[Oropharyngeal colonization by Gram-negative bacteria in elderly hospitalized patients: incidence and risk factors].

Purpose: In a prospective study, we determined the predisposing conditions and the course of aerobic Gram-negative bacilli oropharyngeal colonization during the hospital stay in patients older than 70 years.

Methods: We studied 116 patients admitted in our internal medicine unit. Medical characteristics were documented for each patient. Oropharyngeal swabs were collected on the first, third, and seventh days after admission, and then once a week until discharge. Positive culture was defined as the presence of at least one colony of Gram-negative bacilli.

Results: We collected 306 samples from the 116 patients. The mean hospital stay was 10.6 days. Fifty patients (43%) had at least one positive oropharyngeal culture. Thirty-three patients (30%) were colonized on admission, but this prevalence decreased during hospital stay: 20% on the third day and 14% on the seventh day. In an univariate analysis, prior administration of antibiotics (P < 0.01) and use of nonsteroid anti-inflammatory drugs (P < 0.05) were associated with colonization.

Conclusion: Aerobic Gram-negative bacilli oropharyngeal colonization was transient during the hospital stay in the elderly. The use of nonsteroidal anti-inflammatory drugs and the previous treatment with antibiotics are possible risk factors for colonization.