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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, METHODS, RESULTS. Meshes: Animals, Bacterial Proteins, Disease Models, Animal, Genes, Bacterial, Male, Meningitis, Pneumococcal, N-Acetylmuramoyl-L-alanine Amidase, Rats, Rats, Wistar, Streptococcus pneumoniae, Streptolysins, Virulence, Virulence Factors.
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Does streptococcus pneumoniae deficient in pneumolysin or autolysin have reduced virulence in meningitis? Context: The role played by pneumolysin and autolysin in pneumococcal meningitis is poorly understood. A rat model was used to investigate the disease, in which surgical implantation of a cisternal catheter allowed bacterial instillation and cerebrospinal fluid (CSF) sampling. CSF infection of rats with wild-type pneumococci caused meningitis within 26 h, whereas isogenic mutants that do not express pneumolysin (DeltaPly) or autolysin (LytA(-)) caused very mild or no disease. Wild-type infections resulted in pneumococci in the CSF and cortical homogenates, but a minority of the rats infected with DeltaPly or LytA(-) had bacteria in these locations at 26 h. Leukocyte numbers in the CSF were similar after infection with all pneumococci; however, neutrophils and monocytes predominated after wild-type infection, whereas lymphocytes and atypical lymphocytes predominated after infection with the mutants. Wild-type pneumococci caused disruption to the ependyma, but this was not observed in rats infected with DeltaPly or LytA(-). Cells surrounding the ventricles in wild type-infected animals expressed caspase 3, and astrocytes had hypertrophy; both findings were absent in rats infected with the mutants.
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This study provides strong in vivo evidence that pneumolysin and autolysin play crucial roles in the pathogenesis of pneumococcal meningitis. Final Decision: yes