Lipid peroxidation of lung surfactant by bacteria

The epithelium of the lung is lined with extracellular pulmonary surfactant . This is the surface that invading bacteria first come into contact with w hen they enter the alveoli. As bacteria become established and interact wit h this layer, various characteristics of surfactant may become altered. We studied free radical production by three bacterial species, group B strepto cocci, Escherichia coli, and Pseudomonas aeruginosa, as well as the effect of two concentrations of lung surfactant (Curosurf at 0.04 and 0.4 mg/ml) o n this production estimated by the nitro blue tetrazolium reduction test. W e also measured the lipid peroxidation of surfactant at various incubation times (0-20 h), using a LPO-586 test kit. In addition, the effect of vitami n E as an antioxidant in a concentration of 0.5 M was determined by the lip id peroxidation test. We found that the nitro blue tetrazolium reduction by the three bacterial species and lipid peroxidation of lung surfactant incr eased with time. Vitamin E reduced the lipid peroxidation of this surfactan t. By measuring bacterial growth at various incubation times we showed that lung surfactant was bactericidal to group B streptococcal and E. coli stra ins and that P. aeruginosa strains were resistant to surfactant. We conclud e that bacteria, probably by their production of reactive oxygen species, c ause lipid peroxidation of lung surfactant.