Recently, we reported rifabutin hyper-activity againstAcinetobacter baumannii. We sought to characterize if any additional rifamycins (n = 22) would also display hyper-activity when tested in iron-limited media againstA.baumannii,K.pneumoniae, andE.coli. MICs were determined against representative clinical isolates using the iron-limited media RPMI-1640. Only rifabutin was hyperactive againstA.baumannii.