Prediction of tracheobronchial colonization in current cigarette smokers with chronic obstructive bronchitis.

To help in clarifying the conflicting data on the role of tracheobronchial microflora in chronic bronchitis, the tracheobronchial microflora of a homogeneous group of clinically stable patients with chronic obstructive bronchitis was characterized by transtracheal aspiration. Their mean percentage ratio of forced expiratory volume in 1 sec to the forced vital capacity was 45%. The results were that (1) a bacterial tracheobronchial microflora was present in only 50% of the patients, (2) viridans streptococci were the bacteria most frequently isolated, and (3) the presence or absence of a tracheobronchial microflora was significantly associated with the amount of present cigarette smoking. The fact that patients who smoke less than one pack per day were most likely to have a sterile tracheobronchial tree (P=0.015) implied that there was a critical amount of cigarette smoke that impaired the clearance and/or detoxification of bacteria from the tracheobronchial tree and that it must have been persistently present.