Sequencing and Detection of Two Missense Variants at Chromosome 7 as Potential Azole Resistance Markers in Saccharomyces Cerevisiae

Abstract

Introduction: Widespread practices of over-prescribing antibiotic, antiviral, and antifungal drugs have sparked concern over the risk of antimicrobial resistance arising in bacterial, viral, and fungal pathogens. This risk threatens to jeopardize the efficacy of many drugs being prescribed today for said infections. Azoles are a major class of antifungal drugs, presenting the need for research efforts on mechanisms of azole resistance. My objective was to perform the genomic sequencing and variant profiling of a Baker’s Yeast (Saccharomyces cerevisiae) strain that displays resistance phenotype when plated with Clotrimazole, a type of azole antifungal. Methods: Through short-read genomic sequencing and subsequent variant calling, putative antifungal resistance genotypes were elucidated in a clotrimazole-resistant yeast strain. Results: Variant calls at the PDR1 and ERG25 loci reveal two potential Clotrimazole-resistance genotypes. Discussion: These variants are both missense mutations involving a single-nucleotide change to the reference genomic loci in question. Although PDR1 variants are putative markers of azole resistance in yeast, the emergence of a novel ERG25 variant that may contribute to this phenotype has not yet been. Conclusion: Follow-up experiments will need to include induced missense mutations at the ERG25 loci and selection assays to confirm that the described variants described here indeed constitute azole resistance. Establishing a knowledgebase of resistance marker genes and putative resistance variants for model organisms such as Saccharomyces cerevisiae can guide investigations into orthologous proteins in other species that may become responsible for future antifungal-resistant infections.