In vitro activity of the chelating agents nitroxoline and oxine against Mycobacterium bovis BCG

The chelating antibiotic nitroxoline (5-nitro-8-hydroxyquinoline) showed a bacteriostatic effect at a concentration of 10 microM for Mycobacterium bovis BCG. At higher concentrations the compound showed moderate cidal activity against growing bacilli. In contrast, its non-nitrated derivative oxine (8-hydroxyquinoline, MIC=2 microM) reduced the viability of a growing culture rapidly, 5000-fold at a concentration where the nitroxoline was merely bacteriostatic. Both compounds showed appreciable cidal activity against bacilli in their hypoxic dormant state.