Precise genome editing underlines the distinct contributions of mutations in ERG11 , ERG3 , MRR1 , and TAC1 genes to antifungal resistance in Candida parapsilosis

has recently emerged as a major threat due to the worldwide emergence of fluconazole-resistant strains causing clonal outbreaks in hospitals and poses a therapeutic challenge due to the limited antifungal armamentarium. Here, we used precise genome editing using CRISPR-Cas9 to gain further insights into the contribution of mutations in , , , and genes and the influence of allelic dosage to antifungal resistance in . Seven of the most common amino acid substitutions previously reported in fluconazole-resistant clinical isolates (including Y132F in ) were engineered in two fluconazole-susceptible lineages (ATCC 22019 and STZ5). Each mutant was then challenged against a large array of antifungals, with a focus on azoles. Any possible change in virulence was also assessed in a model. We successfully generated a total of 19 different mutants, using CRISPR-Cas9. Except for R398I ( ), all remaining amino acid substitutions conferred reduced susceptibility to fluconazole. However, the impact on fluconazole susceptibility varied greatly according to the engineered mutation, the stronger impact being noted for G583R acting as a gain-of-function mutation in . Cross-resistance with newer azoles, non-medical azoles, but also non-azole antifungals such as flucytosine, was occasionally noted. Posaconazole and isavuconazole remained the most active . Except for G583R, no fitness cost was associated with the acquisition of fluconazole resistance. We highlight the distinct contributions of amino acid substitutions in , , , and genes to antifungal resistance in .