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Updated: Jun 25, 2025
Whole Genome Sequencing of Candida glabrata for Detection of Markers of Antifungal Drug Resistance
Published on: December 28, 2017
Sequential Induction of Drug Resistance and Characterization of an Initial Candida albicans Drug-Sensitive Isolate
Setrida El Hachem1, Nour Fattouh1,2, Christy Chedraoui1
1Department of Natural Sciences, Lebanese American University, Byblos P.O. Box 36, Lebanon.
Background:
The pathogenic fungus Candida albicans is a leading agent of death in immunocompromised individuals with a growing trend of antifungal resistance.
Methods:
The purpose is to induce resistance to drugs in a sensitive C. albicans strain followed by whole-genome sequencing to determine mechanisms of resistance. Strains will be assayed for pathogenicity attributes such as ergosterol and chitin content, growth rate, virulence, and biofilm formation.
Results:
We observed sequential increases in ergosterol and chitin content in fluconazole-resistant isolates by 78% and 44%. Surface thickening prevents the entry of the drug, resulting in resistance. Resistance imposed a fitness trade-off that led to reduced growth rates, biofilm formation, and virulence in our isolates. Sequencing revealed mutations in genes involved in resistance and pathogenicity such as ERG11, CHS3, GSC2, CDR2, CRZ2, and MSH2. We observed an increase in the number of mutations in key genes with a sequential increase in drug-selective pressures as the organism increased its odds of adapting to inhospitable environments. In ALS4, we observed two mutations in the susceptible strain and five mutations in the resistant strain.
Conclusion:
This is the first study to induce resistance followed by genotypic and phenotypic analysis of isolates to determine mechanisms of drug resistance.
Insights
This study induced drug resistance in Candida albicans, revealing increased cell wall components and genetic mutations. This resistance led to reduced virulence, offering insights into antifungal drug mechanisms.
Area of Science:
- Medical Mycology
- Antimicrobial Resistance
- Genomics
Background:
- Candida albicans is a major cause of mortality in immunocompromised patients.
- Antifungal resistance in C. albicans is an increasing global health concern.
Purpose of the Study:
- To induce drug resistance in a susceptible C. albicans strain.
- To identify the genetic and phenotypic mechanisms underlying acquired antifungal resistance.
- To investigate the impact of resistance on fungal pathogenicity attributes.
Main Methods:
- Induction of drug resistance in C. albicans.
- Whole-genome sequencing to identify mutations.
- Assays for ergosterol and chitin content, growth rate, virulence, and biofilm formation.
Main Results:
- Fluconazole-resistant isolates showed increased ergosterol (78%) and chitin (44%), linked to cell surface thickening.
- Acquired resistance resulted in reduced growth rates, biofilm formation, and virulence.
- Genomic analysis revealed mutations in key genes (e.g., ERG11, CHS3, CDR2, CRZ2, MSH2, ALS4) associated with resistance and pathogenicity.
Conclusions:
- This study provides the first combined genotypic and phenotypic analysis of induced drug resistance in C. albicans.
- Understanding these resistance mechanisms is crucial for developing new antifungal therapies.
