International Evaluation of MIC Distributions and Epidemiological Cutoff Value (ECV) Definitions for Fusarium Species Identified by Molecular Methods for the CLSI Broth Microdilution Method
ABSTRACTThe CLSI epidemiological cutoff values (ECVs) of antifungal agents are available for variousCandidaspp.,Aspergillusspp., and the Mucorales. However, those categorical endpoints have not been established forFusariumspp., mostly due to the difficulties associated with collecting sufficient CLSI MICs for clinical isolates identified according to the currently recommended molecular DNA-PCR-based identification methodologies. CLSI MIC distributions were established for 53Fusarium dimerumspecies complex (SC), 10F. fujikuroi, 82F. proliferatum, 20F. incarnatum-F. equisetiSC, 226F. oxysporumSC, 608F. solaniSC, and 151F. verticillioidesisolates originating in 17 laboratories (in Argentina, Australia, Brazil, Canada, Europe, Mexico, and the United States). According to the CLSI guidelines for ECV setting, ECVs encompassing ≥97.5% of pooled statistically modeled MIC distributions were as follows: for amphotericin B, 4 μg/ml (F. verticillioides) and 8 μg/ml (F. oxysporumSC andF. solaniSC); for posaconazole, 2 μg/ml (F. verticillioides), 8 μg/ml (F. oxysporumSC), and 32 μg/ml (F. solaniSC); for voriconazole, 4 μg/ml (F. verticillioides), 16 μg/ml (F. oxysporumSC), and 32 μg/ml (F. solaniSC); and for itraconazole, 32 μg/ml (F. oxysporumSC andF. solaniSC). Insufficient data precluded ECV definition for the other species. Although these ECVs could aid in detecting non-wild-type isolates with reduced susceptibility to the agents evaluated, the relationship between molecular mechanisms of resistance (gene mutations) and MICs still needs to be investigated forFusariumspp.