Preparation of a Modified Subtilin Suitable for the Treatment of Tuberculosis and Other Infections in Animals.

Subtilin is an antibiotic extracted from the cells of a particular strain of Bacillus subtiliws.3" It is a low molecular weight substance that dialyzes through collodion membranes, is sensitive to light and alkali, and has the structure of a peptide. Subtilin is soluble to at least 30 per cent in saltfree acidified solution. The solubility in acid solution is markedly decreased by the presence of salt. In the presence of 0.5 to 1 per cent of sodium chloride the solubility is reduced to approximately 0.5 to 0.2 per cent. The addition of serum to an aqueous solution of subtilin produces a marked precipitation. The antibiotic is probably a basic substance giving water-soluble salts (1). The antibacterial spectrum of subtilin (2) is similar to that of penicillin. It seems reasonable to postulate that the antibiotic might prove useful in infections caused by penicillin-fast or penicillinresistant organisms. In addition, subtilin is effective against Mycobacterium tuberculosis which is not antagonized by penicillin. The low solubility of subtilin in salt solutions and in serum is probably a desirable property in the treatment of infections caused by such organisms as the pneumococcus (3), streptococci (4), micrococci (5), the anthrax bacillus (6), etc., in which relatively small doses are required. Precipitation of the antibiotic in the presence of body fluids should slow down its elimination, thus giv-