HEMAGGLUTINATION PROPERTIES OF MORAXELLA (BRANHAMELLA) CATARRHALIS

The ability of 30 isolates of Moraxella (Branhamella) catarrhalis to h aemagglutinate erythrocytes of five species was examined. Two haemaggl utination phenotypes of M. catarrhalis were observed: phenotype I isol ates (n = 10) agglutinated human erythrocytes, while phenotype II isol ates (n = 7) agglutinated both human and rabbit erythrocytes. No haema gglutination was observed with chick, sheep or horse erythrocytes. Hae magglutination by both phenotype I and II isolates was abolished follo wing treatment of these isolates with pronase and trypsin, while heat treatment at 70 degrees C markedly reduced the level of haemagglutinat ion by both sets of isolates. Haemagglutination by phenotype II isolat es was inhibited by galactose, whereas haemagglutination by phenotype I isolates was not inhibited by this carbohydrate. Transmission electr on microscopy (TEM) studies showed that very close cell-surface intera ctions occurred when both phenotypes of M. catarrhalis adhered to the human erythrocyte. Fimbrial attachment was not apparent. Haemagglutina ting isolates of both phenotypes had a trypsin-sensitive outer fibrill ar coat when examined by TEM.