Amphotericin B is a heptaene isolated from a Streptomyces. It has a marked inhibitory activity on Blastomyces dermatitidis in vitro and a curative activity on experimental blastomycosis in mice and hamsters. In vitro, the growth of the mycelium phase experiment on four strains of B. dermatitidis is inhibited during 10 days by 0.1 microgramscc Sabouraud liquid medium. The growth of the yeast phase is inhibited, by 0.7 microgramscc blood-cysteinbrin- heart medium. In vivo, 100 of the mice and hamsters inoculated intraperitoneally with 1,000,000 B. dermatitidis yeasts survive when they receive amphotericin B, orally in dosages from 2 to 8 micrograms per animal. The death-rate of the controls is 100 within 4 weeks. But for a few exceptions, the treated animals do not present any anatomo-pathological lesions and the cultures of spleens, livers and lungs are negative. Amphotericin A and nystatin both tetraenes, administered orally, are inactive on experimental blastomycosis in mice and hamsters. The effect of subcutaneous injection of amphotericin B is similar to that of ingestion, but provokes a local reaction at the site of injection. Amphotericin B is not toxic at the dosages used in the experiments.
Trans. of Institut Pasteur, Paris. Annales (France) v93 p631-646, 1957.