Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/1996
Publication Date: N/A
Interpretive Summary: Pneumonia or Shipping fever, caused by a bacterium called Pasteurella haemolytica, is costly to ranchers, producers, and feedlot owners. Overall, estimated losses are thought to exceed 2 billion dollars annually. Not all the factors leading to the development of shipping fever pneumonia are known by scientists and veterinarians. In this study, we found that material in the serum of cattle and sheep can coat the surfaces of these bacteria. A large coating of host material was observed directly on the surface of the bacterium and assayed indirectly with laboratory tests. This would be an important factor leading to the development of disease. The coating would not only "camouflage" the bacterium inside the animal but also allow it to evade the animal's host defenses. This work, increasing our knowledge of the factors leading to the development of shipping fever pneumonia, will be of interest to veterinarians, animal health specialists, ,and other veterinary scientists.
Technical Abstract: Pasteurella haemolytica serotype A1 (bovine strain OK) was incubated in bovine subcutaneous tissue chambers in vivo and ovine strain 82-25 and bovine strain L101 were incubated for 2 h in heat-inactivated, protein G gamma globulin-depleted ovine or bovine serum in vitro to assess changes in morphology and lectin agglutination profiles. Cells, removed from chambers safter 2 h, were covered with an extensive, dense glycocalyx extending approximately 0.5 um from the cell surface. Cells, removed at 6 h, were covered with a sparse glycocalyx of fine fibers 0.2 to 0.3 um from the cell surface. Strains 82-25 and L101, incubated for 2 h in heat-inactivated ovine or bovine serum or heat-inactivated, protein G gamma globulin- depleted ovine or bovine serum were also covered with a glycocalyx. Strains 82-25 or L101, were incubated 2 h in 0.14 M NaCl with 10 mM sodium phosphate buffer, pH 7.2 with 0.5 mM CaCl2 and 0.15 mM MgCl2, buffer with 25% heat-inactivated, gamma globulin-depleted ovine serum, or buffer with 25% heat-inactivated, gamma globulin-depleted bovine serum. Agglutination profiles were then determined with 17 lectins. Profiles did vary with 7 of 17 lectins. Altered profiles indicate a change in the bacterial cell surface; possibly by absorption or alteration of surface carbohydrate moieties by serum constituents.