抄録
Studies were perfomed on the unique E 46 and E 97 strains of staphylococci, which had been described in the preceding part of this series, to find any evidence for high virulence for mice by intraperitoneal inoculation. The results were compared with those obtained from the typical Staphylococcus aureus and S. epidermidis represented by the E 111 and B 217 strains, respectively.
When inoculated into mice by the intraperitoneal route, organisms of both unique strains were hardly ingested by the intrapeitoneal cells within about 2 hours. They began to multiply in abundance in the peritoneal cavity several hours later and invaded into the phagocytes almost simultaneously. Their multiplication finally led to destruction of the host cells. Then the organisms seemed to move into the blood stream and spread into almost all the tissues and organs to cause septicemia and death of the host, judging from the results of infection experiments mentioned in the preceding report. On the contrary, organisms of the B 217 strain were easily ingested and digested by the phagocytes. Those of the E 111 strain behaved in an intermediate manner between the above two.
The unique strains were able to grow well in human and rabbit sera like the E 111 strain. The B 217 strain, however, decreased in number in these sera. In mouse serum the growth of any tested strain was not affected at all.
The unique strains were proved to be negative for coagulase and α-hemolysin activities in routine quantitative assay. Every tested strain was positive for these activities, but very low in hemolysin titer for mouse erythrocytes.
Thus, it may be concluded that the high virulence of both unique staphylococcal strains for mice by intraperitoneal inoculation is derived mainly from their strong resistance against phagocytosis by the intraperitoneal cells at the early stage of infection and also from their vigorous ability to multiply inside and outside the phagocytes. The resistance may be attributed to the surface structure and function of those unique strains of whose cells were demonstrated to have a capsule-like structure and contain cell-wall ribitol, as described in the preceding paper.
