A NEW MODEL EXAMINING INTRACELLULAR AND EXTRACELLULAR ACTIVITY OF AMOXICILLIN, AZITHROMYCIN, AND CLARITHROMYCIN IN INFECTED-CELLS

An in vitro infection model was created using a suspension of macropha ges, polymorphonuclear leukocytes, lymphocytes, fibroblasts, and human serum to which pathogen and antibiotic were added. Separate intracell ular and extracellular antibiotic concentrations and activity against Staphylococcus aureus and Legionella pneumophila were assessed for thr ee antimicrobial agents: amoxicillin, azithromycin and clarithromycin. Amoxicillin was found almost exclusively in extracellular fluid, wher e it was active; intracellularly, it was ineffective. Azithromycin, in contrast, was primarily concentrated and active intracellularly, with little activity in extracellular fluid. Clarithromycin was present in both compartments and possessed significant activity both intracellul arly and extracellularly.