Antibacterial Substance in Human Serum Against Nonpathogenic Staphylococcus

Abstract

Normal human serum contains an inhibitor which prevents the growth of non-pathogenic staphylococci. The inhibitor was named delta-factor. Properties of the factor were examined and the following results were obtained.
Nutritional requirement of the bacteria was independent of the factor.
The activity of the factor was not interfered with coagulase.
The abilities of bacteria to produce coagulase and DNase were not related to the action of the inhibition phenomenon.
The activity of the factor was stable and most active at pH 7.5-8.5 in ionic strength 0.05-0.25.