Activity of antibiotics against microorganisms ingested by mononuclear phagocytes.

The data available on the activity of antibiotics against microorganisms ingested by mononuclear phagocytes are reviewed. The antibacterial activity of penicillins against Staphylococcus aureus is enhanced by human monocytes. This enhancement is possibly brought about by a peptidoglycan-degrading enzyme that is produced and secreted by monocytes. Aminoglycosides affect bacteria ingested by mononuclear phagocytes, but their intracellular activity is limited as compared with that of non-phagocytosed bacteria. Clindamycin, erythromycin, ciprofloxacin and rifampicin are effective against intracellular bacteria. The first three of these antibiotics do not show enhanced activity against phagocytosed bacteria, contrary to what might be expected from their high cell-associated concentrations.