title: Interaction between human monocytes and penicillin G in relation to the antibacterial effect on Staphylococcus aureus.
abstract: The influence of the presence of monocytes on the effect of penicillin G on Staphylococcus aureus was studied. Conditions were varied in such a way that phagocytosis and intracellular killing of S. aureus by monocytes did not occur, was short lasting and limited, or long lasting and extensive. Synergism between penicillin G and monocytes was observed in the absence of and during limited phagocytosis and intracellular killing by the monocytes. When phagocytosis and intracellular killing were optimal, addition or antagonism between penicillin G and monocytes was observed. Enhancement of the antibacterial effect of penicillin G was also obtained in the presence of monocyte supernatant (the cell-free medium in which monocytes had been incubated for 3 hr). This indicates that monocytes secrete a factor that enhances the antibacterial activity of penicillin G. Serum inhibits the activity of this factor.
mesh_terms: D000328:Adult; D001770:Blood Bactericidal Activity; D006801:Humans; D009000:Monocytes / Q000382:microbiology / Q000502:physiology*; D009895:Opsonin Proteins; D010400:Penicillin G / Q000494:pharmacology*; D010587:Phagocytosis; D013211:Staphylococcus aureus / Q000187:drug effects / Q000276:immunology / Q000502:physiology*
chemical_list: D009895:Opsonin Proteins; D010400:Penicillin G