IN-VITRO AND IN-VIVO ACTIVITIES OF MACROLIDES AGAINST MYCOPLASMA-PNEUMONIAE

We investigated the in vitro and in vivo activities of macrolides agai nst Mycoplasma pneumoniae. In vitro MICs of azithromycin, erythromycin , clarithromycin, and roxithromycin were determined. Azithromycin was the most potent antimicrobial agent tested in vitro. Its MIC for 90% o f the strains was 0.00024 mug/ml. MICs for 90% of the strains of eryth romycin, clarithromycin, and roxithromycin were 0.0156, 0.0078, and 0. 03125 mug/ml, respectively. In vivo activities were assessed in a pulm onary infection model with Syrian golden hamsters. We evaluated the in vivo effects on reduction of viable M. pneumoniae cell counts and on reduction of microscopic and macroscopic histopathologies for azithrom ycin, erythromycin, and clarithromycin given at 10 mg/kg once daily fo r 1 and 3 days and given at 15 mg/kg twice daily for 2.5 and 5 days. A zithromycin was significantly more effective than erythromycin or clar ithromycin in the same regimens. Especially at 10 mg/kg once daily for 1 day, only azithromycin was significantly effective in the reduction of viable M. pneumoniae cells and histopathologies. These results sho w that azithromycin is more efficacious than the other drugs tested ag ainst M. pneumoniae pneumonia in hamsters. These data suggest that cli nical studies of macrolides in human patients are warranted.