The in-vitro activity of HMR 3647, a new ketolide antimicrobial agent

The in-vitro activity of HMR 3647, a novel ketolide, was investigated in co mparison with those of erythromycin A, roxithromycin, clarithromycin (14-me mbered ring macrolides), amoxycillin-clavulanate and ciprofloxacin against 719 recent clinical Gram-positive, Gramnegative and anaerobic isolates and type cultures. HMR 3647 generally demonstrated greater activity than the ot her compounds with MIC(90)s of less than or equal to 0.5 mg/L, except for S taphylococcus epidermidis (MIC90 128 mg/L), Haemophilus influenzae (MIC90 = 2 mg/L), Enterococcus faecalis (MIC90 = 2 mg/L), Enterococcus faecium (MIC 90 = 1 mg/L) and the anaerobes, Bacteroides fragilis (MIC90 = 2 mg/L) and C lostridium difficile (MIC90 = 1 mg/L). In general, an increase in the size of the inoculum from 10(4) to 10(6) cfu On selected strains had little effe ct on the MICs of HMR 3647. Additionally, the in-vitro activity of HMR 3647 was not affected by the presence of either 20 or 70% (v/v) human serum. Th e antichlamydial activity of HMR 3647 was generally greater than that of co mmonly used antichlamydial antimicrobials.