The pulmonary response to a bacteremic challenge.

The pulmonary response to a bacteremic challenge was studied in a mouse model. The distribution of intravenously injected radiotracer-labeled Proteus mirabilis and Staphylococcus aureus in the lungs, liver, spleen, kidney, and blood was examined at 0, 5 30, 60, and 240 min. Pulmonary killing of these organisms was studied at 0, 30, and 240 min; 0.8 plus or minus 0.1 per cent of the P. mirabilis and 1.5 plus or minus 0.2 per cent of the S. aureus remained within the lungs after 4 hours. Although only 2.2 plus or minus 0.2 per cent of the P. mirabilis organisms were alive, 33.8 plus or minus 8.8 per cent of the staphylococci remained viable after this period. Light and electron micographs verified that polymorphonuclear leukocytes phagocytized these bacteria. The defense mechanisms of the lung against bloodborne and airborne bacterial infection are functionally, as well as morphologically, distinct.