Influence of modified natural or synthetic surfactant preparations on growth of bacteria causing infections in the neonatal period

Connatal bacterial pneumonia is common in neonates. Animal studies and init ial clinical reports indicate that surfactant dysfunction is involved in th e pathophysiology of severe neonatal pneumonia. Since respiratory distress syndrome and connatal pneumonia may be difficult to differentiate in the fi rst hours of life, neonates with respiratory failure due to bacterial infec tions might receive surfactant. Under such conditions surfactant components might be catabolized by bacteria and promote bacterial growth. We therefor e investigated the influence of three modified natural (Curosurf, Alveofact , and Survanta) and two synthetic (Exosurf and Pumactant) surfactant prepar ations on the growth of bacteria frequently cultured from blood or tracheal aspirate fluid in the first days of life. Group B streptococci (GBS), Stap hyloccocus aureus, and Escherichia coli were incubated in a nutrient-free m edium (normal saline) for 5 h at 37 degrees C, together,vith different surf actants at concentrations of 0, 1, 10, and 20 mg/ml, With the exception off . coli, incubation in saline alone led to a variable decrease in CFU, In th e presence of Alveofact, Exosurf, and Pumactant the decline in bacterial nu mbers was less marked than in saline alone. Curosurf was bactericidal in a dose-dependent fashion for GBS and had a strong negative impact on the grow th of a GBS subtype that lacked the polysaccharide capsule. In contrast, Su rvanta (10 and 20 mg/ml) significantly promoted the growth of E. coli, indi cating that surfactant components may actually serve as nutrients. We concl ude that bacterial growth in different surfactant preparations is influence d by microbial species and the composition and dose of the surfactant, Furt her studies are necessary to elucidate the mechanisms behind our findings a nd to evaluate the effects of surfactant on bacterial growth in vivo.