TY - JOUR
T1 - Loss of C-5 sterol desaturase activity results in increased resistance to azole and echinocandin antifungals in a clinical isolate of candida parapsilosis
AU - Rybak, Jeffrey M.
AU - Dickens, C. Michael
AU - Parker, Josie E.
AU - Caudle, Kelly E.
AU - Manigaba, Kayihura
AU - Whaley, Sarah G.
AU - Nishimoto, Andrew T.
AU - Luna-Tapia, Arturo
AU - Roy, Sujoy
AU - Zhang, Qing
AU - Barker, Katherine S.
AU - Palmer, Glen E.
AU - Sutter, Thomas R.
AU - Homayouni, Ramin
AU - Wiederhold, Nathan P.
AU - Kelly, Steven L.
AU - Rogers, P. David
N1 - Funding Information:
The research contained in this report was supported by National Institutes of Health (NIH) grant R01 AI058145 (to P.D.R.). Partial support for DNA sequencing and analysis was provided by the Memphis Research Consortium (to T.R.S.).
Funding Information:
We thank Elizabeth L. Berkow for her contributions to the construction of the C. parapsilosis ERG3 mutants used in this study, Joachim Morschh?user for his invaluable expertise and for generously providing the pSFS2 plasmid used in the gene disruption and complementation experiments, and Shirlean Goodwin for her assistance with the improvement of genomic DNA isolation and sequencing methods. The research contained in this report was supported by National Institutes of Health (NIH) grant R01 AI058145 (to P.D.R.). Partial support for DNA sequencing and analysis was provided by the Memphis Research Consortium (to T.R.S.).
Publisher Copyright:
Copyright © 2017 American Society for Microbiology. All Rights Reserved.
PY - 2017/9
Y1 - 2017/9
N2 - Among emerging non-albicans Candida species, Candida parapsilosis is of particular concern as a cause of nosocomial bloodstream infections in neonatal and intensive care unit patients. While fluconazole and echinocandins are considered effective treatments for such infections, recent reports of fluconazole and echinocandin resistance in C. parapsilosis indicate a growing problem. The present study describes a novel mechanism of antifungal resistance in this organism affecting susceptibility to azole and echinocandin antifungals in a clinical isolate obtained from a patient with prosthetic valve endocarditis. Transcriptome analysis indicated differential expression of several genes in the resistant isolate, including upregulation of ergosterol biosynthesis pathway genes ERG2, ERG5, ERG6, ERG11, ERG24, ERG25, and UPC2. Whole-genome sequencing revealed that the resistant isolate possessed an ERG3 mutation resulting in a G111R amino acid substitution. Sterol profiles indicated a reduction in sterol desaturase activity as a result of this mutation. Replacement of both mutant alleles in the resistant isolate with the susceptible isolate’s allele restored wild-type susceptibility to all azoles and echinocandins tested. Disruption of ERG3 in the susceptible and resistant isolates resulted in a loss of sterol desaturase activity, high-level azole resistance, and an echinocandin-intermediate to -resistant phenotype. While disruption of ERG3 in C. albicans resulted in azole resistance, echinocandin MICs, while elevated, remained within the susceptible range. This work demonstrates that the G111R substitution in Erg3 is wholly responsible for the altered azole and echinocandin susceptibilities observed in this C. parapsilosis isolate and is the first report of an ERG3 mutation influencing susceptibility to the echinocandins.
AB - Among emerging non-albicans Candida species, Candida parapsilosis is of particular concern as a cause of nosocomial bloodstream infections in neonatal and intensive care unit patients. While fluconazole and echinocandins are considered effective treatments for such infections, recent reports of fluconazole and echinocandin resistance in C. parapsilosis indicate a growing problem. The present study describes a novel mechanism of antifungal resistance in this organism affecting susceptibility to azole and echinocandin antifungals in a clinical isolate obtained from a patient with prosthetic valve endocarditis. Transcriptome analysis indicated differential expression of several genes in the resistant isolate, including upregulation of ergosterol biosynthesis pathway genes ERG2, ERG5, ERG6, ERG11, ERG24, ERG25, and UPC2. Whole-genome sequencing revealed that the resistant isolate possessed an ERG3 mutation resulting in a G111R amino acid substitution. Sterol profiles indicated a reduction in sterol desaturase activity as a result of this mutation. Replacement of both mutant alleles in the resistant isolate with the susceptible isolate’s allele restored wild-type susceptibility to all azoles and echinocandins tested. Disruption of ERG3 in the susceptible and resistant isolates resulted in a loss of sterol desaturase activity, high-level azole resistance, and an echinocandin-intermediate to -resistant phenotype. While disruption of ERG3 in C. albicans resulted in azole resistance, echinocandin MICs, while elevated, remained within the susceptible range. This work demonstrates that the G111R substitution in Erg3 is wholly responsible for the altered azole and echinocandin susceptibilities observed in this C. parapsilosis isolate and is the first report of an ERG3 mutation influencing susceptibility to the echinocandins.
KW - Antifungal resistance
KW - Antimicrobial activity
KW - Antimicrobial agents
KW - Candida
KW - Ergosterol
KW - Molecular genetics
KW - Mycology
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UR - http://www.scopus.com/inward/citedby.url?scp=85028368825&partnerID=8YFLogxK
U2 - 10.1074/jbc.M117.794248
DO - 10.1074/jbc.M117.794248
M3 - Article
C2 - 28630186
AN - SCOPUS:85028368825
SN - 0066-4804
VL - 61
JO - Antimicrobial agents and chemotherapy
JF - Antimicrobial agents and chemotherapy
IS - 9
M1 - e00651-17
ER -