Antibodies in bovine serum and lacteal secretions to capsular antigens of Staphylococcus aureus.

Pregnant cows were immunized systemically with an encapsulated strain of Staphylococcus aureus (Smith diffuse strain). Antibodies in serum and colostrum were detectable by enzyme-linked immunosorbent assay and prevented capsule production by the Smith diffuse strain in a soft agar medium. Antibody in milk, although detectable by enzyme-linked immunosorbent assay, did not affect the production of capsule in vitro. Antibodies were absorbed from milk and serum, using staphylococcal surface antigen. In a 2nd experiment, lactating cows were immunized, using Smith diffuse strain antigens in the form of a bacterin or as a surface extract; the bacterin or extract was emulsified in Freund's incomplete adjuvant. Antibody titers in the milk of cows given bacterin were significantly (P less than 0.001) greater than titers in the milk of animals immunized with surface extract. The soft agar technique was insufficiently sensitive to detect antibody in the milk of any of the cattle.