Direct and phagocyte-mediated lipid peroxidation of lung surfactant by group B streptococci

In newborn infants, group B streptococci (GBS) often cause pneumonia, with polymorphonuclear leukocytes (PMN) migrating into the lungs. Because surfac tant therapy may be needed in such patients, we evaluated the interaction b etween GBS or GBS-stimulated PMN and a surfactant preparation (Curosurf) in vitro. The superoxide production of GBS strains or GBS-activated PMN was m easured, using the nitroblue tetrazolium (NBT) test and the subsequent lipi d peroxidation (LPO) as the content of malondialdehyde (MDA) and 4-hydroxya lkenals (4-HNE). The growth of GBS in surfactant was determined and related to the LPO, Finally, the effect of LPO on surfactant activity, caused by G BS-stimulated PMN, was assessed by measuring dynamic surface tension in a p ulsating bubble surfactometer. Curosurf diminished the NET reduction by bot h live GBS and GBS-stimulated PMN. Surfactant was peroxidized by reactive o xygen species (ROS) from both GBS and GBS-stimulated PMN in a time-dependen t manner. Vitamin E significantly reduced the peroxidation level of surfact ant in both cases. Surfactant peroxidation was associated with a reduction in the number of live bacteria. The biophysical activity of Curosurf was im paired by GBS-stimulated PMN, as reflected by increased minimum surface ten sion during cyclic compression. These findings indicate that Curosurf under goes LPO by ROS produced by GBS and/or PMN. We speculate that exogenous sur factant preparations should be supplemented with vitamin E or another antio xidant, when given to infants with GBS pneumonia.