Optimization of bioassay method for the quantitative microbiological determination of amphotericin B

The aim of this study was to find the optimal bioassay parameters for the quantitative analysis of an amphotericin B nasal spray solution as the bioassay conditions recommended by the Ph. Eur. 6. were less sensitive and were only applicable for the measurement of a narrow concentration range, which makes the method unsuitable in case of a stability test. We evaluated five commonly used assay media with Candida albicans and Saccharomyces cerevisiae as test organisms. Our results showed that Mueller Hinton Agar supplemented with 2% glucose and 0.5 μg ml⁻¹ methylene blue inoculated with C. albicans gave the best bioassay circumstance as a wide concentration range (1.54–60.0 μg ml⁻¹ amphotericin B) could be measured and the inhibition zone borders were distinct and easy to read.