The Use of Quantitative Sterile Brush Culture and Gram Stain Analysis in the Diagnosis of Lower Respiratory Tract Infection

We prospectively evaluated 55 patients (58 studies) who presented for diagnostic fiberoptic bronchoscopy for the presence of lower respiratory tract infection. A sheathed, nonplugged, sterile brush passed transbronchoscopically under fluoroscopic control was used to retrieve bronchial secretions. These were evaluated using Gram stains, Wright-Giemsa stains, and quantitative bacterial cultures. In 18 studies of patients with known or suspected infection, polymorphonuclear leukocytes and bacteria were easily identifiable on Gram stain, and potential lower respiratory pathogens were recovered in concentrations ≥ 106 colony-forming units (cfu)/ml. In 15 control studies of patients with noninfectious lung disease and in 17 studies of patients with suspected lung infection (nine with prior antibiotic therapy), organisms were not seen on Gram stain and in 28/32 studies bacteria were present in concentrations of ≤ 104 cfu/ml. The remaining eight studies were in patients proved to have active granulomatous disease. These studies establish the ability of a fiberoptic bronchoscopic technique to diagnose bacterial infection in a group of patients presenting difficult diagnostic problems.