Studies of the outer membrane proteins of Branhamella catarrhalis

purpose: Branhamella catarrhalis has emerged as an important human pathogen in the past several years. Therefore, studies of the outer membrane have been undertaken in order to identify virulence factors and begin to understand the immune response to infection. materials and methods: The outer membrane of B. catarrhalis has been purified by sucrose density centrifugation. The outer membrane proteins (OMPs) of 50 strains from diverse sources were isolated by simpler methods and studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Experiments were designed to identify OMPs that express determinants on the surface of the intact bacterium. results: Eight major OMPs have been identified (OMPs A through H). The OMP patterns from diverse strains were strikingly similar. OMP E (approximately 56,000 daltons) and OMP G (approximately 28,000 daltons) have determinants that are surface-exposed and these determinants are shared among a majority of strains of B. catarrhalis. conclusion: These observations have important implications with regard to the immune response to infection and future vaccine development.