Use of Tracheal Aspirate Culture in Newly Intubated Patients with Community-Onset Pneumonia

Rationale: Successful treatment of life-threatening community-acquired pneumonia requires appropriate empiric antibiotic coverage. But using conventional diagnostic techniques, a microbiological diagnosis is often not achieved. The diagnostic usefulness of tracheal aspirate at the time of intubation in patients with severe pneumonia has not been well studied.

Objectives: The purpose of this study was to evaluate the use of tracheal aspirate culture in identifying pneumonia pathogens.

Methods: We identified all patients older than 18 years of age with International Classification of Disease, Ninth Revision codes and radiographic evidence of pneumonia seen in the emergency departments at 2 university-affiliated Utah hospitals from December 2009 to November 2010 and from December 2011 to November 2012. Patients intubated within 24 hours of arrival were then identified electronically. Postintubation orders instructed respiratory therapists to obtain tracheal aspirate for culture. All culture results were reviewed individually and defined as positive if a pneumonia pathogen was identified. Results of other microbiology studies were obtained from the electronic medical record.

Measurements and main results: Of 2,011 patients with pneumonia, 94 were intubated and 84 had a tracheal aspirate obtained. Of these 84 patients, 47 (56%) had a pulmonary pathogen identified by tracheal aspirate culture, 80 also had blood cultures, and 71 underwent Pneumococcal and Legionella urinary antigen testing. A microbiological diagnosis was made in 55 patients (65.5%) by any diagnostic method. In 39% of patients (32 of 82), the tracheal aspirate culture was the only positive test, resulting in a unique microbiological diagnosis in patients who would have otherwise been classified as "culture negative."

Conclusions: Tracheal aspirate cultures obtained as part of routine care identified a plausible pneumonia pathogen in more than one-half of emergency department adult patients with severe pneumonia requiring intubation. Tracheal aspirate culture offers important additive diagnostic value to other routine tests.