In vitro activity of the novel ketolide HMR 3647 and comparative oral antibiotics against Canadian respiratory tract isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis.

The in vitro activities of HMR 3647, erythromycin A, clarithromycin, azithromycin, roxithromycin, penicillin G, ampicillin, cefuroxime, trimethoprim/sulfamethoxazole, tetracycline, ciprofloxacin, and levofloxacin were determined for 1179 Streptococcus pneumoniae, 1438 Haemophilus influenzae, and 428 Moraxella catarrhalis isolated from respiratory tract specimens by 18 medical centers across Canada during 1997-1998. On a per weight basis, HMR 3647 was the most active agent tested against S. pneumoniae with MIC90s of < or = 0.12 microgram/mL for both penicillin susceptible and penicillin intermediate isolates and 0.25 microgram/mL for penicillin-resistant isolates. HMR 3647 was also highly active against M. catarrhalis (MIC90, < or = 0.12 microgram/mL), but less active against H. influenzae (MIC90, 4 micrograms/mL).