Antagonism of Fluconazole and a Proton Pump Inhibitor against Candida albicans.

Hospitalized ill patients, at risk for invasive candidiasis, often receive multiple medications, including proton pump inhibitors (PPIs). The antifungal fluconazole perturbs the vacuolar proton ATPase. The PPI omeprazole antagonized Candida albicans growth inhibition by fluconazole. A C. albicans codon-adapted pHluorin, Ca.pHluorin, was generated to measure cytosolic pH. The fungal cytosol was acidified by omeprazole and realkalinized by coexposure to fluconazole. Vacuolar pH was alkalinized by fluconazole. Off-target effects of any medication on fungal pathogens may occur.