Diagnosing Bacterial Respiratory Infection by Bronchoalveolar Lavage

Abstract

We prospectively evaluated 75 patients by fiber-optic bronchoscopy and bronchoalveolar lavage (BAL) for the presence of bacteriallower-respiratory-tract infection. BAL specimens were cultured quantitatively for aerobic bacteria, and a cell differential was obtained of the BAL cell population. In 18 “control” patients without evidence of respiratory infection, the presence of >1% squamous epithelial cells (SECs) in the BAL sample accurately predicted the presence of heavy contamination of the sample by oropharyngeal flora. In the remaining “study” patients with potential infection, polymorphonuclear leukocytes were readily identified, and potentiallower-respiratory-tract pathogens were recovered in concentrations >10⁵ colony-forming units (cfu) per milliliter in 16 of 18 patients with bacterial infection (none had >1% SECs in their BAL sample). No patients without evidence of bacterial infection and with ⩽1% SECs had >10⁵ cfu/ml in BAL cultures. These studies establish the ability of BAL techniques to diagnose bacterial respiratory infection.