In vitro combined activity of amphotericin B, caspofungin and voriconazole against clinical isolates of Trichosporon asahii

Disseminated infections caused by Trichosporon asahii are difficult to resolve. Combination regimens with synergistic drugs could provide additional options for treating trichosporonosis. The aim of this study was to evaluate the antifungal activities of voriconazole (VCZ), caspofungin (CAS) and amphotericin B (AMB) alone or in combination in vitro against clinical isolates of T. asahii. The combined antifungal activities of VCZ, CAS and AMB against 18 clinical isolates were assessed by a chequerboard microdilution method. CAS combined with AMB showed the highest percentage of synergistic effects (89%), much higher than those of the other two combinations (AMB/VCZ and CAS/VCZ both 17%). No antagonistic effect was observed in any case. This study demonstrates that the activity of two combined antifungals, especially the combination of CAS and AMB, against T. asahii is more effective than that of a drug alone against this fungus, suggesting that combined antifungal therapy may be a potential strategy for treating disseminated trichosporonosis.