Contribution of capsular and lipopolysaccharide antigens to the pathogenesis of Klebsiella pneumoniae respiratory tract infection.

The role of Klebsiella pneumoniae K- and O-polysaccharide antigens was determined in a rat model of lobar pneumonia. The induction of experimental infection in rats by wild-type strain, and its lipopolysaccharide- and capsular polysaccharide-deficient mutants was compared. Though the mutant lacking both antigens (K- O-) induced infection it could not successfully establish itself in the rat lung. It caused only mild infection, as compared to the wild type strain (K+ O+) and the strain lacking CPS alone (K- O+). Besides capsular polysaccharide, the lipopolysaccharide antigen was shown to be an important factor in pathogenesis of K. pneumoniae acute respiratory tract infection.