A comparativein vitrostudy of amphotericin B, clotrimazole and 5-fluorocytosine against clinically isolated yeasts

Minimum inhibitory concentrations of amphotericin B, clotrimazole and 5-fluorocytosine have been determined against 413 yeast strains isolated from clinical material. All 343 strains of Candida albicans were inhibited by 4 μg/ml of amphotericin B and by 16 μg/ml of clotrimazole, while 40 (11·7%) were resistant (MIC≥ 50 μg/ml) to 5-fluorocytosine. The 53 strains of Torulopsis glabrata were more sensitive to amphotericin B and less sensitive to clotrimazole than were the C. albicans strains, and 14 (24%) were resistant to 5-fluorocytosine. At concentrations of the drugs attainable in vivo (2–3, 3 and 100 μg/ml respectively), 83·4%, 16·7% and 89% of all the strains isolated would be inhibited by amphotericin B, clotrimazole and 5-fluorocytosine. From these in vitro results, it is possible that 5-fluorocytosine may show greater activity in vivo than clotrimazole against yeasts responsible for candidiasis in humans.