In vitro anti-mycoplasmal activity of amphotericin B methyl ester.

The polyene macrolide antibiotic amphotericin B (AB) and its chemically modified derivative amphotericin B methyl ester (AME) were tested for in vitro activity against Acholeplasma laidlawii, Spiroplasma citri and Mycoplasma gallisepticum. Both polyene macrolide preparations demonstrated anti-mycoplasmal activity. However, AME was mycoplasmacidal toward all three strains of mycoplasma at levels which previous studies have indicated would be permissible for most cell culture systems, whereas the levels of AB required for similar activity would be physiologically intolerable for tissue culture cells. In addition, AME was 100 fold more active than AB toward A. laidlawii, 10 fold more active than AB toward S. citri and demonstrated equivalent activity as AB toward M gallisepticum. The in vitro anti-mycoplasmal activity of AME and AB was directly correlated with polyene macrolide antibiotic levels and the number of treated mycoplasma.