Acquisition of cross-azole tolerance and aneuploidy inCandida albicansstrains evolved to posaconazole

Abstract

A number of in vitro studies have examined the acquisition of drug resistance to the triazole fluconazole, a first-line treatment for many Candida infections. Much less is known about posaconazole, a newer triazole. We conducted the first in vitro experimental evolution of replicates from eight diverse strains of C. albicans in a high level of the fungistatic drug posaconazole. Approximately half of the 132 evolved replicates survived 50 generations of evolution, biased towards some of the strain backgrounds. We found that although increases in drug resistance were rare, increases in drug tolerance (the slow growth of a subpopulation of cells in a level of drug above the resistance level) were common across strains. We also found that adaptation to posaconazole resulted in widespread cross-tolerance to other azole drugs. Widespread aneuploidy variation was also observed in evolved replicates from some strain backgrounds. Trisomy of chromosomes 3, 6, and R was identified in 11 of 12 whole-genome sequenced evolved SC5314 replicates. These findings document rampant evolved cross-tolerance among triazoles and highlight that increases in drug tolerance can evolve independently of drug resistance in a diversity of C. albicans strain backgrounds.

Experimental and in-host evolution of triazole resistance in human pathogenic fungi

“…Similarities between Candida spp. and C. neoformans can be found in aneuploidy and CNVs mechanisms, found in both approaches in both yeasts ( Mondon et al., 1999 ; Coste et al., 2007 ; Selmecki et al., 2008 ; Sionov et al., 2010 ; Huang et al., 2011 ; Ormerod et al., 2013 ; Chen et al., 2017 ; Stone et al., 2019 ; Todd et al., 2019 ; Todd and Selmecki, 2020 ; Carolus et al., 2021 ; Kukurudz et al., 2022 ). Aneuploidies have not been reported in A. fumigatus.…”

“…In general, resistance mechanisms identified by experimental evolution match the results seen in serial clinical isolates. For example, in all three organisms reviewed here, key shared drivers of resistance are the overexpression of ERG11/cyp51A, encoding the target enzyme of triazoles, and of efflux transporters from the ABC (CDR1/2 in Candida spp., AFR1 in Cryptococcus spp., (Mondon et al, 1999;Coste et al, 2007;Selmecki et al, 2008;Sionov et al, 2010;Huang et al, 2011;Ormerod et al, 2013;Chen et al, 2017;Stone et al, 2019;Todd et al, 2019;Todd and Selmecki, 2020;Carolus et al, 2021;Kukurudz et al, 2022). Aneuploidies have not been reported in A. fumigatus.…”

“…In addition, changes in expression (either induction or repression of expression) were observed in ERG1 , ERG3 , and ERG13 ( Silva et al., 2016 ). ChrR (chromosome R, encoding rDNA genes) changes have also been frequently described ( Cowen et al., 2000 ; Huang et al., 2011 ; Kukurudz et al., 2022 ), along with Chr3 (containing CDR1 and CDR2 ), as well as Chr4 and Chr6 aneuploidies, where the resistance mechanism remains unclear ( Huang et al., 2011 ; Todd et al., 2019 ; Todd and Selmecki, 2020 ; Kukurudz et al., 2022 ). Overexpression and CNVs of genes involved in membrane and cell wall integrity ( YPL88 , YPX98 , PDR16 , CRZ1 , CDR3 , NCP1 , ECM21 , MNN23 , RHB1 , and KRE6 ), stress response ( HYR1 , GRE99 , YNL229C , HSP70 , CGR1 , ERO1 , TPK1 , ASR1 , and PBS2 ) have also been reported, none of which have been proven to cause triazole resistance ( Table 3 ) ( Cowen et al., 2002 ; Todd and Selmecki, 2020 ).…”

“…Compared with the clinical isolate studies described above, the laboratory evolutionary studies find less gain-of-function mutations in TAC1 and UPC2, with less isochromosome formation and more aneuploidies of chromosomes other than Chr5 (Huang et al, 2011;Todd et al, 2019;Todd and Selmecki, 2020;Kukurudz et al, 2022). In addition, in-vitro evolution studies more frequently describe the overexpression or CNVs of genes outside the ergosterol-biosynthesis pathway (Silva et al, 2016;Todd and Selmecki, 2020).…”