Risks and routes for ventilator-associated pneumonia with Pseudomonas aeruginosa

In a prospective study, we screened specimens from 190 mechanically ventilated patients hospitalized in a surgical intensive care unit, and from the environment to assess risks and routes of colonization/infection. Specimens from various sites were collected on admission and once a week throughout each patient's stay. All P. aeruginosa isolates were typed by determination of DNA patterns. Data were collected from patients to identify risk factors. In vitro production of exoenzymes of different strains were compared. Forty-four patients were colonized with P. aeruginosa on the bronchopulmonary tract and 13 suffered from pneumonia. The 7-d and 14-d Kaplan-Meier rates of colonization were 2.21 and 7.03%. Twenty-one patterns of bronchopulmonary tract isolates were isolated from single patients and 10 from several patients. The lower airway was often the first site of colonization. The contribution of environment to patient colonization appeared to be small. The length of hospitalization, the previous use of third-generation cephalosporins less effective against P. aeruginosa, and chronic obstructive pulmonary disease were the most significant predictors of colonization/infection. The in vitro exoprotein production was not correlated with the presence of pneumonia. Our study may be useful in identifying which patients in the mechanically ventilated population are at greater risk of P. aeruginosa pneumonia.