[Comparative study of intramacrophagic penetration and action on phagocytosis of a macrolide (spiramycin) and a fluoroquinolone (pefloxacin)].

Antibiotic-phagocyte interaction is an important parameter involved in the elimination process of intracellular bacteria. The aim of the present study was to compare, using the same model, the phagocytic uptake and the intracellular activity of a macrolide and a quinolone. Accumulation of spiramycin and pefloxacin by guinea pig peritoneal macrophages (GPpM) was studied by means of a velocity-gradient centrifugation technique and expression of the ratio of the cellular concentration of antibiotic to the extracellular concentration (IC-EC). Three aspects of Staphylococcus aureus (209-P) phagocytosis were studied: 1) the phagocytic capacity (PC), mean number of ingested cocci by GpPM; 2) the phagocytic activity (PA), percentage of phagocyting GpPM with at least one bacterium; 3) the number of intracellular viable bacteria (IVB). Phagocytic capacity and phagocytic activity were determined by fluorescence microscopy using S. aureus stained with acridine orange. Intracellular viable bacteria were quantified by standard colony counts (CFU). The ratios of intracellular to extracellular concentration of pefloxacin and spiramycin are respectively 9 and 23. Pretreatment of guinea-pig peritoneal macrophages with 10 mg/l of each antibiotic does not modify phagocytic capacity and phagocytic activity, but lead to a decrease of intracellular viable bacteria. S. aureus pretreatment with 1/4 the MIC of each antibiotic increased phagocytic capacity and phagocytic activity and decrease intracellular viable bacteria (especially spiramycin).(ABSTRACT TRUNCATED AT 250 WORDS)