Effect of amoxycillin and clavulanic acid, alone and in combination, on human polymorphonuclear leukocyte function against Staphylococcus aureus.

The effect of amoxycillin and clavulanic acid on the interaction in vitro of human polymorphonuclear leukocytes with Staphylococcus aureus was examined. The exposure of a non-penicillinase producing Staphylococcus aureus strain to one-fourth the MIC of amoxycillin or clavulanic acid alone significantly increased the uptake of both unopsonized and opsonized bacteria by human polymorphonuclear leukocytes. This effect was also observed when bacteria were exposed to one-fourth the MIC of different proportions of the combination of amoxycillin and clavulanic acid (4/1, 1/1, 1/8 and 1/32). When a penicillinase-producing Staphylococcus aureus strain was used, only clavulanic acid significantly increased the uptake of unopsonized bacteria. The production of superoxide radicals by human polymorphonuclear leukocytes was impaired only by the presence of high concentrations (100 mg/l) of both clavulanic acid or the combination amoxycillin/clavulanic acid (4/1). At this high concentration, however, amoxycillin/clavulanic acid (4/1) significantly increased the intracellular killing of Staphylococcus aureus.