Study on a mutant strain of staphylococcus aureus No.248 which changes simultaneously in its β hemolysin producing ability, growth rate and virulence for mice

Abstract

Perhaps it will give a powerful key for analysis of mechanism of “Infection and Immunity” in staphylococcal disease to isolate and use several mutants which originate from the same one strain but are clearly different qualitatively of quantitatively-each other in their pathogenicity for a certain sensitive animal.
We could recently isolate a β hemolysin producing mutant from the culture of staphylococcus aureus No.248 strain which had been stocked in our department.
This mutant 248 βH has at the same time proven to be different from the original strain in showing a rather favourable growth in ordinary culture media and a higher pathogenicity for mice. And there has not yet found any difference between these two strains besids these three characters above mentioned.
On the point of view, we have at first compared these two strains especially in their pathogenicity for mice. The results of experiment are as follows.
The LD₅₀ of 248 βH is about 0.1mg (in wet cell weight) in intravenous challenge while the i. v. injection of even 2.5mg of 248 orig strain could only kill one of five mice.
It is rather interesting that AD₅₀, dosis enough to produce kidney abscess in 50% of infected mice, of 248βH is 0.008mg, about one tenth of its LD₅₀.
It indicates that the more production of kidney abscess does not induce the dead of the infeced mice, and in other words the mice having abscess in their kidneys does not almays all die.
Our central thema in future will be to analyse what essentially determines the lethality of mice infected with staphylococcus plassing α to kidney abscess and on the other hand what does rescue the mice with kidney abscess from dead plassing α to the host side.