Pneumolysin-mediated organ damage: Histopathological assessment of Streptococcus pneumoniae virulence in laboratory mice

Background: Streptococcus pneumoniae is still among the principal causes of respiratory infections across the world. Pneumolysin is the virulence factor most important for pathogenesis and tissue injury. This research has been designed to study the histopathological impacts of pneumolysin of clinically isolated S. pneumoniae on the vital organs of laboratory mice. Methods: Fiftу blood samples were drawn from patients exhibiting symptoms of pneumonia. S. pneumoniae isolates were identified through biochemical tests and the VITEK 2 Compact system and confirmed by PCR amplifying the pneumolysin genes. Laboratory mice were divided into four groups and injected with bacterial suspensions of 10⁵-10⁷ CFU/mL. A histopathological study was performed on the kidney, liver, spleen, and lung tissues. Results: S. pneumoniae was successfully isolated from 32 out of 50 blood samples. Histopathological examinations showed degeneration in all tissues in every organ. The kidney showed glomerular cellular infiltrates, nephron atrophy, and Bowman's capsule expansion. The liver with hepatocyte necrosis, dilation of hepatic sinusoids, and granuloma formation adjacent to hepatic veins. Lung tissues with congested blood vessels, infiltrates of inflammatory cells, and thickened interalveolar walls. The spleen with fibrous connective tissue between the follicles of the lymphatic glands. The level of destruction increased with the bacterial concentration. Conclusion: The multifunctional organ damage from pneumolysin in the kidneys, spleens, lungs, and livers of laboratory-based mice indicates the importance of virulence factors in the pneumococcal infection-host relations and highlights the need and importance of prompt treatments to limit the histopathological damage of pneumococcal infections.