A HEMAGGLUTINATING ADHESIN OF GROUP-B STREPTOCOCCI ISOLATED FROM CASES OF BOVINE MASTITIS MEDIATES ADHERENCE TO HELA-CELLS

Rabbit erythrocytes were agglutinated by 43.4% of group B streptococci isolated from bovines but by none isolated from humans. Haemagglutina tion was enhanced by cultivation of the bacteria under microaerophilic conditions. Most of the haemagglutinating strains had protein type an tigen X, either alone, or in combination with polysaccharide antigens. Heat and proteolytic treatment of the bacteria destroyed the haemaggl utination activity. The haemaggtutinin could be solubilized from the b acterial surface by mutanolysin treatment and isolated from culture su pernatant fluid by ammonium sulphate precipitation. The isolated haema gglutinin did not cause direct agglutination of erythrocytes. However, binding of the haemagglutinin to rabbit erythrocytes could be visuali zed by agglutination of haemagglutinin-treated erythrocytes by specifi c antiserum obtained by absorption. Western blotting showed that the h aemagglutinin obtained from erythrocyte lysates contained an antibody- reactive band with a molecular mass of 43 kDa. Haemagglutination-posit ive strains adhered to HeLa cells in higher numbers than did haemagglu tination-negative strains. The HeLa cell adherence of Group B streptoc occi was inhibited in the presence of isolated haemagglutinin or of sp ecific antiserum against the haemagglutinin. These observations sugges t that the haemagglutinating adhesins of bovine group B streptococcal isolates are directly involved in the adherence mechanisms of these or ganisms.