MICs of rifampin, clarithromycin, and azithromycin, each in the presence and absence of SPR741, against E. coli ATCC 25922, K. pneumoniae ATCC 43816, and A. baumannii NCTC 12156

AntibioticStrainMIC (μg/ml) with SPR741 at concn (μg/ml) of:Potentiation factora at 8 μg/ml SPR741FICI
Rifampin E. coli ATCC 25922160.0080.0040.0028,1920.06–0.25
K. pneumoniae ATCC 4381616210.5320.06–0.13
A. baumannii NCTC 1215620.50.250.06320.09–0.27
Clarithromycin E. coli ATCC 25922640.060.030.0164,0960.03–0.13
K. pneumoniae ATCC 438166464641640.05
A. baumannii NCTC 1215616410.25640.08–0.27
Azithromycin E. coli ATCC 2592220.060.060.06320.06–0.16
K. pneumoniae ATCC 4381620.060.060.06320.06
A. baumannii NCTC 121560.–0.49
  • a Fold reduction in the MIC in the presence of 8 μg/ml SPR741 relative to the MIC in the absence of SPR741.