Azole Resistance in Dermatophytes

Azole antifungal agents (eg, fluconazole and itraconazole) have been widely used to treat superficial fungal infections caused by dermatophytes and, unlike the allylamines (such as terbinafine and naftifine), have been associated with resistance development. Although many published manuscripts describe resistance to azoles among yeast and molds, reports describing resistance of dermatophytes are starting to appear. In this review, I discuss the mode of action of azole antifungals and mechanisms underlying their resistance compared with the allylamine class of compounds. Data from published and original studies were compared and summarized, and their clinical implications are discussed. In contrast to the cidal allylamines, static drugs such as azoles permit the occurrence of mutations in enzymes involved in ergosterol biosynthesis, and the ergosterol precursors accumulating as a consequence of azole action are not toxic. Azole antifungals, unlike allylamines, potentiate resistance development in dermatophytes.