Optimization of basic conditions for phagocytosis assay. Different quantities of FITC-labelled bacteria (A) and different incubation times of phagocytosis (B) were tested with PAM and virulent (solid lines) or non-virulent (dashed lines) strains. Results are shown as the percentage of macrophages with green-fluorescent bacteria detected by flow cytometry. The strains used were Nagasaki (●), 264/99 (■), SW114 (○) and F9 (□). In (B), bacterial inoculi were 5 × 10⁸ CFU of Nagasaki, 2 × 10⁸ CFU of 264/99, 2 × 10⁷ CFU of SW114 and 2 × 10⁷ CFU of F9.