Haemagglutination and surface structures in strains of Clostridium spiroforme

Five strains of Clostridium spiroforme were examined for their surface properties. All strains were able to agglutinate human erythrocytes. Electron microscopy showed a ruthenium red-positive capsule mediating the attachment of bacteria to erythrocytes. Two strains, showing the lowest degree of haemagglutination, exhibited an additional external layer of filamentous structures, possibly interfering with the agglutinating activity. In spite of their agglutinating ability, the C. spiroforme strains did not show surface hydrophobicity, thus suggesting the possible existence of a new type of clostridial adhesin.