Transmission electron microscopy studies of Moraxella (Branhamella) catarrhalis

A trypsin-sensitive 200-kDa protein has been reported to be exclusive assoc iated with haemagglutinating isolates of Moraxella (Branhamella) catarrhali s. Transmission electron microscopy studies revealed that haemagglutination by M. catarrhalis to both human and rabbit erythrocytes was mediated by a trypsin-sensitive outer fibrillar coat. This fibrillar layer was absent on non-haemagglutinating isolates examined. Immune-electron microscopy, using a polyclonal antiserum containing antibodies to the 200-kDa protein as a pr obe, showed that the 200-kDa protein is present on the outer fibrillar laye r of the bacterium. These findings suggest that the haemagglutinin of M. ca tarrhalis is a 200-kDa protein present on the outer fibrillar coat. (C) 199 9 Federation of European Microbiological Societies. published by Elsevier S cience B.V. All rights reserved.