The limited role of pneumolysin in the pathogenesis of pneumococcal meningitis

The aim of this study was to determine the role of pneumolysin, an intracellular toxin of Streptococcus pneumoniae, in the pathogenesis of pneumococcal meningitis. Recombinant pneumolysin (1 μg), when injected intracisternally into rabbits, resulted in a brisk inflammatory response. However, a pneumolysin-deficient strain of S. pneumoniae caused meningeal inflammation in rabbits indistinguishable from that induced by the parent pneumolysin-producing strain. Furthermore, similar enhancement of meningeal inflammation occurred after ampicillin therapy in animals infected with either the parent strain or the pneumolysin-deficient mutant. These results suggest that although pneumolysin can stimulate the inflammatory cascade in the central nervous system, it is not necessary for the pathogenesis of meningeal inflammation nor does it playa role in postantibiotic enhancement of meningeal inflammation.