Local Immunization of Ewes with Staphylococcal Cell and Cell-toxoid Vaccines

Abstract

SUMMARY Ewes were locally immunized 24 days before parturition with staphylococcal cell and cell-toxoid vaccines, and challenged during the subsequent lactation with approximately 1 million virulent staphylococci. After challenge, milk production was greater, the numbers of leucocytes and bacteria in milk were lower and the mastitis less severe, in immunized than non-immunized glands. Although antibody to cell wall constituents appeared to be largely responsible for the protection observed, the results also suggested that the presence of toxoid in vaccine preparations may be required for effective protection against staphylococcal mastitis. An in vitro system was used to evaluate the importance of specific antibody and other factors in scrum and whey in the elimination of bacteria by polymorphs. Preliminary results suggested that specific antibody facilitated the phagocytosis and intra-cellular killing of staphylococci by polymorphs and that complement was not an important factor in the lysis of these organisms. It is considered that the in vitro system used in the present experiments will be suitable as a screening test for monitoring the effectiveness of staphylococcal vaccines.