Flucytosine primary resistance in Candida species and Cryptococcus neoformans

The in vitro activity of flucytosine (5FC) against 1,140 clinical isolates of Candida spp. and Cryptococcus neoformans was evaluated and compared with the activity of amphotericin B, fluconazole and itraconatole. Overall, 87. 72% (1,000/1,140) of yeasts were susceptible to 5FC. This agent showed less potent in vitro activity against Candida glabrata, Candida krusei, Candida guillfermondii and Cryptococcus neoformans (MIC90s, 8-16 mug/ml) and inter mediate activity or resistance to 6.5% of Candida albicans, 5.1% of Candida tropicalis and 0.8% of Candida parapsilosis strains. Amphotericin B showed potent activity against isolates with an MIC of 5FC greater than or equal to 8 mug/ml. A total of 112 of 140 strains that were 5FC-intermediate or -r esistant showed decreased susceptibility to azoles (P < 0.01).