ANTIBACTERIAL SUBSTANCES FROM STAPHYLOCOCCI

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Abstract
It was found that 4.9% of 1065 coagulase-positive and 8.5% of 387 coagulase-negative strains of Staphylococcus produced antibiotics inhibiting growth of the indicator strain, Staphylococcus aureus Oxford 209P.Zones of inhibition on solid media ranged from slight to 6 mm. Antibiotics produced by several of the most active strains were investigated in detail. With one or two exceptions, these substances inhibited the growth of Gram-positive rather than Gram-negative bacteria. Most staphylococcal strains were found to be more sensitive to antibiotics produced by coagulase-negative than positive strains selected. At the concentration used, these antibiotics did not kill all cells of the indicator strain, S. aureus 209P.The activity of the antibiotics was not totally destroyed by autoclaving or proteolytic enzymes, and was unaffected over the pH range 2.0–11.0. The antibiotics were dialyzable and their activity was inhibited by 10−3 M concentrations of EDTA but not by citrate.