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Antimicrobial activity of gallium nitrate against Mycobacterium avium subsp. paratuberculosis in neonatal calves
M-E Fecteau1, R H Whitlock, T L Fyock
1Department of Clinical Studies, University of Pennsylvania, Kennett Square, PA, USA. mfecteau@vet.upenn.edu
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.
Insights
Gallium (Ga) treatment reduced Mycobacterium avium subsp. paratuberculosis (MAP) tissue burden in calves without adverse effects. This study shows Ga
Area of Science:
- Veterinary microbiology
- Bacterial pathogenesis
- Antimicrobial drug development
Background:
- Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne's disease in cattle and requires iron for survival.
- Gallium (Ga), an iron mimic, exhibits in vitro antimicrobial activity against MAP.
Purpose of the Study:
- To evaluate the antimicrobial efficacy of Ga against MAP in experimentally infected calves.
- To assess the safety and potential adverse effects of Ga treatment in calves.
Main Methods:
- A randomized, blind, controlled experiment involving 12 Holstein calves.
- Calves received daily gallium nitrate (20 mg/kg) for 45 days, starting at 10 days of age.
- Calves were challenged with MAP and monitored for adverse effects; tissue and fecal samples were cultured for MAP.
Main Results:
- No adverse effects were observed in calves treated with Ga.
- Gallium treatment significantly reduced MAP tissue burden compared to control calves (P = .017).
Conclusions:
- Chemoprophylactic treatment with Ga before and during high susceptibility periods reduced MAP tissue colonization in neonatal calves.
- Gallium shows promise as a therapeutic agent for preventing or treating MAP infections in cattle.
