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Objective 1. Characterization of host mechanisms associated with mastitis susceptibility and resistance. <P>
Objective 2. Characterization and manipulation of virulence factors of mastitis pathogens for enhancing host defenses. <P> Objective 3. Assessment and application of new technologies that advance mastitis control, milk quality and dairy food safety. <P>Results will be disseminated through presentations at National meetings and through peer-reviewed journals, proceedings, abstracts, book chapters, theses, and extension publications. <P>Expected Outcomes. Identification of candidate genes will continue throughout this project. The marker genes will be evaluated to determine their association with mastitis resistance or susceptibility. Continued identification of mastitis susceptible cows and cow families will provide a resource for evaluating gene function and marker selection. A better understanding of cellular and nonspecific host mechanisms will provide insight into potential technologies to control mastitis. This may eventually provide effective non-antibiotic approaches to the treatment and control of mastitis. A better understanding of the genetic determinants of adhesion and invasion in environmental streptococci and E. coli may eventually allow these genetic factors to be targeted for vaccination. A better understanding of the epidemiology of streptococcal, staphylococcal, enterococcal, Klebsiella and E. coli mastitis will allow targeted control strategies to be designed and validated. New technologies such as vaccines and targeted treatment protocols will be devised and field-tested.
NON-TECHNICAL SUMMARY: The dairy industry contributes in excess of 65 billion dollars per year to the US economy, and provides jobs for over 1 million Americans. The single most costly disease of dairy cattle and a major monetary drain on the dairy industry is bovine mastitis. Mastitis is an inflammation of the mammary gland almost always associated with bacterial infection. Mastitis affects every dairy farm and approximately 38% of dairy cows in the United States. While significant advances have been made in controlling some types of mastitis, the complex etiology of the disease and ongoing changes in dairy practices dictate that new and more effective methods for control and treatment be developed over time. The goals of this project are to identify cow-based factors that contribute to disease susceptibility, identify bacterial factors that promote their ability to cause infection, and assess/apply new technologies aimed at controlling mastitis. Based upon this knowledge, we expect to improve dairy cow health and milk quality which will lead to greater profitability and consumer food safety. <P>
APPROACH: Objective 1. The dairy cows ability to defend itself against mammary infection relies upon the responsiveness of mammary epithelial cells that line the gland and first interact with invading bacteria and neutrophils which rapidly migrate to the gland upon infection to destroy invading pathogens. Using a combination of in vivo and in vitro challenge models, gene activation by mammary epithelial cells and neutrophils to Escherichia coli, Klebsiella pneumoniae, and Streptococcus uberis will be assessed through microarrays and quantitative RTPCR. Using this knowledge and that generated from the literature, candidate genes will be identified and assessed for their role as biomarkers and genetic markers of mastitis. Ongoing research will continue to assess the biological basis for increased susceptibility of cows with the CXCR1 genetic marker by evaluating cellular movement and activation of the cellular proteome via MSMS chromatography. <P>Objective 2. To establish a mammary infection, bacteria must adapt to the mammary environment and express a series of growth and virulence factors that enable it to cause infection. Our group will continue its work with S. uberis virulence factors by identifying the presence, functional activity, and immunization potential of candidate genes. This includes the previously identified S. uberis adhesion molecule (SUAM) and potential genes/proteins identified through screening a S. uberis chromosomal mutant library. The impact of mammalian stress hormones on the activation and expression of growth and virulence genes of major mastitis pathogens also will be assessed through a combination of in vitro functional assays, gene regulation via microarrays, subtractive hybridization, or quantitative RTPCR. The epidemiology of various mastitis pathogens such as coagulase negative staphylococci, Staphylococcus aureus, E. coli, S. uberis, etc will be evaluated through a combination of conventional and molecular techniques. This analysis will assess different genetic backgrounds within a species or group of bacteria and its association with severity of infection. <P>Objective 3. Tennessee will continue to evaluate and assess methodologies to control S. uberis and other forms of mastitis. Researchers also will work towards developing a risk based system to gather relevant data on the epidemiology of food-borne pathogens for the identification of critical control points during harvesting and storing raw milk.