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 microg ml(-1) methylene blue inoculated with C. albicans gave the best bioassay circumstance as a wide concentration range (1.54-60.0 microg ml(-1) amphotericin B) could be measured and the inhibition zone borders were distinct and easy to read.