Inter and Intraserotype Variations of Streptococcus Pneumoniae Pathogenicity in Mice and Rabbits

Abstract

The small mammalian labratory animals, the mice and the rabbits were tempted to be pathogenicity models for S. pneumoniae serotypes 1 and 6, the infecting doses were 0.3ml for mice and 0.5 ml for rabbits. These infectious doses were rated to a count of 1X 10 to 7 CFU/ml. The infection routes were intrapreritoneal for mice and intranasal for rabbits. The gold standard criteria for pathogenicity were the death end point DEP.DEP was up to 24hr for mice and ranged from four to 14 days in rabbits. Mice was more susciptable than rabbits for S. pneumoniae serotypes infections. Autopsy cultures of blood, lungs, liver and kideys were producing same infecting serotype both from mice and rabbits. This isolation profile was indicating bacterimic state induced by infection. Different serotypes have shown different death end points duration time. There were inter and intraserotype variations in DEP. Moderate to severe respiratory disease conditions RDC was noted in mice while mild RDC in rabbits. Both of the tested models were similar lung histology to man. The histological features of this experimental infections have shown that the infected mice and rabbits were of bronchopneumonia type. It appears that both mice and rabbits were standing as valid laboratory animal models for these local clinical isolates of S. pneumoniae serotypes.