- johnin reaction
- a skin reaction like the tuberculin reaction, produced by filtrates of cultures of Mycobacterium avium subsp. paratuberculosis> (see johnin); used in the diagnosis of Johne disease in cattle.
Medical dictionary. 2011.
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johnin — A product used as a diagnostic agent, analogous to tuberculin but made from Mycobacterium paratuberculosis (the causative organism of Johne disease) grown in a broth medium containing Mycobacterium phlei (timothy hay bacillus); used as an… … Medical dictionary