Variables influencing susceptibility testing of Cryptococcus neoformans to 5-fluorocytosine.
The minimum inhibitory concentration (MIC) of 5-fluorocytosine (5-FC) was determined for 65 isolates of Cryptococcus neoformans by using a twofold serial tube dilution method. The MIC was profoundly influenced by incubation temperature, inoculum size, and duration of incubation. By using a standard set of test conditions, 100% of 49 pretreatment isolates of C. neoformans were susceptible to 10 mug of 5-FC per ml or less, and 9 (56%) of 16 isolates recovered during or after 5-FC therapy were massively drug resistant (MIC > 320 mug/ml). With the standard test conditions recommended here, the tube dilution method was found to be both accurate and reproducible, and the results correlated with the treatment status of patients.
D000935:Antifungal Agents; D003454:Cryptococcus / Q000187:drug effects*; D003455:Cryptococcus neoformans / Q000187:drug effects; D003596:Cytosine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005437:Flucytosine / Q000494:pharmacology; D008826:Microbial Sensitivity Tests
D000935:Antifungal Agents; D003596:Cytosine; D005437:Flucytosine