MICROBIOLOGIC EFFICACY OF AZITHROMYCIN AND SUSCEPTIBILITIES TO AZITHROMYCIN OF ISOLATES OF CHLAMYDIA-PNEUMONIAE FROM ADULTS AND CHILDREN WITH COMMUNITY-ACQUIRED PNEUMONIA

Chlamydia pneumoniae was eradicated from the nasopharynges of 26 of 33 (78.8%) evaluable children and adults with community-acquired pneumon ia who were treated with azithromycin. We tested 55 isolates of C. pne umoniae obtained from 46 of these patients against azithromycin. The M IC at which 90% of the isolates were inhibited and the minimal chlamyd iacidal concentration at which 90% of strains tested were killed of az ithromycin for these isolates were both 0.5 mu g/ml. Seven patients re mained culture positive after treatment. The MICs of azithromycin for isolates from two patients increased fourfold after therapy. However, all the patients with persistent infection improved clinically. Furthe r studies of treatment of C. pneumoniae infection, utilizing culture, are needed both to assess efficacy and to monitor for the possible dev elopment of antibiotic resistance.