Minimum fungicidal concentrations of amphotericin B for bloodstream Candida species

Minimum fungicidal concentrations (MFCs) of amphotericin B were obtained for 165 bloodstream isolates (104 Candida parapsilosis, 14 C.glabrata, 13 C.tropicalis, 15 C.krusei, and 19 C.albicans) and 36 C.dubliniensis from oropharyngeal infections. Minimum inhibitory concentrations (MICs) were determined by the M27-A microdilution method. MFCs ( greater than or equal to99.9% killing) were obtained following MIC determination (inoculum size, 10(4) CFU/ml) by seeding the entire volume of all clear wells. The best fungicidal activity was for C. albicans, (MFC90 1 mug/ml) and the lowest for C.parapsilosis, C.tropicalis and C.glabrata (MFC90 16 mug/ml). Although MFCs were greater than or equal to16 x MIC for some isolates, including C. glabrata, the overall MFCs were greater than or equal to2 x MICs. However, major differences between MICs and MFCs were observed for C.parapsilosis and C.dubliniensis (3.8% and 8.9%, respectively, were tolerant: MFC greater than or equal to32MIC). MFCs for C.tropicalis and C. glabrata were greater than or equal to2 mug/ml. By this more stringent method we found substantial differences from those previously reported between amphotericin B MIC and MFCs for Candida spp. (C) 2003 Elsevier Science Inc. All rights reserved.