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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. / CM Hull; JE Parker; O Bader; M Weig; U Gross; Warrilow AGS; DE Kelly; Steven Kelly

Antimicrob Agents Chemother. 2012 Aug;56(8):4223-32. May 21. [Epub ahead of print], Volume: 56, Pages: 4223 - 4232

Swansea University Author: Steven, Kelly

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); MICs of >256, >256 and 32 μg ml(-1), respectively. Sterol analysis using gas chromatography-mass spectrometry (GC-MS...

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Published in: Antimicrob Agents Chemother. 2012 Aug;56(8):4223-32. May 21. [Epub ahead of print]
Published: American Society of Microbiology 2012
URI: https://cronfa.swan.ac.uk/Record/cronfa11722
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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); 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 > 80% of 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 Yeast Minimal media ((glc)YM). However, when grown on sterol-supplemented (glc)YM (+ 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 + ergosterol (or + ergosta 7,22-dienol) showed increased sensitivity to AMB; CG156 grown using (glc)YM + cholesterol (or + cholestanol) became more resistant (MICs of 2 and > 64 μg AMB ml(-1), respectively). Results provide insights into the consequences of sterol uptake and metabolism on growth and antifungal resistance in C. glabrata.
College: Swansea University Medical School
Start Page: 4223
End Page: 4232