[Respiratory tract infections caused by Branhamella catarrhalis in outpatients with pneumoconiosis]. 
To investigate the occurrence of Branhamella catarrhalis respiratory tract infections in 109 outpatients with pneumoconiosis, clinical and bacteriological studies were performed during a 4-year period from April 1984 to March 1988.  B. catarrhalis was isolated in 26 patients; only three of these received continuous corticosteroid treatment.  The incidence of B. catarrhalis respiratory tract infections increased gradually during the years 1984-1986, but decreased for the first time in 1987 compared with the previous year.  There was a seasonal variation in isolations with a peak incidence during the winter, a pattern in contrast to Haemophilus influenzae.  Almost all isolates produced beta-lactamase.  B. catarrhalis found in mixed culture was usually in association with H. influenzae or Streptococcus pneumoniae.  The isolation rates for B. catarrhalis in sputum of patients with pneumoconiosis followed those of H. influenzae and S. pneumoniae, and almost all strains were positive for beta-lactamase, so B. catarrhalis should be admitted that it is a primary pathogen.