Establishment of a pneumococcal septicemia model in the miniature swine

Human pneumococcal septicemia, the prominent postsplenectomy complication, was as yet difficult to study in the porcine model, since this species appeared to be fairly resistant against pneumococcal infections. We have used two strains of pneumococci (serotype 1 and 6B) both of which had been isolated from patients with systemic infection and both of which were maintained in a virulent state by regular mouse passage. After challenge with 10(9) type 1 pneumococci, however, only one of the 5 pigs developed fever, none showed profound hematological alterations and each animal exhibited a rapid clearance of bacteria from peripheral blood. By contrast, challenge of 7 animals with type 6B pneumococci resulted in a slower and incomplete bacterial clearance with persistent bacteremia for up to 24 hours. All animals developed fever and a profound leukopenia with less than 5,000 leukocytes/ml and 3 of the 7 animals died after injection of type 6B pneumococci. The results show that potentially the type 6B pneumococci can be successfully employed for studies of gram positive septicemia in the miniature swine.