SUSCEPTIBILITIES TO CLARITHROMYCIN AND ERYTHROMYCIN OF ISOLATES OF CHLAMYDIA-PNEUMONIAE FROM CHILDREN WITH PNEUMONIA

We tested in vitro 49 isolates of Chlamydia pneumoniae obtained from 3 5 children with community-acquired pneumonia against clarithromycin an d erythromycin. The children were part of a treatment study comparing the two drugs. Clarithromycin was 2- to 10-fold more active than eryth romycin, with a MIC for 90% of strains tested and minimal chlamydiacid al concentration for 90% of strains tested of 0.031 mu g/ml compared w ith 0.125 mu g/ml for erythromycin. Eight of these children, two of wh om were treated with erythromycin and six of whom received clarithromy cin, remained culture positive after treatment. We were able to test 2 1 isolates from these children. All were susceptible to both drugs, an d the MICs did not change after therapy.