Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 17 2 2025 04 05 220 228 Dhafer Rasheed Al-Fetly Department of Internal and Preventive Medicine, College of Veterinary Medicine, University of Al-Qadisiyah, Al-Diwaniyah, Iraq Atiaf Ghanim Rhyaf Department of Pathology, College of Veterinary Medicine, University of Al-Qadisiyah, Al-Diwaniyah, Iraq Hala Abbas Naji Department of Pathology, College of Veterinary Medicine, University of Al-Qadisiyah, Al-Diwaniyah, Iraq 2024 01 05 2025 02 23 Background and Objectives: Staphylococcal enterotoxin B (SEB), a potent superantigenic toxin produced by Staphylococcus aureus (S. aureus), plays a crucial role in S. aureus systemic infection. This investigation sought to determine whether immunising animals with SEB toxoid could protect against an experimental acute systemic infection caused by S. aureus. Materials and Methods: This study involved three groups of animals: one group was administered with SEB toxoid, and the second group was administered with intramuscular injections of normal saline, after which both were subjected to systemic S. aureus infection. The third group served as the negative control. After two weeks, the outcomes of the experimental systemic infection demonstrated that SEB immunisation significantly shielded organs (lung and liver) from damage in comparison to the control group. Results: Regarding the histopathological analysis of liver and lung tissues, the control group showed minimal alterations, indicating a normal tissue state. Infected individuals exhibited severe pathology, including inflammation, necrosis, and fibrosis. The immunised group displayed a mixed profile with elevated inflammation but lower necrosis and fibrosis. Immunisation mitigated pathological changes induced by infection, fostering a more controlled response. Conclusion: SEB plays an important role in S. aureus pathogenesis and immunisation, and this toxoid might protect against fatal infections of S. aureus. https://ijm.tums.ac.ir/index.php/ijm/article/view/4537 https://ijm.tums.ac.ir/index.php/ijm/article/download/4537/1760