Recurrent Thrush and the Gut Microbiome: What Did Our Research Find?
One of the smaller but interesting parts of my PhD research was looking beyond the vaginal microbiome to ask what was happening in the gut microbiome of people with recurrent thrush/ vulvovaginal candidiasis (RVVC) using fluconazole.
In our published pilot study, we compared both the vaginal and gastrointestinal bacterial and fungal microbiomes of people using fluconazole intermittently or as maintenance therapy with healthy controls. Overall, gut microbiome diversity did not significantly differ between the groups, reassuringly, we didn’t see evidence of some dramatic collapse of gut microbial diversity associated with fluconazole use.
There were, however, some interesting signals.
The maintenance fluconazole group showed differences at the phylum level, including a lower Bacteroidetes to Firmicutes relationship, which raised the possibility that longer term fluconazole exposure may influence gastrointestinal microbial composition. But this was a small exploratory study of only 27 participants, and diet and lifestyle changes commonly made by people trying to manage RVVC could also have contributed. This finding needs investigation in much larger cohorts before we know what it means clinically.
We also found something important that challenges a long standing idea about recurrent thrush: matching Candida species were uncommon between an individual’s gut and vagina. Our findings therefore didn’t support the gut acting as a simple Candida reservoir repeatedly “reinfecting” the vagina.
I set out to explore the long held belief that the gut was the reservoir of re-infection in RVVC, because you know what….we don’t have any studies that show that to be true…And in may ways I was not surprised that the data didn’t confirm the gut to be the issue.
Looking at the gut in someone with RVVC shouldn’t automatically mean trying to “eradicate Candida,” embarking on highly restrictive diets, or assuming every gut microbiome needs fixing. It means recognising that different microbial ecosystems coexist within the same person and are influenced by diet, hormones, immunity, medications and other aspects of the host environment.
Sometimes gastrointestinal symptoms or history might make further assessment worthwhile. Sometimes they won’t.
Our study was a small first step rather than a definitive answer, but it highlights why future RVVC research needs to look beyond individual organisms and even beyond individual body sites.
Microbiomes don’t exist in isolation. Neither do the people carrying them.
Paper: Bradfield Strydom, M., Nelson, T. M., Khan, S., Walpola, R. L., Ware, R. S., & Tiralongo, E. (2025). The impact of fluconazole use on the fungal and bacterial microbiomes in recurrent vulvovaginal candidiasis (RVVC): A pilot study of vaginal and gastrointestinal site interplay. European Journal of Clinical Microbiology & Infectious Diseases, 44, 285–301. HERE
Other relevant research:
Bradfield Strydom, M., Khan, S., Walpola, R. L., Ware, R. S., & Tiralongo, E. (2023). Interplay of the microbiome and antifungal therapy in recurrent vulvovaginal candidiasis (RVVC): A narrative review. Journal of medical microbiology, 72(5), 001705.HERE
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