Fluconazole tolerance in clinical isolates of Cryptococcus neoformans

Kanamarlapudi, Venkateswarlu; Taylor, Mark B.; Manning, N. J.; Rinaldi, Michael G.; Kelly, Steven L.

doi:10.1128/aac.41.4.748

Cited by 68 publications

(38 citation statements)

References 24 publications

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“…In S. cerevisiae ERG5 has been reported to bind to azole drugs by a similar mechanism as ERG11 and we observed increased expression of C. neoformans ERG5 (CNAG_06644) as well. Sterol analysis of the flucanazole resistant C. albicans showed defects in ERG2 and ERG3 [51]. Homologs of S. cerevisiae ERG2 (CNAG_00854) and ERG3 (CNAG_00519) showed altered expression levels in our microarray dataset (Figure S2).…”

Section: Resultsmentioning

confidence: 84%

Global Transcriptome Profile of Cryptococcus neoformans during Exposure to Hydrogen Peroxide Induced Oxidative Stress

et al. 2013

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The ability of the opportunistic fungal pathogen Cryptococcus neoformans to resist oxidative stress is one of its most important virulence related traits. To cope with the deleterious effect of cellular damage caused by the oxidative burst inside the macrophages, C. neoformans has developed multilayered redundant molecular responses to neutralize the stress, to repair the damage and to eventually grow inside the hostile environment of the phagosome. We used microarray analysis of cells treated with hydrogen peroxide (H2O2) at multiple time points in a nutrient defined medium to identify a transcriptional signature associated with oxidative stress. We discovered that the composition of the medium in which fungal cells were grown and treated had a profound effect on their capacity to degrade exogenous H2O2. We determined the kinetics of H2O2 breakdown by growing yeast cells under different conditions and accordingly selected an appropriate media composition and range of time points for isolating RNA for hybridization. Microarray analysis revealed a robust transient transcriptional response and the intensity of the global response was consistent with the kinetics of H2O2 breakdown by treated cells. Gene ontology analysis of differentially expressed genes related to oxidation-reduction, metabolic process and protein catabolic processes identified potential roles of mitochondrial function and protein ubiquitination in oxidative stress resistance. Interestingly, the metabolic pathway adaptation of C. neoformans to H2O2 treatment was remarkably distinct from the response of other fungal organisms to oxidative stress. We also identified the induction of an antifungal drug resistance response upon the treatment of C. neoformans with H2O2. These results highlight the complexity of the oxidative stress response and offer possible new avenues for improving our understanding of mechanisms of oxidative stress resistance in C. neoformans.

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Section: Resultsmentioning

confidence: 84%

Global Transcriptome Profile of Cryptococcus neoformans during Exposure to Hydrogen Peroxide Induced Oxidative Stress

et al. 2013

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“…However, FLC-treated mice infected with C. albicans show morphologically changed yeast cells that likely stem from an inability to undergo cytokinesis (11). Isolates of C. neoformans obtained from clinical samples exhibited significant variation in susceptibility to FLC, and resistant clones with chromosomal disomy have been detected in brains of mice treated with FLC (28, 29). Thus, our in vitro data suggest that during infection with C. neoformans , treatment with FLC may lead to an increase in DNA content in yeast cells through pleiotropic effects on cell division.…”

Section: Discussionmentioning

confidence: 99%

Fluconazole-Induced Ploidy Change in Cryptococcus neoformans Results from the Uncoupling of Cell Growth and Nuclear Division

Altamirano

Fang

Simmons

et al. 2017

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Azoles are antifungals that are widely utilized due to relatively low toxicity and cost of treatment. One of their drawbacks, however, is that azoles are primarily cytostatic, leaving fungal cells capable of developing drug resistance. The human pathogen Cryptococcus neoformans acquires resistance to the azole drug fluconazole (FLC) through the development of aneuploidy, leading to elevated expression of key resistance genes, a mechanism that is also common for Candida albicans (K. J. Kwon-Chung and Y. C. Chang, PLoS Pathog 8:e1003022, 2012, https://doi.org/10.1371/journal.ppat.1003022; J. Morschhäuser, J Microbiol 54:192–201, 2016, https://doi.org/10.1007/s12275-016-5628-4). However, the exact ways in which FLC contributes to increased resistance in either of these important fungal pathogens remain unclear. Here we found that FLC treatment leads to an increase in DNA content in C. neoformans through multiple mechanisms, potentially increasing the size of a pool of cells from which aneuploids with increased resistance are selected. This study demonstrated the importance of FLC’s inhibitory effects on growth and cytokinesis in the generation of cell populations with decreased sensitivity to the drug.

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“…In these fungi, resistance is known to emerge via (1) increased production of multidrug transporters [14]–[16], (2) mutations in ergosterol biosynthetic pathway genes [17],[18], (3) amplification of genomic regions that contain ergosterol biosynthetic pathway genes and transcription factors that positively regulate a subsets of efflux pump genes [19],[20] and (4) activation of Hsp90 that may facilitate the cells to respond to drug stress [21],[22]. In C. neoformans , FLC resistant strains have rarely been reported and the emergence of resistance has most often been documented with clinical outcomes of AIDS patients receiving azole maintenance therapy [23]–[27]. The mechanism of resistance in C. neoformans during maintenance therapy is poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Cryptococcus neoformans Overcomes Stress of Azole Drugs by Formation of Disomy in Specific Multiple Chromosomes

et al. 2010

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Cryptococcus neoformans is a haploid environmental organism and the major cause of fungal meningoencephalitis in AIDS patients. Fluconazole (FLC), a triazole, is widely used for the maintenance therapy of cryptococcosis. Heteroresistance to FLC, an adaptive mode of azole resistance, was associated with FLC therapy failure cases but the mechanism underlying the resistance was unknown. We used comparative genome hybridization and quantitative real-time PCR in order to show that C. neoformans adapts to high concentrations of FLC by duplication of multiple chromosomes. Formation of disomic chromosomes in response to FLC stress was observed in both serotype A and D strains. Strains that adapted to FLC concentrations higher than their minimal inhibitory concentration (MIC) contained disomies of chromosome 1 and stepwise exposure to even higher drug concentrations induced additional duplications of several other specific chromosomes. The number of disomic chromosomes in each resistant strain directly correlated with the concentration of FLC tolerated by each strain. Upon removal of the drug pressure, strains that had adapted to high concentrations of FLC returned to their original level of susceptibility by initially losing the extra copy of chromosome 1 followed by loss of the extra copies of the remaining disomic chromosomes. The duplication of chromosome 1 was closely associated with two of its resident genes: ERG11, the target of FLC and AFR1, the major transporter of azoles in C. neoformans. This adaptive mechanism in C. neoformans may play an important role in FLC therapy failure of cryptococcosis leading to relapse during azole maintenance therapy.

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Fluconazole tolerance in clinical isolates of Cryptococcus neoformans

Cited by 68 publications

References 24 publications

Global Transcriptome Profile of Cryptococcus neoformans during Exposure to Hydrogen Peroxide Induced Oxidative Stress

Global Transcriptome Profile of Cryptococcus neoformans during Exposure to Hydrogen Peroxide Induced Oxidative Stress

Fluconazole-Induced Ploidy Change in Cryptococcus neoformans Results from the Uncoupling of Cell Growth and Nuclear Division

Cryptococcus neoformans Overcomes Stress of Azole Drugs by Formation of Disomy in Specific Multiple Chromosomes

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