Uptake of fluoroquinolones in human monocytes isolated from peripheral blood

The aim of this study was to develop a technique for separating monocytic c ells in suspension from peripheral blood to measure the intracellular penet ration of three fluoroquinolones (ofloxacin, ciprofloxacin and sparfloxacin ). Mononucleated cells were isolated from the blood on a density gradient with lymphoprep and purified by a specific technique of adhesion and disadhesio n on fibronectin. The monocytes were obtained in suspension with 76.8% puri ty and 97.9% viability. This was a convenient form for measurement of intra cellular accumulation by use of the velocity-centrifugation technique. Intr a-monocytic penetration of ciprofloxacin, ofloxacin and sparfloxacin was me asured at equilibrium after 30-min incubation in the presence of 16 mu g mL (-1) antibiotic. The results revealed low intra-monocytic accumulation of c iprofloxacin (intracellular-extracellular = 1.76) and ofloxacin (intracellu lar-extracellular = 1.42). The penetration of sparfloxacin was significantl y higher (intracellular-extracellular = 2.4). This study confirms the important differences between human immunocompetent cells in terms of their ability to concentrate quinolones. It also underli nes the importance of monocyte-macrophage cellular differentiation as a det erminant of antibiotic penetration.