The lower airways of asymptomatic chronic obstructive pulmonary disease (COPD) patients can be colonized by bacteria, mainly Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis. However, the role of lower airway bacteria in stable and exacerbated COPD has not been well defined. To determine the importance of lower airway bacterial infection in COPD we studied 40 outpatients with stable COPD (Group A: age 61.1 +/- 9.9 yr; [mean +/- SD]; FEV(1)/FVC 51.7 +/- 12.5) and 29 outpatients with exacerbated COPD (Group B: age 63.4, SD 9.0 yr; FEV(1)/FVC 52.0, SD 9.6), using the protected specimen brush (PSB) for microbiology sampling. Group A consisted of outpatients with stable COPD having normal or near-normal chest X-rays, with clinical indications for performing fiberbronchoscopy (pulmonary nodule, remote hemoptysis); Group B consisted of patients with exacerbated COPD who voluntarily accepted lower airway microbiology sampling. To avoid contamination by upper airway flora the PSB was used for bacterial sampling in all the cases and concentrations greater than or equal to 1,000 colony-forming units/milliliter (CFU/ml) were considered positive. Results were as follows: Group A: Lung function data in outpatients with stable COPD were lower than the reference values for this population (FVC 2.97 +/- 1.02 L, FVC% 71.4 +/- 22.4, FEV(1) 1.59 +/- 0.79 L, FEV(1)% 51.2 +/- 23.0). Positive PSB cultures were obtained in 10 of 40 cases (25%), mainly of H. influenzae and S. pneumoniae. Two of 40 cases had positive cultures at concentrations greater than or equal to 10,000 CFU/ml (5.0%). Group B: Lung function data in outpatients with exacerbated COPD were lower than the reference values (FVC 2.47 +/- 0.78 L, FVC% 61.7 +/- 16.2, FEV(1) 1.29 +/- 0.48 L, FEV(1)% 43.8 +/- 14.0). Positive PSB cultures were found in 15 of 29 cases (51.7%), in 7 of 29 cases at concentrations greater than or equal to 10,000 CFU/ml (24.1%).The most commonly found bacteria were H. influenzae and S. pneumoniae. Comparison of the prevalence of positive bacterial cultures in the two groups showed a higher prevalence in exacerbated COPD (p = 0.043), a difference that was more apparent when only concentrations greater than or equal to 10,000 CFU/ml were considered (stable COPD 5.0%; exacerbated COPD 24.1%; p = 0.03). We conclude that the prevalence of lower airway bacterial colonization in outpatients with stable COPD is high (25.0%) and is mainly due to H. influenzae and S. pneumoniae. Exacerbated COPD is related to bacterial infection as demonstrated by the significantly higher prevalence (51.7%) of positive results as well as higher bacterial concentrations determined in cultures grown after PSB sampling of the lower airway.
