In vitro activities of azithromycin, clarithromycin, erythromycin, and tetracycline against 13 strains of Chlamydia pneumoniae

Thirteen strains of Chlamydia pneumoniae were evaluated for their in vitro susceptibilities to azithromycin, clarithromycin, erythromycin, and tetracycline. The MIC ranges were 0.125 to 0.5 mu g/ml for azithromycin, 0.031 to 1.0 mu g/ml for clarithromycin, 0.125 to 1.0 mu g/ml for erythromycin, and 0.125 to 1.0 mu g/ml for tetracycline, The ranges for the minimal lethal concentrations were 0.125 to 0.5 mu g/ml for azithromycin. 0.031 to 1.0 mu g/ml for clarithromycin, 0.125 to 1.0 mu g/ml for erythromycin, and 0.25 to 1.0 mu g/ml for tetracycline. Clarithromycin and azithromycin were the most active antibiotics against C. pneumoniae in vitro.