Ethanol ingestion reduces antipneumococcal activity of rat pulmonary surfactant

Because chronic ethanol ingestion decreases pulmonary clearance of Streptococcus pneumoniae in rats, and extracellular antipneumococcal factors in rat surfactant are important in the early clearance of pneumococci from the rat alveolus, the effects of ethanol ingestion on surfactant bactericidal activity were investigated. Normal surfactant from chow-fed rats showed potent antipneumococcal activity, even against bacteria growing in nutrient- rich media under favorable conditions. In contrast, surfactant from ethanol- fed rats and from calorie-restricted control-fed rats had significantly reduced antipneumococcal activity compared with surfactant from chow-fed rats. The reductions in surfactant bactericidal activity produced by ethanol ingestion or caloric restriction did not appear to be mediated through changes in either the total amount or the distribution of fatty acids, the antipneumococcal factors in normal surfactant. Rather, ethanol ingestion, and to a lesser extent caloric restriction, produced a surfactant inhibitor of free fatty acids that was partially characterized as a hydrophobic protein.