The Nature of Inhibitory Activity by Staphylococcus aureus Type 71

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Abstract
Antibiotic production in liquid media by Staphylococcus aureus strains of bacteriophage "type 71" was poor as measured by cup assays against susceptible corynebacteria. Aerobic incubation in freshly prepared tryptic-digest broth containing a fermentable carbohydrate and adjusted to pH 7.8 gave the greatest yields. The antibiotic material was not obtained in a pure state but was concentrated by evaporation of crude solutions. These were prepared by adding trichloroacetic-acid to broth cultures and centrifuging to remove the organisms. The antibiotic was stable and relatively heat-resistant under acid conditions but was rapidly destroyed when alkaline; it diffused slowly through cellophane, was adsorbed by charcoal and was inactivated by trypsin but not by pepsin. These properties suggest that it maybe protein or polypeptide in nature. Inhibitory activity by type 71 cocci was shown in mixed broth cultures against other noninhibitory strains of Staphylococcus aureus and was similar to that previously observed on solid media.