Comparative in vitro antifungal susceptibility activity of amphotericin B versus amphotericin B methyl ester against Candida albicans ocular isolates

Purpose: To compare in vitro susceptibility of amphotericin B (AMB) and amphotericin B methyl ester (AME) (a more soluble and less toxic formulation of AMB) against Candida albicans isolates recovered from human cases of endophthalmitis. Methods: The in vitro susceptibility of AMB and AME was determined for C. albicans isolates recovered from endophthalmitis (N=10) and for C. albicans ATCC reference strain 90028 using the Clinical and Laboratory Standards Institute M27-A2 (NCCLS/CLSI) broth dilution method. All isolates were obtained from samples of vitreous humor of patients with suspected endophthalmitis within the last 5 years at the Bascom Palmer Eye Institute, University of Miami Miller School of Medicine (Miami, FL). Results: The minimal inhibitory concentrations (MICs) of AME were equal to or lower than values for AMB in 7 of the 10 isolates; range: AME (0.125-1μg/mL) versus (0.5-1μg/mL) for AMB. The MIC₉₀ value of both drugs was equal (1μg/mL). Compared with AMB, the minimal fungicidal concentrations (MFCs) of AME were equal to or lower in 8 of 10 isolates; range: AME (0.125-2μg/mL) versus AMB (0.25-4μg/mL). MFC₉₀ values of AME (1μg/mL) was slightly superior to AMB (2μg/mL). The MIC of the quality control strain (ATCC ^® 90028) was within an acceptable range. Conclusions: AME was equivalent to AMB in vitro against C. albicans. This formula may offer a slightly more efficient and less toxic formulation for the treatment of Candida endophthalmitis.