Altered surfactant protein B levels in transgenic mice do not affect clearance of bacteria from the lungs

To determine the role of surfactant protein B (SP-B) in bacterial clearance from the airways, three groups of mice expressing different levels of SP-B were studied: wild-type mice, hemizygous SP-B mice, and SP-B overexpressin g transgenic mice. SP-B levels in overexpressing mice were increased 5-fold relative to hemizygous mice and 2- to 3-fold over wild-type littermates. M ice from each group were infected intratracheally with the common airway pa thogens, group B streptococci or Pseudomonas aeruginosa. There was no signi ficant difference in the number of recoverable viable bacteria at 6 h (grou p B streptococci and P. aeruginosa) and at 24 h (P. aeruginosa) among the t hree groups. Similarly, systemic dissemination of bacteria was not differen t among the three groups for both pathogens and at both time points. We con clude that SP-B levels in vivo do not influence clearance of bacteria from the lungs.