[Influence of antibiotics on the phagocytosis of Klebsiella pneumoniae by alveolar macrophages (author's transl)].

The effect of gentamicin and cephalothin on the phagocytosis of Klebsiella pneumoniae by alveolar macrophages of guinea pigs was tested. At their minimal bactericidal concentration (MBC) the antibiotics did not influence the uptake of bacteria by macrophages in the presence of various antibody titers. As expected, the number of surviving bacteria after intracellular ingestion decreased at MBC of the antibiotics. The uptake of bacteria was inhibited by very high concentrations of gentamicin and cephalothin only. The intracellular killing of the bacteria was already higher in the presence of relatively low antibiotic concentrations (one third of the minimal inhibitory concentration, MIC) as compared to the killing without antibiotics. Above this levels, even if they were considerably higher than the MIC, the antibiotics had no additional effect on the number of bacteria surviving after ingestion. These findings indicate that concentrations above one third of the MIC of gentamicin or cephalothin are not necessarily of advantage for the effect of macrophages on the bacteria, provided that sufficient levels of antibodies are also present.