[The role of gastro-intestinal tract microorganisms in the development of ventilator-associated pneumonia: an experimental study].

Objective: To study the role of microorganisms in the gastro-intestinal (GI) tract in the development of ventilator-associated pneumonia (VAP).

Methods: Forty-four healthy New Zealand white rabbits were randomly divided into a control group (n = 2), a mechanical ventilation (MV) group (n = 5), a mechanical ventilation with bacterial gastric inoculation (B) group (n = 11), a mechanical ventilation with bacterial gastric inoculation plus mosapride citrate (P) group (n = 13), and a mechanical ventilation with bacterial gastric inoculation plus loperamide (I) group (n = 13). 5% NaHCO3 was used to remain the pH value of gastric juices higher than 3.0. The flora in oropharynx, bronchi, and gastric juices were monitored during mechanical ventilation (MV). The pulmonary score and bacterial culture of the lung were performed at the end of mechanical ventilation.

Results: The incidence of lung infection caused by gastric bacterial inoculation was 10.8% (4/37). Taken together, mosapride citrate and loperamide didn't alter the incidence of VAP (chi2 = 0.83, P > 0.05), however, the occurrence of lung infection caused by inoculated bacteria in P group was lower than that in I group [(0.0%, 0/13) vs (23.1%, 3/13), chi2 = 4.55, P < 0.05]; the time of the emergence of the gastric inoculated bacteria in oropharynx in P group was later than that in I group; and the pulmonary score of B group was higher than that of MV group.

Conclusions: Bacteria in the GI tract were not the main source of early-onset VAP, however, they may contribute to the development of late-onset VAP. Gastrointestinal dynamic promoting drugs, which enhance gastrointestinal motility, are useful to reduce the incidence of VAP caused by bacteria colonized in the digestive tract.