Activity of HMR 3647 Compared to Those of Five Agents against Haemophilus influenzae and Moraxella catarrhalis by MIC Determination and Time-Kill Assay

The microdilution MICs of HMR 3647, erythromycin A, azithromycin, clarithromycin, roxithromycin, and pristinamycin against 50/90% of 249 Haemophilus influenzae and 50 Moraxella catarrhalis isolates were 2/4, 0.06/0.125; 8/16, 0.25/0.25; 2/4, 0.06/0.125; 16/16, 0.25/0.25; 32/>32, 1/2; and 2/4, 0.5/0.5 μg/ml. Azithromycin was bactericidal against all 10 H. influenzae and 3 of 5 M. catarrhalis isolates and HMR 3647, erythromycin A, clarithromycin, roxithromycin, and pristinamycin were bacteriostatic, against all 15 strains after 24 h at the MIC.