FIG 4.

P. aeruginosa survival after exposure to neutrophil extracellular traps. A total of 1 × 10⁷ CFU of P. aeruginosa bacteria were incubated with PMA-treated neutrophils (MOI of 10:1), and bacterial viability was determined by direct plate counts (CFU per milliliter) before and after 4 h of incubation with NETs. Bacterial counts were normalized to counts in the absence of neutrophils. DNase I was added exogenously 30 min prior to the end of the experiment to degrade NETs and ensure accurate counts of recoverable colonies. Data are presented as the average percentages of bacterial survival, and error bars represent the standard deviations from 6 replicates (n = 3). (A) Wild-type PAO1 survival compared to that of the xcpU::lux type II secretion mutant. Significant differences were determined by using the unpaired t test (****, P < 0.0001). (B) Bacterial survival of wild-type PAO1 and the eddAB double mutant, which was complemented with pEddA or pEddB. Significant differences compared to the double mutant were determined by one-way ANOVA with Bonferroni posttests (****, P < 0.0001).