IN-VITRO ACTIVITY OF MACROLIDES AGAINST INTRACELLULAR LEGIONELLA-PNEUMOPHILA

The antibacterial effects of clarithromycin, azithromycin, and erythro mycin were determined against five strains of Legionella pneumophila i ncluding L. pneumophila ATCC 33823 and four clinical isolates. Extrace llular minimum inhibitory concentrations (MICs) and MBCs were determin ed by a microdilution method. Clarithromycin was the most active drug (MIC less than or equal to 0.015-0.06), followed by azithromycin (MIC 0.03-0,12) and erythromycin (MIC 0.06-0.02). The antibacterial effect of these macrolides was then determined against L. pneumophila grown i ntracellularly in MRC-5 human fetal lung fibroblast cells. At two and eight times the extracellular MBC, erythromycin, azithromycin, and cla rithromycin were equally effective in inhibiting growth of these five strains of intracellular L. pneumophila. (C) 1996 Elsevier Science Inc .