An in Vitro Investigation of the Intracellular Bioactivity of Amoxicillin, Clindamycin, and Erythromycin for Staphylococcus aureus

Abstract

The intraphagocytic bioactivities for Staphylococcus aureus of amoxicillin, clindamycin, and erythromycin (0.0075-20 µ/ml) were measured in human polymorphonuclear leukocytes (PMNLs) with the combination of a fluorochrome microassay and a radioassay. PMNLs with normal or depleted membrane-associated oxidative metabolism were used to investigate the interactions that may occur between the intrinsic O₂ dependent antimicrobial systems of human phagocytes and antimicrobial agents in the elimination of intracellular microbial pathogens. Neutralization of 0₂-dependent antimicrobial systems with retention of phagocytic capacity was achieved with use of PMNLs.from four children with chronic granulomatous disease (COD) or NaF-pulsed normalPMNLs. None of the test antibiotics possessed intracellular bactericidal activity. Clindamycin and erythromycin possessed significant intracellular bacteriostatic activity relativ~ to the modest activity of amoxicillin. Optimal intracellular bioactivity of all three antibiotics was obtained with normal PMNLs relative to NaF-pulsed or COD PMNLs, a result indicating the existence of beneficial interactions between the antimicrobial agents and the O₂ dependent antimicrobial systems of PMNLs.