Differing pathways of lower airway colonization and infection according to mode of ventilation (endotracheal vs tracheotomy).

Objectives: To determine whether the pathogenesis of lower airway colonization and infection was endogenous (via the oropharynx) or exogenous (via the endotracheal tube or tracheotomy) during the 2 modes of ventilation in the same subset of children requiring long-term ventilation.

Design: Prospective, observational cohort study.

Setting: A pediatric intensive care unit and a respiratory ward.

Patients: Consecutive admissions between September 1, 1993, and August 30, 1998.

Measurements And Main Results: Cultures were obtained simultaneously from the oropharynx and tracheobronchial tree on admission to the pediatric intensive care unit, at placement of the tracheotomy, and afterward twice weekly. Forty-five patients were studied. Lower airways were always sterile in 6 children, 39 children (87%) developed a total of 82 episodes of colonization, and 17 (38%) progressed to 25 episodes of infection. The number of infected children was halved once they had a tracheotomy (7 children [16%]). Of the 107 episodes of colonization and infection, 41 and 66 occurred during endotracheal ventilation and via a tracheotomy, respectively. Primary endogenous episodes of colonization and infection due to bacteria present in the admission flora in the pediatric intensive care unit were significantly more common with endotracheal ventilation than during ventilation via a tracheotomy (31/41 [76%] vs 36/66 [55%]; P =.03). Secondary endogenous and exogenous episodes of colonization and infection due to bacteria associated with the respiratory ward were significantly more frequent when ventilation was continued through a tracheotomy than during endotracheal ventilation (30/66 [45%] vs 10/41 [24%]; P =.02).

Conclusions: Surveillance samples allow the distinction between primary endogenous ("imported" bacteria) from secondary endogenous and exogenous ("nosocomial" microorganisms) colonization and infection. This classification permits the development of preventive strategies to control both endogenous and exogenous pathways.