Leucocytic changes in cows given intravenous injections of Escherichia coli endotoxin

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

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.

Metabolic, endocrine and haematological responses to intravenous E. coli endotoxin administration in 1-week-old calves

Responses to i.v. injected E. coli endotoxin (E), followed by saline infusion, as compared with saline infusion alone, were studied for 24 h in 1-week-old calves. After administration of E, respiratory rate (RR), heart rate (HR), rectal temperature (RT), serum iron, insulin, (I), cortisol and tumor necrosis factor-alpha, transiently, and urea, continuously, increased. Isoleucine and leucine became elevated at 24 h, whereas white-blood-cell number, free fatty acids (FFA) and triglycerides (TG) increased after an initial fall. After administration of E, packed-cell volume, erythrocyte number, haemoglobin, glucose (G), cholesterol, phospholipids (PL), lysine, arginine, proline, citrulline, calcium (Ca), inorganic phosphorus, insulin-like growth factor I (IGF-I) and 3,5,3'-triiodothyronine (T3) concentrations and alkaline phosphatase (AP) and gamma-glutamyl transferase (gamma GT) activities increased significantly while growth hormone decreased non-significantly. When saline was infused alone, G, TG, PL, Ca, AP, gamma GT, I, IGF-I and T3 decreased, while FFA, urea and sodium increased, but, changes of G, urea, AP, IGF-I and T3 were less marked than after injection of E. Potassium, total protein and albumin concentrations, and glutamyl dehydrogenase and glutamate oxalacetate transaminase activities were not significantly affected by either treatment. In conclusion, metabolic and endocrine changes during saline infusion alone were typical for food withdrawal. Changes of variables after administration of E were transient, biphasic or sustained, thus expressing complex interactions between metabolic parameters, endocrine factors and cytokines.