Resistance of clinically important yeasts to antifungal agents.

Resistance of yeasts to antifungal agents was a relatively minor clinical problem for many years. Recently Candida albicans isolates resistant to fluconazole have been reported with increasing frequency in the setting of oral infections in HIV-positive patients. Improved standardization of fluconazole susceptibility testing has resulted in demonstrable correlations between yeast resistance in vitro and in vivo for this agent in the AIDS setting. Known resistance mechanisms for azole antifungals include reduced access of the drug to the intracellular sterol demethylase target, probably because of the action of multidrug resistance efflux pumps, and overproduction of that target. Management and prevention of future resistance development requires greater vigilance for surveillance than has been the practice in the past.