The in-vitro activity of clarithromycin and other macrolides against the type strain of Chlamydia pneumoniae (TWAR).

The activity of oxytetracycline and seven macrolide antibiotics was investigated against a prototype strain of Chlamydia pneumoniae in cell culture. Following incubation, inoculated cell monolayers were fixed in methanol and stained with a genus specific immunofluorescent monoclonal antibody before examination for inhibition of inclusion formation. The most active agent was clarithromycin (MIC 0.007 mg/l), followed by erythromycin (0.06 mg/l). Other macrolides were less active; josamycin and roxithromycin (0.25 mg/l), midecamycin acetate and azithromycin (0.5 mg/l) and spiramycin (4.0 mg/l). The MIC of oxytetracycline was 0.25 mg/l. Clinical evaluation of clarithromycin for C. pneumoniae lower respiratory infection is indicated.