Increased susceptibility of splenectomized mice to infection after exposure to an aerosolized suspension of type III Streptococcus pneumoniae.

Most reported experimental studies concerning the effect of splenectomy in animals have shown enhanced mortality from pneumococci injected either intravenously or intraperitoneally. We have developed a laboratory model in which mice are exposed to type III Streptococcus pneumoniae via an aerosolized atmosphere, thus closely approximating the route of human infection with this organism. Ninety-one male Swiss mice (mean weight 26 g) were divided into three approximately equal groups of control, sham-operated, and splenectomized animals. Two weeks later they were exposed for 30 min in individualized compartments within a confined chamber to an aerosolized atmosphere producing a uniform challenge of 5.9 X 10(9) colony-forming units per ml of pneumococci. A statistically significant increase (P less than 0.01) in mortality was demonstrated in the splenectomized group over the pooled sham-operated and control groups. The animal model used in these investigations can be applied to the study of infections acquired by the respiratory route in numerous experimental designs.