Diagnosis of nosocomial pneumonia in intubated, intensive care unit patients.

The clinical distinction between bacterial colonization of the tracheobronchial tree and nosocomial pneumonia is difficult, especially in intubated patients. We studied 51 intubated, intensive care unit patients prospectively by serial examinations of tracheal aspirates for elastin fibers, graded Gram's stains, and quantitative bacterial cultures in conjunction with clinical and radiologic observations in an attempt to develop criteria for the early detection of pulmonary infection. Patients with infection had new or progressive pulmonary infiltrates plus 1 of the following: positive blood culture results, radiographic evidence of cavitation, or histologic evidence of pneumonia, or 2 or more of the following: new fever, new leukocytosis, or grossly purulent tracheal aspirates. Twenty-one patients developed infection, 22 remained colonized, and 8 had an uncertain status. Infiltrates developed in 34 patients (21 infected, 8 colonized, 5 uncertain status). Gram-negative bacilli were most commonly isolated and were more frequent in infected patients (81 versus 47%, p less than 0.05); Pseudomonas aeruginosa and Serratia marcescens were most often associated with infection. No differences were observed between infected and colonized patients in demographic features, smoking history, underlying disease, previous antibiotic therapy, days in hospital before intubation, preexisting pneumonia upon intubation, or highest temperature or leukocyte count during course. By univariate analysis, infected patients had a longer duration of intubation (p less than 0.05), higher Gram's stain grading for neutrophils (p less than 0.05) or bacteria (p less than 0.005), higher bacterial colony counts (p less than 0.05), and more frequent detection of elastin fibers in tracheal aspirates (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)