azolresistens

Azolresistens, or azole resistance, refers to the reduced susceptibility of fungal pathogens to azole antifungals such as fluconazole, itraconazole, voriconazole and posaconazole. Clinically, resistance can lead to treatment failure or persistent infection despite appropriate drug exposure and adequate drug levels. It is an increasing concern in invasive candidiasis and invasive aspergillosis, and can complicate management of other fungal infections.

Mechanisms of resistance are diverse and often multifactorial. They include mutations or upregulation of the azole target enzyme lanosterol 14α-demethylase (ERG11 in Candida, CYP51A in Aspergillus), which reduces drug binding. Overexpression of efflux pumps (such as Cdr1, Cdr2 and Mdr1 in Candida; various ABC and MFS transporters in other species) lowers intracellular drug concentrations. Changes in ergosterol biosynthesis and the formation of biofilms can also decrease azole susceptibility. Environmental exposure to azoles, including agricultural fungicides, can select for resistant strains and contribute to clinical resistance, particularly for Aspergillus fumigatus.

Organisms commonly associated with azole resistance include Candida species (notably Candida glabrata and occasionally Candida albicans with reduced susceptibility) and Aspergillus fumigatus, where cyp51A promoter and coding mutations (such as TR34/L98H or TR46/Y121F/T289A) are well-described. Resistance can spread locally and regionally, posing diagnostic and therapeutic challenges.

Diagnosis relies on antifungal susceptibility testing (CLSI/EUCAST) and, when available, molecular methods to detect resistance mutations. Management often requires switching to non-azole antifungals (echinocandins, amphotericin B) or combination therapy, alongside stewardship measures to reduce unnecessary azole exposure and environmental selection.