacteria, such as Gardnerella vaginalis, Prevotella species and Mobiluncus species, and relatively low numbers of Lactobacillus species.

BV is common in women and up to 50% of cases are asymptomatic. In women with symptomatology, the main signs of BV include itchiness around the vulva, a thin gray-white discharge and a “fishy” odor. BV can also increase the risk of sexual transmitted infections and has been associated with preterm birth.

While antibiotics are currently the recommended treatment for BV, they come with side effects, including an imbalance of the vaginal microbiota that can lead to recurrent infections. However, according to recent systematic reviews and meta-analysis (here; here; here), bacteria and yeast probiotics have shown evidence of being potential prophylactic agents or adjuvant treatments for BV alongside conventional antibiotics.

  • Some Lactobacillus-containing probiotics have shown benefits in preventing and treating bacterial vaginosis with a variable degree of efficacy.
  • The orally administered yeast probiotic Saccharomyces cerevisiae CNCM I-3856 migrates from intestine to vagina, where it may exert its benefits against bacteria involved in BV (here; here; here).

It is important to highlight that the efficacy of probiotics varies with administration route and dosage. For instance, oral administration of probiotics seems to be more effective than vaginal application in treating BV because oral probiotics (bacteria or yeast) are able to migrate from intestine to vagina and eliminate the intestinal pathogens that may be responsible for vaginal infection recurrence. In addition, the oral route for administering probiotics is also the easiest and more convenient way of giving a treatment, which may improve treatment compliance and efficacy. Some probiotics have also been shown to reduce BV recurrences 11 months after treatment.

Some of the mechanisms of action that explain the rationale of using probiotics for BV include direct interference with pathogens’ adherence to vaginal tissues, inhibition of sialidase activity and reduction of vaginal epithelial exfoliation.

Beyond probiotics, combining probiotics with antibiotics and performing vaginal microbiome transplants are both ongoing approaches currently being researched with the aim of strengthening vaginal health and preventing BV recurrence.

 

Are probiotics useful for improving antifungal treatment of VVC?

VVC is the most prevalent vaginal infection in the world, which affects about 75% of reproductive age women, with the main causative agent being Candida albicans. Recurrences are common, with 50% of women with VVC having two or more episodes. In contrast to BV, yeast infection is characterized by a white discharge with the consistency of cottage cheese, no vaginal odor, and redness and inflammation of the vulva.

 

Some evidence suggests some probiotics used as adjuvant therapy to antifungal drugs could be effective for treating VVC.

  • Some studies support the benefits of Lactobacillus species for VVC together with antifungal treatments (e.g., reuteri RC-14®, L. rhamnosus GR-1®, L. rhamnosus Lcr35®). However, a 2017 Cochrane review concluded that, overall, low and very low quality evidence shows that probiotics containing Lactobacillus species as an adjuvant therapy did not change the clinical cure rate, as compared to conventional treatment.
  • However, the aforementioned 2017 Cochrane systematic review did not include yeast probiotics. The efficacy of yeast probiotics for treating VVC is supported by recent data in animal models and small intervention studies, such as the case of cerevisiae CNCM I-3856 as a potential agent for managing VVC based on its immuno-modulatory and anti-inflammatory properties (here; here; here; here).

Based on mouse studies, probiotics’ mechanisms of action against vaginal candidiasis include the ability to interfere with the expression of some virulence traits of Candida albicans in the vaginal cavity and to suppress the host inflammatory response mediated by the influx of neutrophils caused by the fungus into the vagina.

 

Concluding remarks

Bacterial vaginosis and vulvovaginal candidiasis are common dysbiosis of the vaginal microbiota characterized by relatively low numbers of Lactobacillus species.

The evidence for probiotic (bacteria or yeast) treatment of bacterial vaginosis is more compelling compared to vulvovaginal candidiasis. While some yeast probiotics have shown promising benefits for vulvovaginal candidiasis, more research is needed before broad conclusions could be drawn.

Furthermore, increasing evidence suggests that oral consumption of probiotics may be preferred over vaginal administration for vaginal health.

 

 

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