FIG. 2.

Half times for killing of A. actinomycetemcomitans by PMNs and ciprofloxacin. In these experiments, the indicated CFU were added to tubes containing 4 × 10⁶ PMNs or 0.5 μg of ciprofloxacin/ml. Half times for bacterial killing were calculated from the numbers of CFU recovered after 30 min. The data are presented as the means ± SEM of three separate experiments. Within each group of bars, significant treatment effects were observed (P < 0.03; repeated measurement by analysis of variance). At lower ratios of bacteria to PMNs (in a solution containing 1.2 × 10⁷ or 4 × 10⁷ CFU), the half time for killing by control or ciprofloxacin-loaded PMNs was significantly shorter than by ciprofloxacin alone (P < 0.05; Tukey's test). At a ratio of 30:1, the half time for killing by ciprofloxacin-loaded PMNs was significantly shorter than that produced by control PMNs or ciprofloxacin alone (P < 0.05). At a ratio of 90:1, the half time for killing by ciprofloxacin alone or by ciprofloxacin-loaded PMNs was significantly shorter than that produced by control PMNs (P < 0.05).