Interaction between S. aureus and bovine mammary epithelial cells

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In the dairy industry, mastitis is the most costly disease that causes significant losses in economic and milk production terms. As well, mastitis is an animal welfare issue and use of antibiotics to treat mastitis is of concern for food and environmental safety. While many bacteria can cause bovine mastitis, one of the major causes is Staphylococcus aureus (S. aureus). S. aureus mastitis is contagious and extremely difficult to control because it usually develops into a chronic infection due to the ability of S. aureus to adhere, invade, and persist in mammary epithelial cells. S. aureus strains from intramammary infection produce many cell surface-associated products. The exact pathogenic roles of most of the products and their effects on adhesion and invasion are not well evaluated. It is also known that mammary epithelial cell-associated molecules interact with S. aureus during the pathogenesis of mastitis, but their roles on adhesion and invasion have not been characterized. The interaction between S. aureus and bovine mammary glands is very complex. The global objective of this proposed research is to use ClfA, a surface protein on S. aureus, as a model molecule to study the mechanisms by which surface adhesins of S. aureus attach to and invade bovine mammary epithelial cells and how epithelial cells respond to the infection. Specifically, this proposed study aims to answer the following questions: (1) How does gene expression change in both S. aureus and bovine mammary epithelial cells during their interactions? (2) How does the varying length of the repeats in ClfA from different strains or isolates of S. aureus affect the binding and invasion to mammary epithelial cells? (3) Is it possible to identify and isolate the receptors on bovine mammary epithelial cells? Results from this proposed study will shed more light on the pathogenic mechanisms of S. aureus and consequently provide new strategies for a better prevention, therapy program and management of bovine mastitis. It is not envisaged that this research will lead to any vaccine development. Nevertheless, this research program will certainly contribute to our basic understanding of the interaction between S. aureus and the bovine mammary gland.