Facultative sterol uptake in an ergosterol-deficient clinical isolate of Candida glabrata harboring a missense mutation in ERG11 and exhibiting cross-resistance to azoles and amphotericin B.
Antimicrob Agents Chemother
; 56(8): 4223-32, 2012 Aug.
Article
em En
| MEDLINE
| ID: mdl-22615281
ABSTRACT
We identified a clinical isolate of Candida glabrata (CG156) exhibiting flocculent growth and cross-resistance to fluconazole (FLC), voriconazole (VRC), and amphotericin B (AMB), with MICs of >256, >256, and 32 µg ml(-1), respectively. Sterol analysis using gas chromatography-mass spectrometry (GC-MS) revealed that CG156 was a sterol 14α-demethylase (Erg11p) mutant, wherein 14α-methylated intermediates (lanosterol was >80% of the total) were the only detectable sterols. ERG11 sequencing indicated that CG156 harbored a single-amino-acid substitution (G315D) which nullified the function of native Erg11p. In heterologous expression studies using a doxycycline-regulatable Saccharomyces cerevisiae erg11 strain, wild-type C. glabrata Erg11p fully complemented the function of S. cerevisiae sterol 14α-demethylase, restoring growth and ergosterol synthesis in recombinant yeast; mutated CG156 Erg11p did not. CG156 was culturable using sterol-free, glucose-containing yeast minimal medium ((glc)YM). However, when grown on sterol-supplemented (glc)YM (with ergosta 7,22-dienol, ergosterol, cholestanol, cholesterol, Δ(7)-cholestenol, or desmosterol), CG156 cultures exhibited shorter lag phases, reached higher cell densities, and showed alterations in cellular sterol composition. Unlike comparator isolates (harboring wild-type ERG11) that became less sensitive to FLC and VRC when cultured on sterol-supplemented (glc)YM, facultative sterol uptake by CG156 did not affect its azole-resistant phenotype. Conversely, CG156 grown using (glc)YM with ergosterol (or with ergosta 7,22-dienol) showed increased sensitivity to AMB; CG156 grown using (glc)YM with cholesterol (or with cholestanol) became more resistant (MICs of 2 and >64 µg AMB ml(-1), respectively). Our results provide insights into the consequences of sterol uptake and metabolism on growth and antifungal resistance in C. glabrata.
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Base de dados:
MEDLINE
Assunto principal:
Azóis
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Anfotericina B
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Mutação de Sentido Incorreto
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Farmacorresistência Fúngica Múltipla
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Candida glabrata
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Esterol 14-Desmetilase
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Antifúngicos
Limite:
Humans
Idioma:
En
Ano de publicação:
2012
Tipo de documento:
Article