STUDIES ON THE PATHOGENESIS OF SALMONELLA HEIDELBERG, SALMONELLA TYPHIMURIUM AND SALMONELLA CHOLERAESUIS VAR. KUNZENDORF INFECTION IN WEANLING PIGS
Abstract
These studies were conducted to define the pathogenic potential of Salmonella heidelberg for weaned pigs and to compare the clinical and pathological manifestations of infection with Salmonella heidelberg to those observed with infection by Salmonella typhimurium and Salmonella choleraesuis var. kunzendorf. Oral inoculation of pigs with S. heidelberg resulted in marked catarrhal enterocolitis with secretion of large amounts of fluid in the small intestines and colon followed by the development of a persistent carrier state. With fluorescent antibody and microbiological culture techniques, S. heidelberg was demonstrated to colonize principally the ileum, invade ileal mucosal epithelium and reach mesenteric lymph nodes and extra-intestinal tissues by 8 hours. Microscopic lesions were confined to the gastrointestinal tract, involved the ileum most severely and were characterized as diffuse atrophic enteritis. Serum agglutinins to S. heidelberg were first detected 10 days post exposure. Reinoculation 30 days from the initial exposure failed to elicit clinical disease, however a rapid anamnestic serologic response occurred. Infection with S. typhimurium resulted in acute enterocolitis of variable severity, whereas infection with S. choleraesuis var. kunzendorf resulted initially in acute septicemia with development of diarrhea after 72 hours. The intestinal lesions of both S. typhimurium and S. choleraesuis var. kunzendorf were characterized by necrosis of surface and cryptal enterocytes frequently associated with thrombosis of venules and arterioles of the lamina propria and submucosa. The intestinal lesions of S. choleraesuis var. kunzendorf were more severe and developed into large necrotic and ulcerative areas in the colonic mucosa. The most consistent systemic lesion of S. choleraesuis var. kunzendorf infection was hematogenous interstitial pneumonia and multifocal hepatic necrosis. S. heidelberg, S. typhimurim and S. choleraesuis var. kunzendorf were demonstrated ultrastructurally within enterocytes of ligated ileal loops, however actual penetration was not observed. Intracellular bacteria were morphologically intact, occurred free and membrane bound with equal frequency and caused no detectable cytotoxic effect to the cell.
Degree
Ph.D.
Subject Area
Veterinary services
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