In Vitro Susceptibilities of Clinical Isolates of Aspergillus Species against Echinocandins

ABSTRACT

BACKGROUND: Echinocandins are a new class of antifungal agents with potent in vitro and in vivo activities against Aspergillus species. We investigated the in vitro activity of caspofungin and micafungin against Korean clinical Aspergillus isolates. MATERIALS AND METHODS: A total of 100 clinical isolates of Aspergillus species (32 A. fumigatus, 26 A. flavus, 22 A. niger and 20 A. terreus) were tested. The susceptibilities of caspofungin, micafungin, amphotericin B and itraconazole were established by means of the Clinical and Laboratory Standards Institute (CLSI) M38-A microdilution methods. The results for caspofungin and micafungin were evaluated by using the end points of minimum inhibitory concentrations (MIC) and minimum effective concentration (MEC, the lowest concentration that produces short and aberrant hyphal branchings microsopically). RESULTS: The MEC ranges of caspofungin and micafungin against 100 isolates of Aspergillus species were 0.06 to 0.5 microgram/mL and 16 microgram/mL unexpectedly, in 5% (5/100) and 4% (4/100) of isolates, respectively, which resulted in the loss of a consistent correlation between the two endpoint readings. The MEC50 of all Aspergillus isolates for caspofungin and micafungin were 0.25 and < or =0.03 /mL, respectively, and the MIC50 for amphotericin B and itraconazole were 0.5 and 0.25 microgram/mL, respectively. There were no species-related differences in caspofungin and micafungin MECs for Aspergillus species. CONCLUSION: This data demonstrates excellent in vitro activity of echinocandins against clinical strains of Aspergillus species.