Treatment of Vaginal Candida krusei Infection
For vaginal Candida krusei infection, topical intravaginal boric acid (600 mg once or twice daily for 14 days) is the treatment of choice, as C. krusei is intrinsically resistant to fluconazole and shows variable resistance to other azole antifungals. 1, 2, 3, 4
Understanding C. krusei Resistance
C. krusei should be considered inherently resistant to fluconazole due to reduced sensitivity of the target enzyme to inhibition, making standard fluconazole therapy ineffective both in vitro and clinically 2, 3, 4
C. krusei vaginal isolates demonstrate resistance not only to fluconazole but frequently also to miconazole, ketoconazole, and other azole agents, though clotrimazole shows the best in vitro activity among azoles (MIC90 of 0.25 mcg/mL) 5, 4
Despite itraconazole showing in vitro activity, clinical treatment often fails to achieve mycologic or symptomatic remission 3
First-Line Treatment Approach
Intravaginal boric acid 600 mg once or twice daily for 14 days is recommended as the primary treatment, with clinical and mycological cure achieved in 4 of 6 patients (67%) in published case series 1, 4
Alternative topical options include nystatin intravaginal suppositories or topical 17% flucytosine cream (alone or combined with 3% amphotericin B cream), though availability varies by region 1
Topical imidazoles (particularly clotrimazole) or ciclopirox olamine may be attempted as they show better in vitro activity than triazoles, though clinical evidence is limited 6, 7
Systemic Treatment Options (When Topical Therapy Fails)
High-dose oral fluconazole (800 mg daily for 2-3 weeks) is recommended in Germany when boric acid is unavailable, though this contradicts the known resistance pattern and should be considered suboptimal 6, 7
Oral posaconazole (400 mg twice daily for 3 days, then 400 mg daily) combined with local ciclopirox olamine or nystatin for 15 days has been discussed for refractory cases 7
Newer antifungal agents (oteseconazole and ibrexafungerp) are being evaluated for refractory non-albicans Candida vaginitis, though clinical data remain limited 3
Critical Clinical Considerations
C. krusei vaginitis presents with symptoms indistinguishable from other Candida species (pruritus, burning, erythema, discharge) but is characterized by refractoriness to standard azole therapy 4
Patients with C. krusei vaginitis typically have received multiple prior courses of fluconazole and other antimycotics before correct species identification 4
Vaginal culture with species identification and antifungal susceptibility testing is essential for patients with refractory vulvovaginal candidiasis to guide appropriate therapy 1, 3
Perineal laceration and increased age (>50 years) are significant predictors of C. krusei in vaginal samples 5
Common Pitfalls to Avoid
Do not prescribe fluconazole for documented C. krusei vaginitis, as this represents intrinsic resistance and will result in treatment failure 2, 3, 4
Avoid assuming all vaginal Candida infections are C. albicans—approximately 5-10% are non-albicans species, with C. krusei representing about 1% of vulvovaginal candidiasis cases 6, 5
Do not rely on clinical presentation alone to distinguish C. krusei from other Candida species, as symptoms are nonspecific and laboratory confirmation is mandatory 1
Be aware that successive isolates from the same patient typically represent relapses rather than reinfection, indicating need for more aggressive or prolonged therapy 4
Treatment Monitoring
Boric acid emerged as the definitive treatment method of choice despite availability of newer antifungal agents, based on clinical experience 3
All C. krusei isolates tested showed susceptibility to amphotericin B, caspofungin, ketoconazole, and miconazole in vitro, though clinical correlation for vaginal infections is limited 5
Antifungal susceptibility testing should be performed for C. krusei isolates, particularly in cases failing initial non-fluconazole therapy 5, 3