Inhibition of Pseudomonas aeruginosa slime production by staphylococcal extracellular product.

Staphylococcus aureus produced an inhibitory factor that suppressed slime formation by Psuudomonas aeruginosa but had little effect on the growth of the organism. The inhibitory factor was not found in broth cultures but could be extracted from cultures grown on solid agar. The inhibitory factor moderately inhibited gram-negative bacteria in addition to inhibiting a variety of gram-positive bacteria. The inhibitory factor was found to have a low molecular weight, as judged by its diffusibility, and it could be partially purified by gel filtration on Sephadex G-50. It was observed to be heat labile; however, its activity was stable within a wide pH range. The factor was resistant to deoxyribonuclease, ribonuclease, and lipase, but sensitive to trypsin. The role of the inhibition of slime production in pathogenicity is discussed.