Agglutinating immunoglobulins to encapsulated Streptococcus bovis in bovine serum and saliva and a possible relation to feedlot bloat

Abstract

All bovine sera tested contained agglutinating immunoglobulins against encapsulated Streptococcus bovis. The immunoglobulins also were shown in predominantly parotid saliva. Cells grown in broth with added carbohydrate (sucrose) produced extracellular dextran (capsule) and were agglutinated by sera and saliva, but S. bovis cells grown in absence of carbohydrate were not agglutinated. The reacting material was established by adsorption with mono-specific anti-bovine gamma globulin to be an immunoglobulin. Sephadex adsorption studies showed the immunoglobulin specific to extracellular dextran. Sephadex adsorption also provided a way to isolate these immunoglobulins. Purified capsular dextran demonstrated a precipitin reaction with serum and saliva preparations. Because S. bovis capsule has been implicated in feedlot bloat, it is possible that antibodies reaching the rumen in bovine saliva may affect bloat.