Comparative study on the macrolides erythromycin and clarithromycin: antibacterial activity and influence on immune responses.

The in vitro activity of erythromycin and clarithromycin (a new macrolide antibiotic) on clinical bacterial isolates as well as their effects on the cellular and humoral immune responses in BALB/c-mice and on human granulocytes/monocytes was investigated. Treatment of BALB/c-mice for 7 days with these drugs did not influence the delayed type hypersensitivity to oxazolone nor the production of IgG and IgM immunoglobulins. In vitro, exposure of granulocytes to erythromycin resulted in increased phagocytosis only in higher concentrations (20 mcg/ml), whereas clarithromycin enhanced chemiluminescence response of granulocytes in concentrations ranging from 2.5-20 mcg/ml. Subinhibitory concentrations of both substances modified Staphylococcus aureus and made them more susceptible for granulocyte phagocytosis.