In vitro activities of polyene and imidazole antifungal agents against unusual opportunistic fungal pathogens.

Guidelines for the treatment of infections caused by unusual opportunistic fungi are limited and available in vitro data are scanty. In vitro susceptibility tests, employing an agar dilution procedure, were performed with amphotericin B (AMB), natamycin (NTC), itraconazole (ICZ), and ketoconazole (KTZ). Two media were used: Kimmig's agar (KA) and Yeast Morphology Agar (YMA). Fungi tested included isolates (n) of Acremonium spp. (10), Cunninghamella spp. (6), Fusarium spp. (18), Pseudallescheria boydii (14), and Trichosporon beigelii (5). All Acremonium and Cunninghamella isolates were susceptible to NTC (MIC less than or equal to 4 micrograms/ml) but many appeared to be resistant to AMB, (MIC greater than or equal to 32 micrograms/ml), KTZ and ICZ (MIC greater than or equal to 128 micrograms/ml). Most isolates of Fusarium spp. were susceptible to both AMB and NTC (MIC90 = 4 micrograms/ml); one isolate was cross-resistant to both polyenes (MIC greater than 32 micrograms/ml). Only two of 18 Fusarium isolates appeared susceptible to the imidazoles (MIC less than or equal to 4 micrograms/ml); the remaining isolates exhibited high MICs (greater than or equal to 64 micrograms/ml). All 14 isolates of P. boydii were susceptible to NTC (MIC less than or equal to 4 micrograms/ml) but four appeared to be resistant to AMB (MIC greater than or equal to 32 micrograms/ml). Most isolates of P. boydii were susceptible to both KTZ (MIC less than or equal to 4 micrograms/ml) and ICZ (MIC less than or equal to 16 micrograms/ml) but two isolates appeared to be resistant (MIC greater than or equal to 16 micrograms/ml).(ABSTRACT TRUNCATED AT 250 WORDS)