Prospective study of nosocomial colonization and infection due to Pseudomonas aeruginosa in mechanically ventilated patients

Objective:To investigate the respective contribution of endogenous and exog enous transmission of Pseudomonas aeruginosa in the colonization of lungs i n the mechanically ventilated patient, to estimate the role of P. aeruginos a colonization in the occurrence of severe infections, and to extrapolate a ppropriate control measures for the prevention of P. aeruginosa ventilator- associated pneumonia. Design: Prospective study of the presence of P. aeruginosa tin stomach flui d, throat specimens, stool, and sputum) on admission, twice a week througho ut the patient's stay, and in their environment. O-sero-typing, pulsed-fiel d gel electro; phoresis, and arbitrarily-primed polymerase chain reaction w ere used to characterize the strains. Setting: The two intensive care units (ICUs 1 and 2) of a university hospital. Patients: During a 6-month period, 59 patients were included (21 in ICU 1 a nd 38 in ICU 2). Results: P. aeruginosa was isolated in 26 patients, including ten pneumonia cases and seven colonizations on admission. The incidence of acquired colo nization was statistically different between the two ICUs: 5.5 and 20.5 per 1000 days of mechanical ventilation, in ICUs 1 and 2, respectively. Endoge nous acquisition was the main origin of P. aeruginosa colonization (21 of 2 6 patients) and the upper respiratory tract was the main bacterial reservoi r in bronchopulmonary colonization and infection. However, during the 6-mon th period of the study, a multidrug-resistant strain of P. aeruginosa 0:11, isolated in the sink of the room of 12 patients, was found responsible for two colonizations (1 digestive, 1 throat/lungs) and one pneumonia. As a wh ole, from 26 cases of colonization/infection with P. aeruginosa, 5 were rel ated to an exogenous contamination (environmental reservoir in 4 patients a nd cross-contamination in one patient). Conclusions: These results emphasize the need for applying various infectio n control measures to prevent colonization of patients with II aeruginosa, including strategies to limit the potential of sinks from acting as a sourc e or reservoir for this bacterium.