Differential involvement of reactive oxygen species and myeloperoxidase in oxygen-dependent killing of urinary tract bacterial isolates by polymorphonuclear leukocytes.

Abstract

We examined the involvement of reactive oxygen species (ROS) and myeloperoxidase (MPO) in bacterial killing by human polymorphonuclear leukocytes (PMN) by means of a chemiluminescence assay. Using four bacterial strains, including Pseudomonas aeruginosa strain ATCC 27853 and three other strains of P. aeruginosa that were isolated from patients with urinary tract infections, we examined whether the production of ROS and changes in MPO activity altered the numbers of bacteria in contact with PMN. For three strains (P. aeruginosa strain ATCC 27853, strain 40, and strain 64), a decrease in number of viable bacteria was observed with PMN addition over three 20-min intervals that differed significantly from observations in these strains without the addition of PMN, and residual MPO activity of these three strains correlated significantly with decreases in numbers of viable bacteria. We concluded that MPO-dependent processes are strongly favored by human PMN for the oxidative killing of bacteria.