Rhodococcus equi, a facultative intracellular bacterium, causes severe
pneumonia in foals. Evidence suggests that most foals become infected very early in life, when they have immature or ineffective innate immune responses. This study evaluated the antimicrobial activity of
gallium against R. equi, as a potential chemoprophylactic and therapeutic agent. Rhodococcus equi was grown in media with various concentrations of
gallium nitrate (GN), with and without excess
iron. GN significantly inhibited growth and killed R. equi, and these effects were abolished with excess
iron. Antimicrobial effects of Ga appear to be related to its interference with
iron metabolism. Mice were treated orally with
gallium maltolate (GaM), 10 or 50 mg/kg BW, or distilled H2O prior to and after experimental
infection with R. equi. Six days post-
infection, organs were harvested and R. equi concentrations assessed, and serum
gallium concentrations determined. GaM was absorbed in a dose-dependent manner, and R. equi tissue burdens were greater in control mice than in all GaM-treated mice. GaM may aid in the control of disease by preventing development of overwhelming R. equi tissue burdens prior to the establishment of requisite innate and adaptive immune responses.