| Summary: | 碩士 === 國立中興大學 === 獸醫病理學研究所 === 90 === Salmonellosis is among the most important bacterial diseases in swine worldwide, and the causative agents S. choleraesuis and S. typhimurium can induce systemic septicemia and gastroenteritis. The purpose of this study is to evaluate the phagocytic activity and respiratory burst in peripheral blood phagocytes (PBP) against S. choleraesuis and S. typhimurium via a whole blood model using flow cytometric analysis. The results demonstrated that S. choleraesuis possessed a higher invasive activity and induced less respiratory burst reaction than S. typhimurium in neutrophils and monocytes. Moreover, the age variation were also analyzed and the invasive activity of S. choleraesuis showed 2 fold higher than S. thyphimurim in 5-week and 8-week old pigs, but there were no differences in 3-week and 12-week old pigs. The respiratory burst reaction induced by S. choleraesuis in neutrophils was 1.75-2.17 fold less than S. typhimurium, but no significant variation was noticed in monocyte. That results revealed thst S. choleraesuis has better ability to survive in phagocytic cells during infection and this may explain why S. choleraesuis always dominate in cultivated rate from outbreak cases in the field.
In addition, the outbreak of classical swine fever virus (CSFV) infection is almost accompanied with salmonellosis in the field, but the mechanism and relationship between both diseases still remain unclear. The new invaded strain (Ping-Tung isolate) of CSFV was used to investigate the influence of CSFV on the clearance activity of PBP against Salmonella. The results verified that the total amounts of peripheral blood leukocytes decreased significantly to 20-30% in comparison with the control group, and both lymphocytes and monocytes were the major target cells during CSFV infection. Moreover, the phagocytic ability of neutrophils and monocytes against S. choleraesuis and S. typhimurium during CSFV infection declined at 3 and 7 days post infection (DPI) respectively, and even dropped to 20-30% at 18-21 DPI. In addition, the respiratory burst of PBP was dropped to 70-80% at 3-7 DPI and slightly recovered at 10-14 DPI, however it dramatically dropped to 10-30% at 18-21 DPI. These results suggest that CSFV infection not only induces leucopenia but also impairs the phagocytic and respiratory burst activity of PBP against Salmonella spp. in swine.
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