Bacteriostatic and Bactericidal Substances Produced by a Soil Actinomyces.

SummaryThe bacteriostatic and bactericidal substance produced by a soil Actinomyces was shown to consist of 2 compounds, designated as "actinomycin A" and "actinomycin B". The first is highly pigmented (red) and is soluble in ether, ethyl alcohol and water, but not in petrol ether; it gives a clear solution in water. The second is soluble in ether and in petrol ether, soluble with difficulty in alcohol, but not in water. The first (A) is highly bacteriostatic, many Gram-positive bacteria being inhibited by dilutions of 1:100,000,000; the Gram-negative bacteria are inhibited only by higher concentrations, namely, 1:5,000 to 1:100,000; this substance is only weakly bactericidal. The second substance (B) is weakly bacteriostatic, but more actively bactericidal. Although Gram-negative bacteria are as a rule more resistant against the actinomycin than the Gram-positive forms, there is no sharp line of demarcation between the two groups. Marked differences in sensitivity exist between the bacteria within each group.