[Pathogenesis and environmental factors in ventilator-associated pneumonia]

Respiratory infections in intubated patients can derive from endogenous or exogenous sources. The major route for acquiring endemic ventilator-associated pneumonia (VAP) is oropharyngeal colonization by endogenous flora and leakage of contaminated secretions into the lower respiratory tract. However, a not inconsiderable percentage of VAP results from exogenous nosocomial colonization, especially pneumonias caused by resistant bacteria such as methicillin-resistant Staphylococcus aureus and multiresistant Acinetobacter baumannii or Pseudomonas aeruginosa, as well as by Legionella spp or filamentous fungi, such as Aspergillus. This article reviews the pathogenesis of VAP and the role of the intensive care environment as a source of pathogenic microorganisms.