BRANHAMELLA-CATARRHALIS - EPIDEMIOLOGY, SURFACE ANTIGENIC STRUCTURE, AND IMMUNE-RESPONSE

Over the past decade, Branhamella catarrhalis has emerged as an import ant human pathogen. The bacterium is a common cause of otitis media in children and of lower respiratory tract infections in adults with chr onic obstructive pulmonary disease. B. catarrhalis is exclusively a hu man pathogen. It colonizes the respiratory tract of a small proportion of adults and a larger proportion of children. Studies involving rest riction enzyme analysis of genomic DNA show that colonization is a dyn amic process, with the human host eliminating and acquiring new strain s frequently. The surface of B. catarrhalis contains outer membrane pr oteins, lipooligosaccharide, and pili. The genes which encode several outer membrane proteins have been cloned, and some of these proteins a re being studied as potential vaccine antigens. Analysis of the immune response has been limited by the lack of an adequate animal model of B. catarrhalis infection. New information regarding outer membrane str ucture should guide studies of the human immune response to B. catarrh alis. Immunoassays which specifically detect antibodies to determinant s exposed on the bacterial surface will elucidate the most relevant im mune response. The recognition of B. catarrhalis as an important human pathogen has stimulated research on the epidemiology and surface stru ctures of the bacterium. Future studies to under-stand the mechanisms of infection and to elucidate the human immune response to infection h old promise of developing new methods to treat and prevent infections caused by B. catarrhalis.