Acetate-mediated growth inhibition in sterol 14alpha-demethylation-deficient cells of Candida albicans.
Candida albicans is a fungus thought to be viable in the presence of a deficiency in sterol 14alpha-demethylation. We showed in a strain of this species that the deficiency, caused either by a mutation or by an azole antifungal agent, made the cells susceptible to growth inhibition by acetate included in the culture medium. Studies with a mutant demonstrated that the inhibition was complete at a sodium acetate concentration of 0.24 M (20 g/liter) and was evident even at a pH of 8, the latter result indicating the involvement of acetate ions rather than the undissociated form of acetic acid. In fluconazole-treated cells, sterol profiles determined by thin-layer chromatography revealed that the minimum sterol 14alpha-demethylation-inhibitory concentrations (MDICs) of the drug, thought to be the most important parameter for clinical purposes, were practically identical in the media with and without 0.24 M acetate and were equivalent to the MIC in the acetate-supplemented medium. The acetate-mediated growth inhibition of azole-treated cells was confirmed with two additional strains of C. albicans and four different agents, suggesting the possibility of generalization. From these results, it was surmised that the acetate-containing medium may find use in azole susceptibility testing, for which there is currently no method capable of measuring MDICs directly for those fungi whose viability is not lost as a result of sterol 14alpha-demethylation deficiency. Additionally, the acetate-supplemented agar medium was found to be useful in detecting reversions from sterol 14alpha-demethylation deficiency to proficiency.
Shimokawa
O
O
Department of Microbiology, Faculty of Dentistry, Kyushu University, Higashi-ku, Fukuoka 812-8582, Japan.
Nakayama
H
H
D000085:Acetates / Q000494:pharmacology*; D001393:Azoles / Q000494:pharmacology; D002176:Candida albicans / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D002855:Chromatography, Thin Layer; D015169:Colony Count, Microbial; D003577:Cytochrome P-450 Enzyme System / Q000172:deficiency* / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D009154:Mutation; D010088:Oxidoreductases / Q000172:deficiency* / Q000235:genetics; D058886:Sterol 14-Demethylase; D013261:Sterols / Q000378:metabolism
D000085:Acetates; D001393:Azoles; D013261:Sterols; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase