Defective neutrophil oxidative burst in preterm newborns on exposure to coagulase-negative staphylococci

The neutrophil oxidative burst is a product of the regulated assembly of the multicomponent oxidase enzyme. Our aim was to compare the oxidative burst in term (n = 10) and preterm newborns <31 wk gestational age (n = 10) after stimulation with coagulase-negative staphylococci in vitro. Strains of Streptococcus epidermidis with different invasive and slime-producing properties, one strain of S. haemolyticus, and one strain of group B-streptococcus were investigated. A whole-blood flow cytometric assay using the oxidation of hydroethidine to ethidium bromide was used. The oxidative activity in unstimulated neutrophil granulocytes [polymorphonuclear leukocytes (PMNLs)] was similar in term and preterm newborns, but the preterm newborns showed a significantly lower capacity to up-regulate the oxidative burst intensity after bacterial stimulation (p = 0.004). In the term but not in the preterm group, the oxidative burst intensity after bacterial stimulation correlated with the baseline oxidative burst intensity. After bacterial stimulation, there was a trend toward a greater percentage of activated neutrophils in the term group than in the preterm group, but the difference was less pronounced than that in oxidative burst intensity. Significant differences in oxidative burst response to different bacterial strains were observed (p < 0.001), but the differences could not be correlated exclusively to invasive capacity or slime-producing properties. It is concluded that the baseline oxidative activity is similar in term and preterm PMNLs but that preterm PMNLs have a decreased capacity to increase the oxidative burst in response to bacterial stimulation.