Systematic truncations of chromosome 4 and their responses to antifungals in Candida albicans

Abstract

Background Candida albicans is an opportunistic human fungal pathogen responsible for superficial and systemic life-threatening infections. Treating these infections is challenging as many clinical isolates show increased drug resistance to antifungals. Chromosome (Chr) 4 monosomy was implicated in a fluconazole-resistant mutant. However, exposure to fluconazole adversely affects Candida cells and can generate numerous mutations. Hence, the present study aimed to truncate Chr4 and challenge the generated Candida strains to antifungals and evaluate their role in drug response. Results Herein, Chr4 was truncated in C. albicans using the telomere-mediated chromosomal truncation method. The resulting eight Candida strains carrying one truncated homolog of Chr4 were tested for response to multiple antifungals. The minimal inhibitory concentration (MIC) for these strains was determined against three classes of antifungals. The MIC values against fluconazole, amphotericin B, and caspofungin were closer to that of the wild type strain. Microdilution assay against fluconazole showed that the mutants and wild type strains had similar sensitivity to fluconazole. The disc diffusion assay against five azoles and two polyenes revealed that the zones of inhibition for all the eight strains were similar to those of the wild type. Thus, none of the generated strains showed any significant resistance to the tested antifungals. However, spot assay exhibited a reasonably high tolerance of a few generated strains with increasing concentrations of fluconazole. Conclusion This analysis suggested that Chr4 aneuploidy might not underlie drug resistance but rather drug tolerance in Candida albicans.

Molecular Diagnostics for Invasive Fungal Diseases: Current and Future Approaches

“…Keighley et al described breakthrough C. albicans bloodstream infection following in vivo development of a 14-bp deletion in the ERG3 gene, resulting in pan-azole resistance. Genomic analysis of antifungal drug resistance remains complex, as novel mechanisms play a significant role, such as promoters introduced by transposable elements [173], or chromosomal monosomy [174].…”

The challenges of the genome-based identification of antifungal resistance in the clinical routine

“…Large changes include ploidy alterations, the combination of chromosomes into new ones, and the generation of isochromosomes ( Selmecki et al, 2006 , 2008 ; McTaggart et al, 2020 ). For example, chromosomal monosomies have been associated with tolerance to fluconazole and 5-flourocytosine ( Yang et al, 2013 ; Uddin et al, 2021 ). The copy number of genes coding primary targets can be also increased by local duplication ( Chow et al, 2020 ).…”