1990 Volume 43 Issue 6 Pages 616-622
A54145 complex is made up of eight factors; A, A1, B, B1, C, D, E, and F which were active in vitro (MIC 0.25- > 32μg/ml) against Gram-positive aerobic organisms. The complex, factors B and B1 were found to be active against two strains of Clostridiumperfringens. A calcium dependence study on some of the factors showed that their in vitro antibacterial activity was greatly enhanced by the presence of calcium (50 mg/liter) in the media. Resistance build-up was seen when Staphylococcus sp. and Streptococcus sp. were passed seven times in the presence of sublethal concentrations of A54145 antibiotics. This resistance disappeared immediately when the resistant organisms were passed in the absence of the antibiotics. Factor A was very effective against Staphylococcus aureus and Streptococcuspyogenes infections in mice (sc ED50s of 3.3-2.4 mg/kg × 2, respectively). Factor B was more active against S. pyogenes in vivo (sc ED50, 0.9 mg/kg × 2). Acute mouse toxicities were determined with these antibiotics. Semisynthetic derivatives were evaluated.
