Identification and Elimination of Antifungal Tolerance inCandida auris

Abstract

Antimicrobial resistance is a global health crisis to which pathogenic fungi make a substantial contribution. The human fungal pathogenC. aurisis of particular concern due to its rapid spread across the world and its evolution of multidrug resistance. Fluconazole failure inC. aurishas been recently attributed to antifungal ``tolerance''. Tolerance is a phenomenon whereby a slow growing subpopulation of tolerant cells, which are genetically identical to susceptible cells, emerges during drug treatment. We use microbroth dilution and disk diffusion assays together with image analysis to investigate antifungal tolerance inC. auristo all three classes of antifungal drugs used to treat invasive candidiasis. We find that 1)C. aurisis tolerant to several common fungistatic and fungicidal drugs, which in some cases can be visually detected after 24 hours, as well as after 48 hours, of antifungal drug exposure; 2) the tolerant phenotype reverts to the susceptible phenotype inC. auris; and 3) combining azole, polyene, and echinocandin antifungal drugs with the adjuvant chloroquine reduces or eliminates tolerance and resistance in patient-derivedC. aurisisolates. These results suggest that tolerance contributes to treatment failure inC. aurisinfections for a broad range of antifungal drugs and that antifungal adjuvants may improve treatment outcomes for patients infected with antifungal-tolerant or antifungal-resistant fungal pathogens.