Isolation of Mycobacterium paratuberculosis after oral inoculation in uninfected cattle

Raymond W. Sweeney From the Department of Clinical Studies and Department of Pathobiology (Hamir), New Bolton Center, University of Pennsylvania, School of Veterinary Medicine, Kennett Square, PA 19348.

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Robert H. Whitlock From the Department of Clinical Studies and Department of Pathobiology (Hamir), New Bolton Center, University of Pennsylvania, School of Veterinary Medicine, Kennett Square, PA 19348.

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Amir N. Hamir From the Department of Clinical Studies and Department of Pathobiology (Hamir), New Bolton Center, University of Pennsylvania, School of Veterinary Medicine, Kennett Square, PA 19348.

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Anne E. Rosenberger From the Department of Clinical Studies and Department of Pathobiology (Hamir), New Bolton Center, University of Pennsylvania, School of Veterinary Medicine, Kennett Square, PA 19348.

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Stephanie A. Herr From the Department of Clinical Studies and Department of Pathobiology (Hamir), New Bolton Center, University of Pennsylvania, School of Veterinary Medicine, Kennett Square, PA 19348.

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Summary

Feces from cows naturally infected with Mycobacterium paratuberculosis was given to 6 uninfected heifers by orogastric intubation, to determine whether ingested organisms could be passively excreted and detected by bacteriologic culture of feces (ie, false-positive result). Heifers were paired, and each pair received a different dose of feces on days 1 and 2. Fecal samples were collected from the heifers 3 times daily. Mycobacterium paratuberculosis was detected in fecal samples of all heifers within 18 hours of being given the first dose of feces. The number of colony-forming units peaked on days 3 or 4, and organisms were no longer detected by day 7. The number of colony-forming units in fecal samples from the heifers was approximately proportional to the dose given. On days 15 and 16, the experiment was repeated with feces from a second infected cow. Results were similar to those in the first experiment. All heifers remained seronegative (agar-gel immunodiffusion test and elisa) and had negative results to the intradermal johnin test throughout the experiment.

Lymph node and intestinal tissues were obtained from all 6 heifers at slaughter on day 28. Mycobacterium paratuberculosis was not isolated from mesenteric lymph nodes from the ileocecal valve region, but was isolated from ileal mucosal samples from each heifer.

Summary

Feces from cows naturally infected with Mycobacterium paratuberculosis was given to 6 uninfected heifers by orogastric intubation, to determine whether ingested organisms could be passively excreted and detected by bacteriologic culture of feces (ie, false-positive result). Heifers were paired, and each pair received a different dose of feces on days 1 and 2. Fecal samples were collected from the heifers 3 times daily. Mycobacterium paratuberculosis was detected in fecal samples of all heifers within 18 hours of being given the first dose of feces. The number of colony-forming units peaked on days 3 or 4, and organisms were no longer detected by day 7. The number of colony-forming units in fecal samples from the heifers was approximately proportional to the dose given. On days 15 and 16, the experiment was repeated with feces from a second infected cow. Results were similar to those in the first experiment. All heifers remained seronegative (agar-gel immunodiffusion test and elisa) and had negative results to the intradermal johnin test throughout the experiment.

Lymph node and intestinal tissues were obtained from all 6 heifers at slaughter on day 28. Mycobacterium paratuberculosis was not isolated from mesenteric lymph nodes from the ileocecal valve region, but was isolated from ileal mucosal samples from each heifer.

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