In vitro antimicrobial activity of gallium maltolate against virulent Rhodococcus equi.

Abstract The objective of this study was to determine the in vitro antimicrobial activity of gallium maltolate (GaM) against Rhodococcus equi . A total of 98 virulent bacterial isolates from equine clinical cases were examined, of which 19 isolates were known to be resistant to macrolides and rifampin. Isolates were cultured with various concentrations of GaM and minimal inhibitory concentration (MIC) values were determined after 24 and 48 h. Both the MIC 50 and the MIC 90 after 24 h of growth were 3,560 ng/mL (8 μM) and after 48 h of growth were 14,241 ng/mL (32 μM). There were no apparent differences between MICs of macrolide-resistant and macrolide-susceptible isolates.