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Evaluation of bacteriologic culture of pooled fecal samples for detection of Mycobacterium paratuberculosis

Scott J. WellsCollege of Veterinary Medicine, Department of Clinical and Population Sciences, University of Minnesota, St Paul, MN 55108-1004.

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Robert H. WhitlockDepartment of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348.

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Cynthia J. LindemanCollege of Veterinary Medicine, Department of Clinical and Population Sciences, University of Minnesota, St Paul, MN 55108-1004.
Present address is Pharmacia Animal Health,7000 Portage Rd, Kalamazoo, MI 49001-0199.

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Terry FyockDepartment of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348.

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Abstract

Objective—To compare sensitivity of several methods of bacteriologic culture of pooled bovine fecal samples for detection of Mycobacterium paratuberculosis and evaluate homogeneity in number of M paratuberculosisin pooled fecal samples.

Sample Population—Feces from 10 dairy cows that shed M paratuberculosis at various concentrations and 1 dairy cow known to be free of infection with M paratuberculosis.

Procedure—5 fecal pooling methods, 2 culture methods, and 2 pool sizes were evaluated. Each pooled sample contained 1 infected sample and 4 or 9 uninfected samples.

Results—Sensitivity of detection of M paratuberculosis was greater with smaller pool size (5 vs 10 samples/ pool). Detection sensitivity was also associated with concentration of bacteria in the infected sample. Results indicated that, compared with concurrent bacterial culture of individual infected samples, 37 to 44% of pooled samples with low bacterial concentrations yielded positive culture results and 94% of pooled samples with high bacterial concentrations yielded positive results.

Conclusions and Clinical Relevance—Bacteriologic culture of pooled fecal samples may provide a valid and cost-effective method of detecting M paratuberculosis infection in cattle herds. (Am J Vet Res 2002;63:1207–1211)

Abstract

Objective—To compare sensitivity of several methods of bacteriologic culture of pooled bovine fecal samples for detection of Mycobacterium paratuberculosis and evaluate homogeneity in number of M paratuberculosisin pooled fecal samples.

Sample Population—Feces from 10 dairy cows that shed M paratuberculosis at various concentrations and 1 dairy cow known to be free of infection with M paratuberculosis.

Procedure—5 fecal pooling methods, 2 culture methods, and 2 pool sizes were evaluated. Each pooled sample contained 1 infected sample and 4 or 9 uninfected samples.

Results—Sensitivity of detection of M paratuberculosis was greater with smaller pool size (5 vs 10 samples/ pool). Detection sensitivity was also associated with concentration of bacteria in the infected sample. Results indicated that, compared with concurrent bacterial culture of individual infected samples, 37 to 44% of pooled samples with low bacterial concentrations yielded positive culture results and 94% of pooled samples with high bacterial concentrations yielded positive results.

Conclusions and Clinical Relevance—Bacteriologic culture of pooled fecal samples may provide a valid and cost-effective method of detecting M paratuberculosis infection in cattle herds. (Am J Vet Res 2002;63:1207–1211)