Pathogenesis of Colonization/Infection of Lower Airways (Endogenous vs Exogenous): Conventional Approaches to Infection Control

Abstract

An understanding of the pathogenesis of lower airway colonization is essential in formulating plans to prevent nosocomial respiratory infection. Airway colonization is a frequent harbinger of nosocomial pneumonia, and prevention of its occurrence could proceed in one of two ways: either the impairments in host defence that promote colonization could be bolstered, or selective decontamination techniques could be applied. Based on data derived from the study of bacterial adherence to respiratory epithelial cells, it may be necessary to re-examine some of the principles of nosocomial pneumonia prophylaxis with topical antimicrobials. While decontamination of the oropharynx and intestinal tract can eliminate most enteric gram-negative bacteria from entering the lower airway, this approach may not prevent tracheobronchial colonization by Pseudomonas species, particularly if these organisms are present in the general intensive care unit environment. To eliminate colonization of the airway by these organisms in critically ill patients it may be necessary to manipulate host defences or to extend decontamination techniques directly to the tracheobronchial tree.