Bronchoalveolar lavage for diagnosing acute bacterial pneumonia.

The utility of gram stain and semiquantitative culture of the fluid retrieved by bronchoalveolar lavage (BAL) in identifying the causative agent in acute bacterial pneumonia was initially assessed in 92 patients. Fifteen of these patients presented with clinically active bacterial pneumonia; the remaining patients underwent bronchoscopy to evaluate other processes in the lung. Thirteen of the 15 patients with clinically active bacterial pneumonia had a BAL culture greater than or equal to 10(5) colony-forming units per milliliter of BAL fluid, whereas none of the other groups had a positive culture (chi 2 = 70.7, P less than .001). Gram stain of cytocentrifuged BAL fluid was positive (one or more organisms seen per 1,000 X field) only in those patients with an active bacterial pneumonia. Applying this technique, we studied 59 immunocompromised patients presenting with pulmonary infiltrates. Eight (21%) of the 39 patients presenting with microbial-related infiltrates proved to have acute bacterial pneumonia by BAL culture; the pneumonia resolved with appropriate antimicrobial therapy.