1) Staphylococcus aureus 248 βH strain is one of the mutants producing β-hemolysine isolated from 248 orig. As was reported in the previous paper this mutant strain shows at the same time much higher virulenc for mice and rather better growth in ordinary nutrient media than those shown by the original strain.
The previous paper reported that 248 βH could occur by one step mutation from 248 orig. However, the subsequent studies revealed that sigregation could be seen at least between the ability of producing β-hemolysine and the virulence for mice.
2) The virulence of 248 βH for mice shown upon the intravenous infection primarily depends on its ability of growing in the mice kidney.
3) It would be likely considered that the following two phases could be separated in the course from the intravenous infection with 248 βH to the death of the infected mice: primarily the successful growth of 248 βH in the kiney of the infected mice and secondarily the attack of some unkown lethal agent produced chiefly in the kidney during the proliferation of the cocci against its target organ. However, neither the nature of that lethal agent nor its target organ have yet investigated in the present step of our studies.
4) The mice infected with sublethal dose of 248 βH retain for a long time, the survivals of cocci in their kidney and show a stable and strong resistance against the superinfection of the same or the homologous virulent strain of staphylococci.
5) The resistance of such high level as those observed in the mice being infected with 248 βH could not be aquired by the pretreatment of mice with the large dose of living organisms of 248 orig or killing vaccine of 248 βH although the latter two treatments could make the mice to survive a little longer than untreated control mice.
6) Some advantages of the characters provided by this experimental system for the analysis of the staphylococcal infection and its immunity were disscussed.
