Open Access
Vet. Res.
Volume 39, Number 2, March-April 2008
Number of page(s) 23
Published online 29 January 2008
How to cite this article Vet. Res. (2008) 39:18
Vet. Res. (2008) 39:18
DOI: 10.1051/vetres:2007057

Escherichia coli, but not Staphylococcus aureus triggers an early increased expression of factors contributing to the innate immune defense in the udder of the cow

Wolfram Petzl1, Holm Zerbe1, Juliane Günther2, Wei Yang2, 3, Hans-Martin Seyfert2, Gerd Nürnberg2 and Hans-Joachim Schuberth4

1  Clinic for Ruminants, Ludwig-Maximilians-University, Munich, Germany
2  Research Institute for the Biology of Farm Animals, Dummerstorf, Germany
3  Present address: Duke University, Durham, North Carolina, USA
4  Institute of Immunology, University of Veterinary Medicine, Hannover, Germany

(Received 3 March 2007; accepted 7 November 2007 ; published online 29 January 2008)

Abstract - The outcome of an udder infection is influenced by the pathogen species. We established a strictly defined infection model to better analyze the unknown molecular causes for these pathogen-specific effects, using Escherichia coli and Staphylococcus aureus strains previously asseverated from field cases of mastitis. Inoculation of quarters with 500 CFU of E. coli (n = 4) was performed 6 h, 12 h, and 24 h before culling. All animals showed signs of acute clinical mastitis 12 h after challenge: increased somatic cell count (SCC), decreased milk yield, leukopenia, fever, and udder swelling. Animals inoculated with 10 000 CFU of S. aureus for 24 h (n = 4) showed no or only modest clinical signs of mastitis. However, S. aureus caused clinical signs in animals, inoculated for 72 h-84 h. Real-time PCR proved that E. coli inoculation strongly and significantly upregulated the expression of $\beta$-defensins, TLR2 and TLR4 in the pathogen inoculated udder quarters as well as in mammary lymph nodes. TLR3 and TLR6 were not significantly regulated by the infections. Immuno-histochemistry identified mammary epithelial cells as sites for the upregulated TLR2 and $\beta$-defensin expression. S. aureus, in contrast, did not significantly regulate the expression of any of these genes during the first 24 h after pathogen inoculation. Only 84 h after inoculation, the expression of $\beta$-defensins, but not of TLRs was significantly (> 20 fold) upregulated in five out of six pathogen inoculated quarters. Using the established mastitis model, the data clearly demonstrate a pathogen-dependent difference in the time kinetics of induced pathogen receptors and defense molecules.

Key words: toll-like receptor / mastitis / beta-defensin / mammary epithelial cell

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© INRA, EDP Sciences 2008