Defined Anaerobic Growth Medium for Studying Candida albicans Basic Biology and Resistance to Eight Antifungal Drugs

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Abstract
The polymorphic fungus Candida albicans is one of the most versatile opportunistic pathogens in humans. Many organs of the human body are potential targets for infection by this pathogen, but infection is commonly localized in the gastrointestinal tract, an environment providing anaerobic growth conditions. We describe a chemically defined anaerobic growth medium for four strains of Candida albicans (A72, SC5314, MEN, and 10261). It is a defined liquid glucose-phosphate-proline growth medium supplemented with oleic acid, nicotinic acid, and ammonium chloride. The cells did not require or respond to added ergosterol. Oleic acid and nicotinic acid are growth factors which are required only for the anaerobic growth of C. albicans. An important technical feature of this study was the use of anaerobically grown inocula to study anaerobic growth. Anaerobically, the cells grew exclusively as mycelia at 25, 30, and 37°C. The doubling time at 30°C was ca. 20 h. The cells did not produce farnesol and did not respond to exogenous farnesol, and they were resistant to the highest tested levels of amphotericin B and four of the azole antifungals. We suggest that the anaerobic growth of C. albicans may contribute to the trailing end point phenomenon and the resistance of C. albicans biofilms to antifungal drugs.