At the Johne's Testing Center, radiometric culture for M. paratuberculosis is used. Feces or tissue samples from any animal species can be cultured. Inverted OB sleeves are not accepted. The best tissue samples for isolation of M. paratuberculosis are the ileocecal junction, ileum, and lymph nodes adjacent to these parts of the intestine. Tissue samples should be collected promptly from animals being necropsied and immediately refrigerated.
Overnight mail is also acceptable.
Results of cultures done on fresh samples, promptly delivered to the laboratory, are most meaningful. If absolutely necessary however, frozen samples can be tested. An accession is all samples submitted at the same time by a single veterinarian from a single herd. Mycobacterial isolates can presumptively be identified as M. paratuberculosis at 8 weeks, however, DNA probe testing of each isolate is recommended to confirm the identification. This requires an additional 3 weeks.