Impact of pH on the antifungal susceptibility of vaginal Candida albicans

Objective: To investigate the antifungal susceptibility at pH 7.0 and pH 4.0 of 5 antifungal agents against Candida albicans isolated from patients with vulvovaginal candidiasis. Methods: Antifungal susceptibility testing at pH 7.0 and pH 4.0 was performed using the broth microdilution method (CISI, document M27-A2). Results: The minimal inhibitory concentrations (MICs) of miconazole, clotrimazole, fluconazole, and nystatin against C. albicans at pH 4.0 were significantly higher than those at pH 7.0 (0.25 vs 0.03 mu g/mL, 0.50 vs 0.03 mu g/mL, 0.50 vs 0.25 mu g/mL, and 32 vs 2 mu g/mL, respectively; P<0.001), whereas the MIC of itraconazole at pH 4.0 was lower than that at pH 7.0 (0.030 vs 0.125 mu g/mL; P<0.001). The susceptibility rate of C albicans to itraconazole at pH 4.0 was significantly higher than at pH 7.0 (95.0% vs 51.7%; P<0.001). The susceptibility rate to itraconazole at pH 7.0 was significantly lower than the susceptibility rate to fluconazole (51.7% vs 100.0%; P<0.001), whereas the susceptibility rates to the 2 drugs were similar at pH 4.0 (95.0% and 96.7%, respectively). Conclusion: Media at different pH values should be used for sensitivity tests according to the environment of C. albicans. Crown Copyright (C) 2011 Published by Elsevier Ireland Ltd. on behalf of International Federation of Gynecology and Obstetrics. All rights reserved.