Antibody coating and quantitative cultures of bacteria in sputum and bronchial brush specimens from patients with stable chronic bronchitis.

Antibody coating of bacterial isolates has been proposed as a method of identifying bacteria responsible for chronic lower respiratory infections. This study was designed to determine the specificity of antibody coating by examining bronchial secretions obtained from a group of patients with chronic bronchitis who had no clinical evidence of acute infection. Routine and quantitative bacterial cultures were performed at the same time. The bronchial brush specimens contained potentially pathogenic bacteria in all 18 patients examined, and 17 of these 18 specimens had antibody coating of bacteria. Quantitative cultures yielded greater than 10(4) colony forming units in only one patient and he subsequently developed a lower respiratory tract infection. We conclude that in patients with chronic bronchitis, the determination of antibody coating of bacterial isolates does not significantly increase the specificity of routine culture. Quantitative cultures of specimens obtained via the protected brush catheter are useful in identifying potential pathogens.