We have been working on the interaction between Staphylococcus aureus cells and L929 fibroblasts in connection with the infectious foci formed in mouse kidney. We reported that fibroblasts ingested many bacteria in spite of a non-phagocytic cell, and turned to necrotic or apoptotic. In our previous experiment, staphylococcal cells in early exponential phase appeared to be more virulent to cultured fibroblasts than those in stationary phase. The aim of this study was to examine the capability of S. aureus cells in the two growth phases for forming infectious foci, and to discuss the association of the renal disability with the cultured fibroblasts in necrosis or apoptosis.
S. aureus OK11 cells grown in brain heart infusion for 2 hr (exponential phase) and 20 hr (stationary phase) were used. Thirty minutes and 1 day after the intravenous inoculation of S. aureus cells, mouse kidneys were removed, and the number of bacteria in kidney homogenate was measured. Morphological study about the infected kidney was also performed.
More staphylococcal cells in exponential phase could adhere to and vigorously multiply in kidney than those in stationary phase. One day after the injection of bacteria in exponential phase, extremely large amount of bacteria were observed on renal corpuscle which might be the first infectious part, and bacterial masses were also seen around the proximal convoluted tubules. Some abscesses were both near the surface and in the cortex of kidney.