Acquired amphotericin B resistance attributed to a mutated <i>ERG3</i> in <i>Candidozyma auris</i>

First identified in 2009, <i>Candidozyma auris</i> (formerly <i>Candida auris</i>) is an emerging multidrug-resistant fungus that can cause invasive infections with a crude mortality rate ranging from 30 to 60%. Currently, 30-50% of <i>C. auris</i> isolates are intrinsically resistant to amphotericin B. In this study, we characterized a clinical case of acquired amphotericin B resistance using whole-genome sequencing, a large-scale phenotypic screen, comprehensive sterol profiling, and genotypic reversion using CRISPR. Data obtained in this study provide evidence that a deletion resulting in a frameshift in <i>ERG3</i> significantly contributes to the observed resistant phenotype, and a nonsense mutation in <i>ERG4</i> may more modestly contribute to resistance. Characterization of this isolate also revealed that a fitness cost is associated with the abrogation of ergosterol production and its replacement with other late-stage sterols. This article presents a clinical case description of amphotericin B resistance from a frameshift mutation in <i>ERG3</i> in <i>C. auris</i> and marks an advancement in the understanding of antifungal resistance in this fungal pathogen.