Quantitative Bacterial Cultures of Bronchoalveolar Lavage Fluids and Protected Brush Catheter Specimens from Normal Subjects

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Abstract
Bronchoalveolar lavage (BAL) is quite useful in the diagnosis of nonbacterial lung infections, especially in immunocompromised patients, and recent studies have suggested that BAL may be useful in the diagnosis of bacterial pneumonia as well. Because previous studies indicated that bronchoscopic aspirates are usually contaminated by oropharyngeal flora, we anticipated that BAL fluid would also likely be contaminated. Therefore, the purpose of this study was to perform quantitative bacterial cultures on BAL fluids obtained from eight normal subjects. Prior to each procedure, saline was aspirated through the bronchoscope and submitted for culture. A protected brush catheter (PBC) specimen was obtained from each subject''s right middle lobe, and then a BAL specimen was obtained from the same location. All specimens were quantitatively cultured for aerobic and anaerobic organisms. In addition, lidocaine concentrations were measured in the BaL fluids and the PBC specimens. Six of the eight bronchoscope cultures were sterile. Seven of the eight PBC specimens were sterile and one yielded (< 103 cfu/ml of normal oropharyngeal flora. One BAL fluid specimen was sterile and seven yielded from one to four bacterial strains each; however, quantitation revealed < 104 cfu/ml in all specimens. Lidocaine concentrations (mean .+-. 1 SD) were as follows: PBC specimen, 0.81 .mu.g/ml (.+-. 0.62); BAL fluid specimen, 62.6 .mu.g/ml (.+-. 43). We conclude that BAL fluid obtained from normal subjects is frequently contaminated by oropharyngeal bacterial flora. However, quantitation of bacteria recovered from BAL fluid may allow separation of contaminant from pathogenic organisms. Also, lidocaine concentrations found in these specimens should have no important effects on recovery of bacteria by either of these techniques.