In-vitro susceptibilities of voriconazole against Korean clinical Aspergillus isolates

Background: Voriconazole is a potent new triazole antifungal agent expected to be particularly useful for the treatment of invasive aspergillosis. However, in vitro susceptibility of voriconazole for clinical strains of Aspergillus species isolated in Korea has not been fully surveyed. Objective: We determined minimum inhibitory concentrations (MICs) of voriconazole for clinical Aspergillus isolates. Methods: A total of 100 clinical isolates of Aspergillus species (40 A. fumigatus, 24 A. flavus, 17 A. niger, 17 A. terreus and 2 A. nidulans) was tested. In vitro voriconazole susceptibility testing was accomplished utilizing the National Committee for Clinical Laboratory Standards (NCCLS) broth microdilution method M38-A. MIC of voriconazole was determined using RPMI medium at 48 h of incubation. Results: Among the 100 isolates of Aspergillus species tested, 98% were inhibited by ≤ 1 μg/mL of voriconazole. The MICs of voriconazole ranged from 0.125 to 2 μg/mL (geometric mean MIC, 0.52 μg/mL). The MIC₅₀ (MIC at which 50% of the isolates tested were inhibited) and MIC₉₀ were 0.5 and 1.0 μg/mL for all Aspergillus species, respectively. The strains showing MIC≥2 μg/mL were 0/40 (0%) in A. fumigatus, 1/24 (4%) in A. flavus, 1/1.7 (6%) in A. niger, 0/17 (0%) in A. terreus, and 0/2 (0%) in A. nidulans. Conclusion: These data demonstrate promising in-vitro activity of voriconazole against clinical strains of Aspergillus species isolated from Korean patients.