AMINO-ACID CHANGES AFFECTING THE ACTIVITY OF PNEUMOLYSIN ALTER THE BEHAVIOR OF PNEUMOCOCCI IN PNEUMONIA

Pneumolysin is a multi-functional toxin produced by Streptococcus pneu moniae. The toxin has distinct cytotoxic activity and complement-activ ating activity mediated by different parts of the toxin molecule. Mice challenged intranasally with a type 2 pneumococcal strain contract br onchopneumonia and bacteremia [1]. Mice were infected intranasally wit h isogenic mutants of this strain in which the chromosomal pneumolysin gene carried point mutations affecting either or both properties of p neumolysin. Reduction in either cytotoxic activity or complement activ ation by pneumolysin decreased the virulence of the mutant pneumococci . However, it was the ability to activate complement that most affecte d the behaviour of pneumococci in the lungs and associated bacteremia in the first 24 h following infection. (C) 1998 Academic Press Limited .