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Updated: Sep 8, 2025
Whole Genome Sequencing of Candida glabrata for Detection of Markers of Antifungal Drug Resistance
Published on: December 28, 2017
Mutations in TAC1B drive increased CDR1 and MDR1 expression and azole resistance in Candida auris
Katherine S Barker1, Darian J Santana1, Qing Zhang1
1Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
Abstract:
Candida auris has emerged as a fungal pathogen of particular concern owing in part to its propensity to exhibit antifungal resistance, especially to the commonly prescribed antifungal fluconazole. A mutation in TAC1B, which encodes a zinc cluster transcription factor, has been shown to confer increased resistance to fluconazole. In this work, we aimed to determine how mutations in TAC1B exert this effect. TAC1B mutations leading to A640V, A657V, and F862_N866del, found in fluconazole-resistant clinical isolates, were introduced into two susceptible Clade I backgrounds using CRISPR-Cas9 gene editing. These TAC1B mutations conferred increased fluconazole resistance, as well as increased resistance to other triazoles as measured by broth microdilution. RNA-seq revealed that the ATP-binding cassette (ABC) transporter gene CDR1 as well as the major facilitator superfamily (MFS) transporter gene MDR1 were both upregulated in the presence of these TAC1B mutations. Disruption of CDR1 increased susceptibility in strains with TAC1B mutations, whereas disruption of MDR1 had little to no effect. However, disruption of both CDR1 and MDR1 resulted in an additional increase in susceptibility as compared with disruption of CDR1 alone. TAC1B mutations, leading to A640V, A657V, and F862_N866del all result in increased resistance to fluconazole and other triazole antifungals and increased expression of both CDR1 and MDR1 in C. auris. Together, these data suggest CDR1 is the primary driver of resistance conferred by these TAC1B mutations.
Insights
Mutations in TAC1B increase resistance to fluconazole in Candida auris by upregulating the CDR1 gene, a key transporter. This finding is crucial for understanding and combating antifungal drug resistance.
Area of Science:
- Mycology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Candida auris is a significant fungal pathogen known for antifungal resistance, particularly to fluconazole.
- Specific mutations in TAC1B have been linked to increased fluconazole resistance.
Purpose of the Study:
- To elucidate the mechanism by which TAC1B mutations confer fluconazole resistance in Candida auris.
- To investigate the role of ABC and MFS transporter genes in this resistance mechanism.
Main Methods:
- CRISPR-Cas9 gene editing was used to introduce specific TAC1B mutations (A640V, A657V, F862_N866del) into susceptible Candida auris strains.
- Broth microdilution assays measured antifungal resistance.
- RNA-sequencing (RNA-seq) analyzed gene expression changes, focusing on transporter genes.
- Gene disruption experiments assessed the impact of CDR1 and MDR1 on fluconazole susceptibility.
Main Results:
- Introduced TAC1B mutations conferred increased resistance to fluconazole and other triazoles.
- RNA-seq revealed upregulation of both CDR1 (ATP-binding cassette transporter) and MDR1 (major facilitator superfamily transporter) genes.
- Disruption of CDR1 increased susceptibility, while MDR1 disruption had minimal effect.
- Disrupting both CDR1 and MDR1 led to greater susceptibility than disrupting CDR1 alone.
- TAC1B mutations enhance expression of CDR1 and MDR1.
Conclusions:
- TAC1B mutations confer fluconazole and triazole resistance in Candida auris.
- The CDR1 gene is identified as the primary mediator of this resistance.
- Understanding this mechanism is vital for developing strategies against resistant Candida auris infections.
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