Escherichia coliandStaphylococcus aureusElicit Differential Innate Immune Responses following Intramammary Infection

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 proinflammatory response to infectious pathogens. The objective of the present study was to characterize the different innate immune responses to experimental intramammary infection with E. coli and S. aureus during clinical mastitis. The cytokine response and changes in the levels of soluble CD14 (sCD14) and lipopolysaccharide-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 bacterium resulted in increased levels of interleukin 1␤ (IL-1␤), gamma interferon, IL-12, sCD14, and LBP in milk. 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 but detectable increase in these mediators at a single time point. Increases in IL-8 and tumor necrosis factor alpha were observed only 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-known ability of the bacterium to establish chronic intramammary infection.

Morphometric analysis of proinflammatory cytokines in mammary glands of sows suggests an association between clinical mastitis and local production of IL-1beta, IL-6 and TNF-alpha

“…Possibly, in these sows there may be abundant and regulated release of anti-inflammatory mediators [40,53], limiting the production of the inflammatory cytokines. However, in accordance with our results, previous studies in cows have shown a significant increase in the proinflammatory cytokines at the level of both mRNA [33,37] and protein [6,11,26,32,45,48,54] in either mammary tissues or milk collected from the infected glands following intramammary inoculation with E. coli. The results here indicate that the development of clinical symptoms of coliform mastitis in the sow is associated with a locally increased proinflammatory cytokine production in response to intramammary E. coli infection.…”

“…For instance, it has been established that IL-1β, IL-6, IL-8, and TNF-α play a role in the initiation of the inflammatory responses following intramammary inoculation with Escherichia coli [6,45,48,59]. Analyses of biopsies collected from mammary glands of sows inoculated with E. coli demonstrated the transcription of the genes for a number of proinflammatory cytokines, but analyses of IL-6 and TNF-α in the same set of sows revealed that variations in serum/plasma concentrations were not reflected in the mRNA expression in mammary tissues [59,60].…”

Staphylococcus aureuslipoteichoic acid triggers inflammation in the lactating bovine mammary gland

“…Each one received at time zero RPMI in one quarter, 10 g LTA in another one, and 100 g LTA in a third quarter. The infused quarters were aseptically sampled just before infusion after the morning milking, then 4,8,12,16,24,32,48,72 and 96 h post-infusion. At each sampling time up to 24 h post-infusion, the rectal temperature was taken and a clinical examination was performed (appearance of gland and milk).…”

“…Milk somatic cells were counted on an automated cell counter (Fossomatic model 90; Foss Food Technology, Hillerod, Denmark) as described [4]. For the determination of the proportion of neutrophils among milk somatic cells, cytospin slides were prepared with a cytocentrifuge (Shandon Southern centrifuge, Shandon Inc, Pittsburgh, PA, USA).…”

“…To determine the concentrations of IL-1 , a sandwich ELISA making use of mouse anti-IL-1 monoclonal antibody (MAb 1D4; AbDSerotec, Oxford, UK), recombinant bovine IL-1 (AbDSerotec) and rabbit anti-bovine IL-1 (AbDSerotec) was performed as described [4,43]. The lowest level of quantification in milk was 0.10 ng/mL.…”