IN-VITRO ACTIVITY OF A NEW KETOLIDE ANTIBIOTIC, HMR-3647, AGAINST CHLAMYDIA-PNEUMONIAE

The in vitro activities of HMR 3647, roxithromycin, erythromycin, and azithromycin against 19 strains of Chlamydia pneumoniae were tested. T he MIC at which 90% of the isolates are inhibited and the minimum bact ericidal concentration at which 90% of the isolates are killed of HMR 3647 were 0.25 mu g/ml (range, 0.015 to 2 mu g/ml). Nine recently obta ined clinical isolates from children with pneumonia were more suscepti ble (MICs, 0.015 to 0.0625 mu g/ml) than older strains that had been p assaged more extensively.