Histopathological Assessment of Lung Tissue in Wistar Rats with Pneumonia Induced by Staphylococcus aureus

Background Staphylococcus aureus is a commensal bacterium capable of transitioning into a pathogenic form under favorable conditions, resulting in a wide spectrum of infections. It accounts for approximately 20–50% of hospital-acquired pneumonia (HAP) cases and 25.5% of community-acquired pneumonia (CAP), both of which are associated with substantial morbidity and mortality. The ability of S. aureus to cause severe respiratory illness is of increasing clinical concern, particularly in settings with limited diagnostic and therapeutic resources. Objective This study aimed to evaluate the histopathological alterations in lung tissues of Wistar rats experimentally infected with S. aureus strains isolated from pneumonia patients, and to assess the severity of infection associated with different strains. Methods A total of 1,500 sputum samples were collected from pneumonia patients in randomly selected hospitals across Nigeria. Standard microbiological techniques were employed for the isolation and identification of S. aureus , yielding 79 positive isolates. These isolates were subcultured and used to inoculate healthy Wistar rats intranasally. After a 14-day incubation period, the rats were euthanized, and lung tissues were excised and processed for histological examination using hematoxylin and eosin (H&E) staining. Results Histopathological analysis revealed pronounced pulmonary lesions, including alveolar congestion, infiltration of inflammatory cells, thickening of alveolar septa, and accumulation of exudates and purulent material. Some strains—CU82, CA26, CSA24, CU14, CA43, and CA58—exhibited enhanced virulence, causing more severe tissue destruction. Conclusion This study demonstrates the substantial histopathological damage caused by S. aureus -induced pneumonia and underscores the importance of strain-specific virulence in disease severity. The findings may inform clinical approaches to the diagnosis and management of S. aureus -related pneumonia.