# Decoding resistance in Diutina catenulata by validating clinically relevant Erg11/Fks1 mutations

## TL;DR

This study identifies specific gene mutations in Diutina catenulata that cause resistance to antifungal drugs, with resistance levels influenced by environmental conditions.

## Contribution

The study validates clinically relevant ERG11 and FKS1 mutations in Diutina catenulata and reveals their resistance mechanisms through functional and structural analysis.

## Key findings

- ERG11-F126L mutation increases fluconazole resistance 21-fold in SD-Ura medium.
- FKS1 mutations increase echinocandin resistance by 1.4 to 2-fold.
- Molecular docking shows mutations alter drug-binding sites and ATP domains.

## Abstract

To verify the causal relationship between specific mutations in the ERG11 and FKS1 genes and antifungal drug resistance in clinical isolates of Diutina catenulata.

Recombinant plasmids expressing mutant alleles of ERG11 (F126L, K143R) or FKS1 (F621I, S1123G, I1348S, and the triple mutant S625L/S1123G/F1354L) were constructed and functionally validated in a Saccharomyces cerevisiae W303-1a model. Susceptibility testing was performed under different nutrient conditions (SD-Ura and YPD). Molecular docking analysis was conducted to elucidate the structural mechanisms of resistance.

Functional validation in S. cerevisiae confirmed that both ERG11 and FKS1 mutations conferred resistance in a nutrient-dependent manner. The ERG11-F126L mutation increased the fluconazole MIC by 21-fold in SD-Ura compared to YPD. FKS1 mutations led to 1.4 to 2-fold increases in echinocandin MICs. Molecular docking revealed the mechanistic bases: ERG11-F126L expanded the ligand-binding cavity (ΔΔG +1.2 kcal/mol), FKS1-F621I disrupted hydrophobic interactions, and compound mutations synergistically perturbed ATP-binding domains.

Specific mutations in ERG11 (F126L, K143R) and FKS1 (F621I and hotspot variants) are the primary drivers of the pronounced antifungal resistance observed in Chinese D. catenulata strains, with resistance phenotypes being modulated by nutrient availability.

The resistance mechanisms of Candida species can be summarized into three primary categories: (1) Mutations in Drug-Binding Targets; (2) Overexpression of Drug Targets; (3) Efflux of Antifungal Drugs.Infographic illustrating antifungal drug resistance mechanisms in fungi, featuring a plasma membrane with ergosterol, cell wall, beta-glucan synthase, drug efflux pumps, and mechanisms including target mutation, target overexpression, and drug efflux. Green panel shows drug sensitivity, red indicates resistance, with labeled azole and echinocandin interactions.

The resistance mechanisms of Candida species can be summarized into three primary categories: (1) Mutations in Drug-Binding Targets; (2) Overexpression of Drug Targets; (3) Efflux of Antifungal Drugs.