Protective Effect of Prophylactic Penicillin on Splenectomized Mice Exposed to an Aerosolized Suspension of Type III

Prophylactic penicillin has been recommended for use in asplenic patients and postsplenectomy patients. A laboratory model using aerosolized pneumococci has been devised to test the effectiveness of prophylactic penicillin in a manner analogous to human experience. There is increased mortality. over time, in asplenic mice exposed to aerosolized type Ill Streptococcus pneumoniae. One hundred twenty-one male Swiss mice (mean weight 26 g) were divided into four groups: splenectomized. sham-operated. splenectomized + penicillin. and sham-operated + penicillin. After 2 wk the four groups were exposed for 30 mm to an aerosolized atmosphere of 2.4 X 1 O colony-forming units of type III S. pneumoniae using a Tri-R model A-42 airborne infection apparatus. Penicillin was given at a daily intramuscular dosage of 40.000 units procaine penicillin G beginning 2 days prior to exposure and continuing through the third day after exposure. The splenectomized and shamoperated mice given penicillin showed significantly lower mortality (p < 0.001) than mice not given penicillin.