Effect of the Live and Heat-Killed Cells of Staphylococcus aureus on the Resistance of Mice to the Infection with Nocardia asteroides

Abstract

When living cells of Staphylococcus aureus were introduced into mice by various routes within a few hours before or after infection with Nocardia asteroides, a marked increase in mortality and enhanced severity of lesions were observed. This effect was presumably caused by a heat-labile substance (s) liberated from the cells of S. aureus. No increase in resistance occurred when S. aureus was given 2 to 7 days before the nocardial infection, contrary to the effect of E. coli as reported previously. An increased resistance was noted when heat-killed cells of E. coli were administered two to four days before concurrent infection with N. asteroides and S. aureus.