Immune response of swine vaccinated with a group E Streptococcus whole-culture bacterin

Swine (n = 10) were given a concentrated whole-culture adsorbate bacterin made from group E Streptococcus (GES). Two doses of bacterin were given subcutaneously 3 weeks apart. Control swine (n = 10) were given a blank preparation made from sterile culture medium. Swine were challenge exposed 3 weeks after the 2nd injection of bacterin by being penned continuously for 8 weeks with carrier swine infected with GES. A significant (P less than or equal to 0.009) immune response to vaccination with the bacterin was observed. Vaccinated swine, but not control swine, developed antibodies to an antiphagocytic factor (as detected with bactericidal and long-chain tests) before challenge exposure. Vaccinated swine also developed 51.2% (20 vs 41) fewer abscesses after challenge exposure than did control swine. Control swine developed a greater serologic response to challenge exposure, indicating a more extensive infection with GES.