FIG 4.

Deletion of lpxO increases human phagocyte-mediated killing of A. baumannii. Three hundred μl of fresh human blood (from three different donors) was mixed with 1 × 10⁷ CFU of A. baumannii ATCC 17978, A. baumannii ΔlpxO mutant (ΔlpxO), and A. baumannii ΔlpxO::Tn7lpxO mutant (ΔlpxO::Tn7lpxO) and incubated at 37°C for 3 h. The bacterial counts recovered were then divided by the initial counts. Experiments were performed with duplicate samples on three independent occasions. *, P < 0.05 versus A. baumannii ATCC 17978, determined using one-way ANOVA with Bonferroni contrasts; n.s., not significant.