In this study lactating female rabbits and strains of coliforms previously isolated from the cases of acute and chronic mastitis in dairy cattle were employed.
The pathological changes were observed on the mastitis experimentally induced with the coliform strains and the mamary glands after infusions of E. coli suspension together with dexamethasone, dextran iron or transferrin were grossly and microscopically observed. From the results reported, the following points are concluded.
In the bacterial suspension-infused groups by E. coli, K. pneumoniae and Ent. aerogenes, respectively, the affected quarters of udder showed grossly sweilling, hyperemia, hemorrhage, focal necrosis and firmness.
The microscopic findings of early stage of the mastitis were appearance of large numbers of heterophils in the glandular lumina and ducts accompanied by degeneration, necrosis and desquamation of epithelial cells and also infiltration of heterophils, hemorrhage and edema in the interstitial tissue and destruction of alveoli. Later, proliferation of fibroblasts, plasma cells, lymphocytes, eosinophils and macrophages appeared in the glandular tissue and with these cells necrotic foci of glandular tissue frere currounded by highly proliferated connective tissue. In addition, granulomatous inflammatory changes could be observed in the glandular tissue from the 7th day after infusion.
The difference of the inflammatory response among the groups did not recognized.
In the groups infused with dexamethasone and E. coli suspension the inflammatory response was slighter at the inflammatory change with alveolar destruction and hemorrhage was more rapid and severer than E. coli alone.
Also in the groups infused with dextran iron and E. coli suspension the inflammatory change was more rapid and severer than E. coli alone and the histological changes were not recognized in the groups infused with dextran iron alone. Reaction of the iron staining was diffusely strong positive within the glandular alveolar lumina in the groups of dextran iron alone, hut was slightly positive toward epithelial cells in the groups of dextran iron and E. coli infusion.
In the group infused with transferrin and E. coli suspension, the inflammatory response was tighter, but the peroxidase activity of the heterophils in the glandular lumina wars more or less stronger than E. coli alone.
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