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| Author(s): |
Camila Freitas Batista
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2015-09-11 |
| Examining board members: |
Alice Maria Melville Paiva Della Libera;
Fernando José Benesi;
Roberto Calderon Gonçalves;
Marcos Bryan Heinemann;
Rinaldo Batista Viana
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| Advisor: | Alice Maria Melville Paiva Della Libera |
| Abstract | |
Mannheimia haemolytica is an important bacterial pathogen associated with Bovine Respiratory Disease Complex (BRDC) and it is believed to be the predominant cause of the disease’s evolution into a fibrinonecrotic pneumonia. A commensal inhabitant of the nasopharynx, M. haemolytica acts as an opportunist when host defenses are compromised. This study used an experimental infection model to investigate the possible local and systemic changes caused by M. haemolytica in inoculated calves. It sought to linearly follow the dynamics of the lower respiratory tract defense mechanisms, during the course of infection and after treatment with the antibacterial norfloxacin, which was administrated both with and without the anti-inflammatory flunixin meglumine. With clinical examination followed by bronchoscopy, this study evaluated the physiological modifications in defense cells and mediators of inflammation, and the in vitro influence of norfloxacin on phagocytes from the peripheral blood and Bronchoalveolar Lavage Fluid (BLF). Twelve (12) healthy calves were infected with M. haemolytica and posteriorly physically examined, and had samples of white cells from the peripheral blood and BLF analyzed for changes in count and physiology, further, the norfloxacin effect on phagocytes from the peripheral blood and BLF was also studied. The experimental infection proved itself to be successful based on clinical, bronchoscopic and cytological findings. Furthermore, the M. haemolytica experimental infection was associated with modifications in the subpopulations of lymphocytes CD8+ and уδ T cells, in intracellular production of Reactive Oxygen Species (ROS), viability and phagocytosis activity of CD14+ cells from the peripheral blood and BLF and granulocytes from the peripheral blood. No obvious change was observed in the expression of cytokines IL-1β, IL-8 e TNF-α by cells from the peripheral blood or BLF. The treatment with the antibacterial agent, with or without the anti-inflammatory, was proved to be successful in curing the disease, thus, the addition of an anti-inflammatory was considered unnecessary to revert the clinical infection and in the immune response. Although there was a systemic response during the course of infection, the local response was more noticeable. Another key finding of the present study was the in vitro effect of norfloxacin on the intracellular production of ROS and on phagocytosis activity of CD14+ cells from the peripheral blood and BLF and granulocytes from the peripheral blood. In conclusion, the functional changes in phagocytes play an important role in the pathogenesis of pulmonary infection caused by M. haemolytica, as they were consistent with the clinical findings of mannheimiosis and with the treatment when it was administrated in the beginning of the infection. (AU) | |
| FAPESP's process: | 11/23936-6 - Dynamics of blood and alveolar phagocytes in calves with mannheimiosis |
| Grantee: | Camila Freitas Batista |
| Support Opportunities: | Scholarships in Brazil - Doctorate |