Protection from postsplenectomy sepsis: Effect of prophylactic penicillin and pneumococcal vaccine on clearance of type 3 Pneumococcus.

The intravascular clearance of type 3 Streptococcus pneumoniae was studied in Sprague-Dawley rats. One hundred animals were divided into the following five equal groups: I--splenic mobilization, II--splenectomy, III--splenectomy plus pneumococcal vaccine, IV--splenectomy plus 50,000 U of penicillin prophylaxis, V--splenectomy plus 300,000 U of penicillin prophylaxis. Bacteremia was induced by intraperitoneal injection of 10(6) type 3 S. pneumoniae. Serial cultures of peripheral blood were obtained. Splenectomy produced significant impairment of intravascular clearance of Pneumonococcus compared to clearance in control animals (P less than 0.01). Neither dose of penicillin, administered prophylactically prior to induction of bacteremia, significantly altered pneumococcal clearance of asplenic animals. Administration of polyvalent pneumococcal vaccine to splenectomized rats resulted in measurable antibody titers. More importantly, such immunization of asplenic animals significantly improved pneumococcal clearance compared to clearance in asplenic, nonimmunized rats (P less than 0.03). Although in both groups I and III animals S. pneumoniae organisms were effectively removed from the peripheral blood, the clearance curves are significantly different (P less than 0.01). This represents the difference between phagocytosis by the reticuloendothelial cells of the liver and those of the spleen.