Comparison of posaconazole and voriconazole in vitro killing against Candida krusei

The in vitro activity of posaconazole and voriconazole was evaluated by MIC, minimum fungicidal concentration (MFC), and time-kill methods. MFCs were determined for 15 Candida krusei and time-killing curves for 5 of these isolates. MFCs were obtained transferring 100 mu L from clear MIC wells onto Sabouraud dextrose agar. Time-kill studies were performed in RPMI 1640 medium (5 mL, inoculum approximate to 10(5) colonyforming unit [CFU]/mL). Geometric mean (GM) MIC and GM-MFC were 0.2 and 0.72 mg/L for posaconazole and 0.4 and 2.64 mg/L for voriconazole. The killing, rate was isolate and concentration dependent; reductions in CFUs start at >= 0.12 mg/L (posaconazole) and >= 0.5 mg/L (voriconazole). The mean time to reach a 90% growth reduction was 41.5 +/- 14.2 h (8 mg/L posaconazole) and 48.7 61.3 h (32 mg/L voriconazole). By time kill, a 99% killing rate was not reached by either agent. Both methods demonstrated that posaconazole (more active and greater killing rate) and voriconazole have fungicidal activity against C. krusei. (C) 2008 Elsevier Inc. All rights reserved.