Effects of voriconazole combined with micafungin against 101 isolates of Candida spp. and 100 isolates of filamentous fungi have been evaluated by in vitro checkerboard analysis. The combination was indifferent for 97% of the Candida isolates and synergistic for 64% of the filamentous fungi (79% for Aspergillus fumigatus).The combination of two antifungal agents, voriconazole (VRC) and micafungin (MFG), was assessed for synergism against clinically relevant yeasts and molds. So far, only one little in vitro study including 10 isolates of Aspergillus fumigatus has been performed on the specific combination of VRC and MFG (6,9). In the present study, we have investigated the in vitro interaction between VRC and MFG by checkerboard assays against 196 clinical isolates from patients, including fluconazole-resistant strains from human immunodeficiency virus-infected patients (15) The assay preparation for Candida was performed in accordance to NCCLS document M27-A2 (17). Since the NCCLS M38-A (16) reference method for testing filamentous fungi does not give recommendations for in vitro testing of echinocandins, minor modifications were necessary. Several preliminary tests demonstrated an incubation temperature of 37°C and an incubation time of 24 h (11, 12) as optimal conditions. Conidia were counted on a hemocytometer. Measuring the metabolic activity by the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazoliumhydroxide (XTT) colorimetric method was used to determine the MIC endpoints (10). Standard antifungal powder of VRC was provided by Pfizer (New York, N.Y.), while MFG was provided by Fujisawa (now Astellas Pharma Inc., Tokyo, Japan). The final concentration of the antifungal agents ranged from 0.0156 to 4 g/ml for VRC and from 0.002 to 128 g/ml for MFG. The interactions were investigated by a checkerboard titration broth microdilution-based method. 96-well round-bottom plates (Corning BV, SchipholRijk, The Netherlands) were prepared with twofold concentrated RPMI 1640 medium (with L-glutamine, without bicarbonate)

The in vivo effect of posaconazole in zygomycosis needs further evaluation.