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Title: ESCHERICHIA COLI AND STAPHYLOCOCCUS AUREUS ELICIT DIFFERENTIAL INNATE IMMUNE RESPONSES FOLLOWING INTRAMAMMARY INFECTION

Author
item Bannerman, Douglas
item Paape, Max
item LEE, JAI-WEI - MCGILL UNIVERSITY CANADA
item ZHAO, XIN - MCGILL UNIVERSITY CANADA
item HOPE, JAYNE - UNITED KINGDOM
item RAINARD, PASCAL - FRANCE

Submitted to: Clinical and Diagnostic Laboratory Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2004
Publication Date: 5/1/2004
Citation: Bannerman, D.D., Paape, M.J., Lee, J., Zhao, X., Hope, J.C., Rainard, P. 2004. Escherichia coli and staphylococcus aureus elicit differential innate immune responses following intramammary infection. Clinical and Diagnostic Laboratory Immunology. vol. 11(3), pp. 463-72.

Interpretive Summary: Escherichia coli and Staphylococcus aureus are the most prevalent environmental and contagious mastitis pathogens, respectively. E. coli infection is often characterized by a limited acute inflammatory course, whereas, S. aureus infection frequently leads to a chronic infectious state. The ability of bacteria to establish infection is due to both intrinsic properties of the pathogen and the effectiveness of the immune response to the bacteria. This study increases our understanding of mammary host defense mechanisms to E. coli or S. aureus and identifies both common and divergent innate immune responses elicited by these bacteria.

Technical Abstract: Staphylococcus aureus and Escherichia coli are among the most prevalent species of Gram-positive and Gram-negative bacteria, respectively, that induce clinical mastitis. The innate immune system comprises the immediate host defense mechanisms to protect against infection and contributes to the initial detection of and pro-inflammatory response to infectious pathogens. The objective of the current study was to characterize the differential innate immune response to experimental intramammary infection with E. coli and S. aureus. The cytokine response and changes in the levels of soluble CD14 (sCD14) and lipopolysaccharide (LPS)-binding protein (LBP), two proteins that contribute to host recognition of bacterial cell wall products, were studied. Intramammary infection with either E. coli or S. aureus elicited systemic changes including decreased milk output, a febrile response, and induction of the acute phase synthesis of LBP. Infection with either bacteria resulted in increased milk levels of IL-1 beta, IFN-gamma, IL-12, sCD14, and LBP. High levels of the complement cleavage product C5a, and the anti-inflammatory cytokine IL-10, were detected at several time points following E. coli infection, whereas, S. aureus infection elicited a slight detectable increase in these mediators at a single time point. Increases in IL-8 and TNF-alpha were only observed in quarters infected with E. coli. Together, these data demonstrate the variability of the host innate immune response to E. coli and S. aureus and suggest that the limited cytokine response to S. aureus may contribute to the well-know ability of this bacterium to establish chronic intramammary infection.