Antimicrobial Activity of Gallium Nitrate against Mycobacterium avium subsp. paratuberculosis in Neonatal Calves

• Published in: Journal of veterinary internal medicine 2011-09, Vol.25 (5), p.1152-1155
• Main Authors: Fecteau, M.-E., Whitlock, R.H., Fyock, T.L., McAdams, S.C., Boston, R.C., Sweeney, R.W.
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn - microbiology; Anti-Bacterial Agents - therapeutic use; Cattle; Cattle Diseases - drug therapy; Cattle Diseases - microbiology; Feces - microbiology; Gallium - therapeutic use; Johne's disease; Male; Mycobacterium avium; Mycobacterium avium subsp. paratuberculosis - drug effects; Paratuberculosis; Paratuberculosis - drug therapy; Prophylaxis
• ISSN: 0891-6640; 1939-1676; 1939-1676
• DOI: 10.1111/j.1939-1676.2011.0768.x

Background: Mycobacterium avium subsp. paratuberculosis (MAP), the agent of Johne's disease in cattle, is a facultative intracellular bacterium that is dependent on ferric iron for its survival and replication. Gallium (Ga), a trivalent semimetal that shares many similarities with ferric iron and functions as an iron mimic has been shown to have in vitro antimicrobial activity against several microorganisms, including MAP. Objectives: (1) To investigate the antimicrobial activity of Ga in calves experimentally infected with MAP; and (2) to monitor for potential adverse effects of Ga on calf health. Animals: Twelve Holstein calves. Methods: Randomized blind controlled experiment. Beginning at 10 days of age (study day 1), the experimental calves (n = 6) were treated with 20 mg/kg gallium nitrate daily for 45 days. On study days 4 and 5, all calves were challenged with a PO dose of a live field strain MAP. Treated calves were monitored daily for adverse effects. Calves were euthanized on study day 100, and 29 tissue samples and 1 fecal sample were collected from each calf. Samples were cultured for MAP by MGIT liquid culture system, Herrold's Egg Yolk Medium culture, or both. Results: No adverse effects were observed in the treated calves. Treatment was associated with a significant reduction in MAP tissue burden when compared with control calves (P = .017). Conclusions and Clinical Relevance: Chemoprophylactic treatment of calves with Ga before and during the period of high susceptibility decreased MAP tissue colonization in experimentally infected neonatal calves.