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Updated: Apr 21, 2026
Whole Genome Sequencing of Candida glabrata for Detection of Markers of Antifungal Drug Resistance
Published on: December 28, 2017
Contribution of clinically derived mutations in ERG11 to azole resistance in Candida albicans
Stephanie A Flowers1, Brendan Colón2, Sarah G Whaley1
1Department of Clinical Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee, USA.
Abstract:
In Candida albicans, the ERG11 gene encodes lanosterol demethylase, the target of the azole antifungals. Mutations in ERG11 that result in an amino acid substitution alter the abilities of the azoles to bind to and inhibit Erg11, resulting in resistance. Although ERG11 mutations have been observed in clinical isolates, the specific contributions of individual ERG11 mutations to azole resistance in C. albicans have not been widely explored. We sequenced ERG11 in 63 fluconazole (FLC)-resistant clinical isolates. Fifty-five isolates carried at least one mutation in ERG11, and we observed 26 distinct positions in which amino acid substitutions occurred. We mapped the 26 distinct variant positions in these alleles to four regions in the predicted structure for Erg11, including its predicted catalytic site, extended fungus-specific external loop, proximal surface, and proximal surface-to-heme region. In total, 31 distinct ERG11 alleles were recovered, with 10 ERG11 alleles containing a single amino acid substitution. We then characterized 19 distinct ERG11 alleles by introducing them into the wild-type azole-susceptible C. albicans SC5314 strain and testing them for susceptibilities to FLC, itraconazole (ITC), and voriconazole (VRC). The strains that were homozygous for the single amino acid substitutions Y132F, K143R, F145L, S405F, D446E, G448E, F449V, G450E, and G464S had a ≥ 4-fold increase in FLC MIC. The strains that were homozygous for several double amino acid substitutions had decreased azole susceptibilities beyond those conferred by any single amino acid substitution. These findings indicate that mutations in ERG11 are prevalent among azole-resistant clinical isolates and that most mutations result in appreciable changes in FLC and VRC susceptibilities.
Insights
Mutations in the ERG11 gene are common in azole-resistant Candida albicans. These ERG11 mutations significantly impact antifungal drug susceptibility, particularly to fluconazole and voriconazole.
Area of Science:
- Medical Mycology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Azole antifungals are crucial for treating Candida albicans infections.
- Resistance to azole antifungals is often mediated by mutations in the ERG11 gene, which encodes lanosterol demethylase.
- The specific impact of individual ERG11 mutations on azole resistance in clinical isolates remains incompletely understood.
Purpose of the Study:
- To investigate the prevalence and impact of ERG11 gene mutations in fluconazole-resistant clinical isolates of Candida albicans.
- To characterize the functional consequences of specific ERG11 mutations on susceptibility to multiple azole antifungal drugs.
Main Methods:
- Sequencing of the ERG11 gene in 63 fluconazole-resistant clinical isolates.
- Mapping of identified ERG11 variant positions to functional regions of the Erg11 protein.
- Introduction of characterized ERG11 alleles into a wild-type azole-susceptible Candida albicans strain.
- Phenotypic characterization of engineered strains for susceptibility to fluconazole, itraconazole, and voriconazole.
Main Results:
- Fifty-five of 63 resistant isolates harbored at least one ERG11 mutation, with 26 distinct amino acid substitution positions identified.
- Mutations were mapped to critical regions of the Erg11 protein, including the catalytic site.
- Homozygosity for single amino acid substitutions like Y132F and K143R conferred a ≥ 4-fold increase in fluconazole minimum inhibitory concentration (MIC).
- Certain double amino acid substitutions resulted in even greater reductions in azole susceptibility.
- Most characterized ERG11 mutations led to significant changes in susceptibility to fluconazole and voriconazole.
Conclusions:
- Mutations in the ERG11 gene are highly prevalent in azole-resistant clinical isolates of Candida albicans.
- Individual ERG11 mutations can significantly alter susceptibility to key azole antifungal drugs, contributing to treatment failure.
- These findings highlight the importance of ERG11 genotyping for understanding and managing azole resistance in Candida albicans infections.
