Repression of Staphylococcus aureus in associative culture.

The growth of Staphylococcus aureus MF 31 was suppressed when grown in association with Streptococcus diacetilactis and other lactic streptococci. The data indicated that the initial proportion of staphylococci present in the medium was of less importance than the depletion of vital nutrients. Investigation revealed that factors present in Yeast Nitrogen Base medium could reverse the inhibition which was due to antagonism. The major factor found was nicotinamide, and further study revealed that the biological availability of this compound was influenced by the pH of the medium. The addition of nicotinamide to depleted media with careful control of the pH resulted in increased growth of S. aureus in the test system. Further data indicated that additional factors may affect the degree of growth by S. aureus in depleted media.