Identification and Elimination of Antifungal Tolerance in Candida auris

Antimicrobial resistance is a global health crisis to which pathogenic fungi make a substantial contribution. The human fungal pathogen C. auris is of particular concern due to its rapid spread across the world and its evolution of multidrug resistance. Fluconazole failure in C. auris has 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 in C. auris to all three classes of antifungal drugs used to treat invasive candidiasis. We find that (1) C. auris is tolerant to several common fungistatic and fungicidal drugs, which in some cases can be detected after 24 h, as well as after 48 h, of antifungal drug exposure; (2) the tolerant phenotype reverts to the susceptible phenotype in C. auris; and (3) combining azole, polyene, and echinocandin antifungal drugs with the adjuvant chloroquine in some cases reduces or eliminates tolerance and resistance in patient-derived C. auris isolates. These results suggest that tolerance contributes to treatment failure in C. auris infections 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.

Automated summary

Antimicrobial resistance, particularly in the fungal pathogen C. auris, is a major global health crisis. This study focuses on the antifungal tolerance in C. auris and its contribution to treatment failure. The findings suggest that C. auris is tolerant to various antifungal drugs and combining different drugs with the adjuvant chloroquine may help reduce or eliminate tolerance and resistance in patient-derived isolates. Overall, this study emphasizes the importance of addressing tolerance in C. auris infections and exploring strategies to improve treatment outcomes.