Study shows rise in fluconazole-resistant C. albicans vaginal infections

Key takeaways

• The incidence of fluconazole-resistant Candida albicans is more common than previously thought.
• The resistance is likely driven by more frequent uses of fluconazole and over-the-counter antifungals.
• Boric acid as a treatment regimen leads to high cure rates and low recurrence rates.

The prevalence of fluconazole-resistant Candida albicans vulvovaginal candidiasis is on the rise, according to research presented at the Infectious Diseases Society for Obstetrics and Gynecology meeting, but boric acid may help.

Vulvovaginal candidiasis (VVC) — a fungal infection that impacts about 75% of women at least once and roughly 50% twice in their lifetime — is most often caused by C. albicans, according to Ryan Sobel, MD, a clinical assistant professor and co-director of the Jefferson Vulvovaginal Health Center at Thomas Jefferson University, and colleagues. The CDC’s treatment recommendation for recurrent VVC is fluconazole induction therapy (three 150 mg doses every 3 days) and a 6-month maintenance prophylactic regimen. Even so, the researchers noted that common usage has led to a “growing concern” for fluconazole-resistant C. albicans VVC (FRVVC).

To assess the frequency of FRVVC, Sobel and colleagues conducted a retrospective review of patients diagnosed with C. albicans VVC at the Jefferson Vulvovaginal Health Center between November 2019 and December 2021. They also sought alternative treatments, evaluating how effective boric acid might be.

Previously, others have reported that the incidence of FRVVC ranges from 0.5% to 2%, the researchers wrote. However, they found that 71 out of 970 patients — 7.3% — in their study had FRVVC.

Additionally, 16.1% of the 31 patients who underwent antifungal susceptibility testing had results that suggested a dose-dependent or susceptible strain.

Sobel and colleagues also reported that boric acid appeared to be an effective treatment for fluconazole-resistant VVC, “leading to high cure rates and low recurrence rates.”

In an analysis of treatment success by boric acid duration, the researchers found that seven of 10 patients had been clinically cured in fewer than 21 days of treatment. Between 22 and 30 days of treatment led to a clinical cure rate of 81.3% (13 of 16 cured).

There was a smaller group for the researchers to evaluate when it came to recurrence rates after boric acid treatment, but the researchers found that three of the six patients had been clinically cured less than 30 days since the last dose. After 30 days, only one patient had been clinically cured.

Sobel told Healio that the increase in resistance is “likely due to more pervasive uses of fluconazole, as well as over-the-counter antifungals, both of which are often prescribed without first confirming the presence of yeast.” It is important for primary care providers to confirm the presence of yeast “before empirically prescribing antifungal medication,” he said.

Providers should also be aware of resistance to antifungal therapy, Sobel said.

“If a woman's symptoms are not responding to antifungal therapy, they should have a suspicion for the possibility that they may have a resistant strain of yeast — at which time, it is even more important to confirm the presence of yeast, as well as obtain antifungal susceptibility testing,” he said.