Is the stomach an important source of tracheal contamination and subsequent pneumonia?

Objective: To determine the role of gastric colonization in the development of tracheal contamination and subsequent pulmonary infection in critically ill patients. Design: Observational cohort study. Setting: Eight tertiary care medical-surgical intensive care units. Participants: ICU patients expected to remain ventilated > 48 hours. We excluded patients with gastrointestinal bleeding, acidaemia, and renal failure. We studied 95 patients receiving continuous enteral nutrition; 38% were female, mean age (SD) was 55.1 (±18.9) years, and mean APACHE II Score was 21.6 (±7.0). Interventions: We prospectively documented microbial growth patterns in the stomach, trachea and enteral feeding reservoir (EFR). At baseline and every Monday, Wednesday and Friday, we sampled the EFR and stomach. Specimens were sent to the microbiology laboratory for culture. Patients were followed for the development of ICU-acquired pneumonia. Measurements and results: Fifty-four patients (56.8%) had a positive tracheal culture during their ICU stay; 10 (10.5%) developed pneumonia. Of the 11 organisms implicated in the aetiology of the 10 cases of pneumonia, six first appeared in the stomach, one appeared in the stomach and EFR at the same time, one appeared in the EFR first, and three organisms appeared only in the lungs. Patients who were colonized in the stomach were significantly more likely to develop pneumonia than those who were not colonized in the stomach (odds ratio 4.2, 95%CI 1.2-15.5). Of 62 organisms isolated from multiple sites in 39 patients, organisms first appeared in the stomach and then the trachea in 32 cases (51.6%), first the EFR and then the trachea in two cases (3.2%), the trachea and stomach simultaneously in five cases (8.1%) and from the trachea first in 23 cases (37.1%). Conclusions: Microorganisms in the stomach may predispose critically ill patients to contamination of tracheal secretions and ICU-acquired pneumonia.