The effect of intraalveolar fluid on lung bacterial clearance

Abstract

Appropriate animal models of lung bacterial clearance are difficult to establish in part because our current understanding of the pathogenesis of human pneumonia is imprecise. If all available models produced similar data their relevance to human infection would be strengthened. To assess consistency between two such models, we studied the effects of pulmonary edema and intratracheally injected protein on the pulmonary clearance of either aerosolized or intratracheally injectedStaphylococcus aureus orStreptococcus pneumoniae. Intraalveolar fluid, whether produced by increasing pulmonary capillary permeability or by intratracheal inoculation of bacteria, impaired lung bacterial clearance. This impairment varied with the organism employed. Proteinaceous intraalveolar fluid does not impair clearance by supporting bacterial multiplication and may enhance clearance of some organisms. Our results suggest that animal models of human lung infection are not easily constructed, remain problematic, and, at best, are only valid for the specific conditions of the model.