Effect of specific antibody on adherence of Staphylococcus aureus to bovine mammary epithelial cells

Staphylococcus aureus is a major pathogen in the bovine mammary gland. The ability of S. aureus to adhere to epithelial cells in the ductules and alveoli of the bovine mammary gland is believed to add greatly to its virulence and may be necessary for colonization. Two in vitro methods were developed for the purposes of quantifying adherence and of determining the effect which specific antibody may have in inhibiting the adherence of this organism. Both methods utilize bovine mammary epithelial primary cells as targets for labeled bacteria. In one assay, the bacteria are labeled with [methyl-3H]thymidine and incubated on the primary epithelial monolayers. The second assay involves labeling the bacteria with biotin. An enzyme-linked immunosorbent assay is then performed with streptavidin conjugated to horseradish peroxidase. Both methods have proven to be reliable and allow for the testing of many criteria in one assay. Cows were immunized with a whole-cell vaccine, and immune serum and milk were collected. The bacteria were then incubated in the presence of serum or milk as a test for antiadherent capability. By using the methods described, distinct antiadherent activity in both serum and milk was demonstrated.