In Vitro Activities of Polyene and Imidazole Antifungal Agents Against Unusual Opportunistic Fungal Pathogens

Publisher Website
Google Scholar
Abstract
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 A cremonium 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 ≤4 μg/ml) but many appeared to be resistant to AMB, (MIC ≧32 μg/m1), KTZ and ICZ (MIC ≧128 μg/ml). Most isolates of Fusarium spp. were susceptible to both AMB and NTC (MIC90 = 4 μg/ml); one isolate was cross-resistant to both polyenes (MIC > 32 μg/ml ). Only two of 18 Fusarium isolates appeared susceptible to the imidazoles (MIC ≤4 μg/ml); the remaining isolates exhibited high MICs (≧64 μg/ ml). All 14 isolates of P. boydii were susceptible to NTC (MIC ≤ μg/ml) but four appeared to be resistant to AMB (MIC 32 μg/ ml). Most isolates of P. boydii were susceptible to both KTZ (MIC ≤4 μg/ml) and ICZ (MIC ≤ 16 μg/ml) but two isolates appeared to be resistant (MIC ≧ 16 μg/ml). AMB was the most active compound against T. beigelii (MIC90 = 0.25 μg/ml) while KTZ was the least active (MIC90 = 64 μg/ml). Sixty-one MICs were determined for the four drugs on both KA and YMA. The best inter-test agreement (equal or ± 1 dilution) between paired KA and YMA MICs was observed in tests with NTC (93 %) while the poorest was observed in tests with ICZ (79 %). Four-fold or greater differences in paired MICs were observed in two tests each with AMB and ICZ.