Recurrent respiratory tract infection caused by Moraxella catarrhalis in patients with pneumoconiosis

: Moraxella catarrhalis is recognised as a major pathogen in chronic respiratory diseases. Patients with pneumoconiosis have repeated respiratory infections, and the control is very important for good prognosis. From 1988 to 1993, fifty strains of Moraxella catarrhalis were obtained from 9 patients with pneumoconiosis attended at Nagasaki Rosai Hospital. Restriction enzyme analysis of chromosomal DNA by Hind III. Hae III, Cla I was performed on 50 strains of M. catarrhalis. Twelve strains (56%) out of 23 isolates with interval of less than 5 months had identical bacterial restriction endonuclease digestion patterns with three different enzymes, and all isolates with interval more than 6 months had different patterns. Tweny out of 13 episodes by the same strains occurred during 3 months. The acquisition and clearance of M. catarrhalis from the respiratory tract is a dynamic process.