Effects of intrarenal inoculation of Staphylococcus aureus on mice.

The extreme susceptibility of the mouse kidney to infection with Staphylococcus aureus was confirmed by direct intrarenal (i.r.) inoculation with this organism. By applying Poisson's distribution formula to the results from infection of mice with small inocula (as few as one coccus or less per kidney), it was estimated that even three organisms could multiply in situ to produce abscess lesions, if the organisms were inoculated directly into the kidneys. This susceptibility of the mouse kidney for staphylococcal infection was not uniformly manifested with every strain, but correlated well with the virulence found through intravenous infection of the strains tested. The i.r. inoculation method by which infection of mice was easily established, using a small inoculum of S. aureus, similar to the amount suspected to occur in natural infections of man, is applicable for the analysis of the mechanisms of staphylococcal infections and any resulting immunity in man. The present paper describes the details and some experimental results obtained by our method.