Antifungal Pharmacodynamic Characteristics of Amphotericin B against Trichosporon asahii, Using Time‐Kill Methodology

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Abstract
We determined the MIC of amphotericin B against 45 Trichosporon asahii isolates from various clinical and environmental sources, and used in vitro time‐kill methods to characterize the relationship between amphotericin B concentrations and MIC for four representative T. asahii isolates. Amphotericin B had concentration‐dependent antifungal activity. MICs ranged from 0.5 to 16 μg/ml, and most T. asahii isolates (76%, 34/45) were inhibited at safely achievable amphotericin B serum concentrations (≤ 2 μg/ml). However, 40% (18/45) of isolates were not killed at these concentrations (MFCs from 1.0 to 32 μg/ml). At concentrations ≥ 2 × MIC, amphotericin B exhibited fungicidal activity (< 99.9% reduction in CFU) over a 12‐hr time‐period; the maximal effect was achieved at ≥ 4 × MIC. Susceptibility testing confirmed the resistance of T. asahii to amphotericin B, and in vitro pharmacodynamic results also suggest that amphotericin B is not suitable therapy for T. asahii infection.