Behaviors of a Vigorous Protease-Producing Strain of Staphylococcus aureus in the Skin Tissue of Mice

The behaviors of a protease-producing strain of Staphylococcus aureus, including the production of α- and β-hemolysin, protease, and nuclease in the skin tissue of mice, were examined by the fluorescent antibody technique and hematoxylin and eosin staining. When about 106 viable cells were subcutaneously inoculated into a mouse, they were phagocytized by leukocytes and a suppurative focus developed in situ. No active extracellular substances other than α-hemolysin were demonstrated in this mouse. When 107 viable cells were inoculated, most of them were also phagocytized by leukocytes, and a rather large suppurative focus was formed. In this focus a low degree of multiplication of the organisms was observed. Protease and α-hemolysin could be detected in the neighborhood of the leukocytes. When 108 to 109 cells were inoculated, they multiplied transitorily in the subcutaneous tissue and produced the four substances mentioned above. The multiplication of bacterial cells as well as the production of extracellular substances ceased within a comparatively short period and the transitory state was similar to that in a batch fermenter. Necrotic and histolytic lesions were observed only in the mice inoculated with 108 to 109 viable cells. Similar dermatolytic lesions were also found in mice injected with 0.5 to 1.0 mg of pure protease.