Relationship between MIC and Minimum Sterol 14α-Demethylation-Inhibitory Concentration as a Factor in Evaluating Activities of Azoles against Various Fungal Species

Abstract

ABSTRACT The minimum growth-inhibitory concentrations (MICs) of azole antifungals were compared to their minimum sterol 14α-demethylation-inhibitory concentrations (MDICs) for clinical fungal isolates. The ascomycetous Candida yeasts tested were clearly divided into two groups: group I, consisting of C. albicans , C. tropicalis , and C. lusitaniae , had MICs that were much higher than the MDICs, whereas group II, comprising C. glabrata , C. parapsilosis , C. guilliermondii , and C. krusei , had MICs that were approximately equal to the MDICs. In the ascomycetous fungi Aspergillus fumigatus and Sporothrix schenckii , the MICs were indistinguishable from the MDICs. In the basidiomycetous fungi Cryptococcus ( Filobasidiella ) neoformans , C. curvatus , and Trichosporon asahii , the MICs and the MDICs were practically identical. These results support the notion that there are two distinct classes of fungi differing in their degree of tolerance to sterol 14α-demethylation deficiency. These findings have significant implications for both fungal physiology and antifungal chemotherapy.