Immunoglobulin G (IgG) serological response to Branhamella catarrhalis in patients with acute bronchopulmonary infections.

Over 12 months serum was collected from 45 inpatients, with acute bronchopulmonary infection, in whose sputum Branhamella catarrhalis predominated, or was the sole pathogen. Serum was examined for IgG against B catarrhalis using an immunofluorescence antibody test. Acute and convalescent sera were compared with sera of age and sex matched controls. The convalescent sera had significantly higher titres than the acute sera which in turn had higher titres than the controls. The findings confirm the role of B catarrhalis as a respiratory pathogen and suggest that patients with chronic pulmonary disease are more prone to infection with this organism than the general population.