FITC was prepared at a final concentration of 1 mg/ml in 50 mM carbonate, 150 mM NaCl buffer (pH 9.2). Bacteria were collected in 1 ml PBS/Mg/Ca and re-suspended by gently pipetting and pelleted at 3000 rpm for 3 min. After removal of the supernatant, the bacteria were re-suspended in 500 ml of FITC solution and incubated at room temperature with gentle shaking in the dark for 30 min. After washing (56) the bacteria were resuspended in PBS/Mg/Ca with 1% BSA to quench remaining FITC. The labeled bacteria were diluted to a working ratio of 30 bacteria to 1 neutrophil.