In Vitro Activity of Isavuconazole against Trichosporon species

George R. Thompson III, Nathan P. Wiederhold, Deanna A. Sutton, Annette Fothergill, Thomas F. Patterson

Abstract: 

Background: The emergence of less common, but clinically important, fungal pathogens including Trichosporon has contributed to the substantial morbidity and mortality observed in immunocompromised patients. This genus, which has recently undergone extensive taxonomic revisions, can be resistant or refractory to existing antifungal agents, particularly the echinocandins. We sought to evaluate the activity of the new triazole Isavuconazole against different Trichosporon species.
Methods: Trichosporon species were identified using the API 20CAUX yeast ID system, microscopic morphology, temperature studies, and cycloheximide susceptibility. Minimum inhibitory concentrations (MICs) were measured for Isavuconazole, voriconazole, posaconazole, fluconazole, amphotericin B, and flucytosine against 54 Trichosporon species (40 T. asahii, 10 T. mucoides,, and 4 T. inkin) in accordance with the M27-A2 reference method. Minimum fungicidal concentrations were also measured for each agent.
Results: Isavuconazole demonstrated excellent in vitro activity against all tested isolates. MIC50 values ranged from 0.06 to 0.125 mg/L, and MIC90 values ranged between and 0.125 to 0.25 mg/L. No MICs greater than 0.25 mg/L were observed. The geometric mean MICs of Isavuconazole were similar to that of voriconazole and similar or less than those of posaconazole, fluconazole, amphotericin B, and flucytosine for all species tested. The MFC50 and MFC90 values for the extended spectrum triazoles including Isavuconazole were lower than those of fluconazole, amphotericin B, and flucytosine. However MFC90 values often exceeded the highest concentration tested and exhibited wide variability.
Conclusions: Isavuconazole is a welcome addition to the growing antifungal armamentarium with potent in vitro activity against Trichosporon spp. Although this agent may be useful in the treatment of trichosporonosis clinical data are needed to verify these results.

abstract No: 

PP-03-11
    • ISHAM 17th (2009)