Vaginal microbiota dynamics and fungal vulvovaginitis

Between 70% and 75% of women will experience at least one episode of fungal vulvovaginitis—commonly called a vaginal yeast infection or vulvovaginal candidiasis—during their lifetime, with symptoms that may include itching, vulvar pain and abnormal vaginal discharge, and approximately 8% will develop a recurrent form,¹ representing nearly 138 million women worldwide.²

A narrative review published in Current Fungal Infection Reports¹ summarizes recent findings on the interaction between the vaginal microbiota, particularly Lactobacillus, and opportunistic yeasts of the genera Candida and Nakaseomyces. It aims to clarify their role in vaginal health and fungal vaginal infections. The authors advocate replacing the term “vulvovaginal candidiasis” with the broader term “fungal vulvovaginitis” to recognize the clinical role of other species, particularly Nakaseomyces glabratus (formerly Candida glabrata), in recurrent cases and certain cases of fungal vaginitis.

Candida albicans and Nakaseomyces glabratus: two distinct mechanisms

C. albicans remains the most documented species, accounting for 63% to 70% of cases³ of fungal vulvovaginitis or vulvovaginal candidiasis. It invades the mucosa by transitioning to the hyphal form, a process mediated by adhesins and candidalysin, a toxin that activates the inflammasome.

Nakaseomyces glabratus behaves in the opposite way. Several Mexican cohorts cited in the review report that it clearly predominates in recurrent cases, in association with a decrease in Lactobacillus and an increase in Bifidobacterium. Rather than invade, it persists through biofilm formation, resistance to oxidative stress and immune evasion. This partly explains why conventional antifungals often fail and why the species involved should guide management.

Lactobacillus dynamics and risk of recurrence

The loss of dominance of Lactobacillus crispatus — a species associated with vaginal health particularly through its role in acidifying the environment and producing antimicrobial compounds — in favor of less stable or dysbiotic microbial states is associated with reduced stability of the vaginal ecosystem and increased susceptibility to certain vaginal infections. However, L. iners has an ambivalent role: some strains stabilize the microbiota, while others promote dysbiosis and may even facilitate the filamentous growth of C. albicans in certain cases of vaginitis and fungal infection. 

The review also notes that recurrent bacterial vaginosis could trigger recurrent fungal vulvovaginitis by creating a pro-inflammatory environment that disrupts local immune tolerance to yeasts. This proposed mechanism has not yet been formally demonstrated but is consistent with the frequency of bacterial and fungal co-infections reported in the cited cohorts.

Restorative approaches: preclinical data and current limitations

These treatment limitations and post-treatment recurrences have prompted research into approaches to restore the microbiota: vaginal microbiota transplantation (VMT), synthetic bacterial consortia transplantation (SBCT), and probiotics containing L. crispatus. In mice, these strategies have reduced inflammation and helped restore microbiota balance in models of bacterial vaginosis.In women, data on L. crispatus shows that vaginal colonization can be achieved after treatment for bacterial vaginosis. However, these studies focus exclusively on bacterial vaginosis. To date, no data supports the use of these restorative approaches for the treatment of fungal vulvovaginitis itself.

For recurrent cases, the data summarized in the review underscores the importance of considering species other than C. albicans, particularly N. glabratus. Restoring a lactobacillus-dominated microbiota is also a potential strategy for preventing recurrences, but it has yet to be clinically validated in fungal vulvovaginitis.