Schematic diagram of the endocarditis model.

<p>The experimental procedure involved four stages. First, valve trauma was induced by placing a 32-G catheter (red) at the aortic root via the right carotid artery. Second, <i>S. aureus</i> bacteria were injected via the tail vain 24 h after surgery. Third, MRI was performed 48 h after surgery. Fourth, animals were euthanized after MRI, hearts and organs were removed, inspected macroscopically and processed for microbial assessment or histology. Visual inspection showed clear, translucent valves (white arrow) for non-infected hearts (top) and yellow, thickened valves (white arrow) for colonized hearts (bottom).</p

Histology of aortic valves.

<p>Gram staining (left column) revealed large colonies of Gram-positive bacteria on the valves in mice infected with (A) unlabeled bacteria, (B) labeled bacteria, and (C) labeled bacteria and additional administration of VSOP to label macrophages. Large arrows indicate where 100-fold magnifications were taken. Hematoxylin-esoin staining (right column) confirmed the presence of bacteria (red arrows), displayed neutrophil recruitment (blue arrows) and showed valve thickening due to early deposition of connective tissue, but did not show large numbers of infiltrating immune cells. Magnification, 4 fold (inset 100 fold).</p

MRI scores depend on number of infecting bacteria.

<p>Endocarditis score (A) and score for presence of intra-cardiac masses (B) for the initial group of mice infected with different concentrations of bacteria. MRI was performed 24 h after infection with <i>S. aureus</i> and scored on a six-level scale from 0 (inconspicuous) to 5 (most conspicuous). n represents the number of animals. As two independent scorings were used the number of data points per column is 2×n. Box plots show median, 25^th and 75^th percentiles and extreme values. Significant differences are indicated: * p<0.05.</p

MRI detection of <i>S. aureus</i> vegetations on the aortic valve.

<p>Exemplary long axis views of the mouse heart acquired with self-gated CINE UTE MRI (TR/TE : 5/0.31 ms, FA: 15°, resol: (125 µm)², MTX: 256×256, slice thickness: 1 mm, scan duration: 12∶08 min) show the aortic valves in closed (A–C) and open (D–F) state. Flow artifacts were almost completely suppressed by the use of self-gated UTE MRI. (A,D) Images of a mouse with sham surgery infected with unlabeled bacteria show normal valves (arrows). (B, E) In images of a catheterized mouse infected with unlabeled bacteria the catheter as well as valve thickening and an additional intracardial mass is visible (arrows). (C, F) Large hypointensities on the valves (arrows) are observed in this catheterized mouse infected with iron labeled bacteria.</p

Gram-negative and Gram-Positive Bacterial Infections Give Rise to a Different Metabolic Response in a Mouse Model

Metabolomics has become an important tool to study host-pathogen interactions and to discover potential novel therapeutic targets. In an attempt to develop a better understanding of the process of pathogenesis and the associated host response we have used a quantitative ¹H NMR approach to study the metabolic response to different bacterial infections. Here we describe that metabolic changes found in serum of mice that were infected with <i>Staphylococcus aureus</i>, <i>Streptococcus pneumoniae</i>, <i>Escherichia coli</i> and <i>Pseudomonas aeruginosa</i> can distinguish between infections caused by Gram-positive and Gram-negative bacterial strains. By combining the results of the mouse study with those of bacterial footprinting culture experiments, bacterially secreted metabolites could be identified as potential bacterium-specific biomarkers for <i>P. aeruginosa</i> infections but not for the other strains. Multivariate statistical analysis revealed correlations between metabolic, cytokine and physiological responses. In TLR4 and TLR2 knockout mice, host-response pathway correlated metabolites could be identified and allowed us for the first time to distinguish between bacterial- and host-induced metabolic changes. Since Gram-positive and Gram-negative bacteria activate different receptor pathways in the host, our results suggest that it may become possible in the future to use a metabolomics approach to improve on current clinical microbiology diagnostic methods

Philippe Lachaud, architecte et urbaniste (1935-2012)

Liver and spleen iron content from Alk3fl/fl and Alk3fl/fl; Alb-Cre mice 14 days after BA challenge. (a) Liver iron content in Alk3fl/fl and Alk3fl/fl; Alb-Cre mice 14 days after heat-killed Brucella abortus (BA) injection (*P = 0.04: Alk3fl/fl; Alb-Cre injected with saline [n = 4] vs Alk3fl/fl; Alb-Cre injected with BA [n = 6]). (b) Spleen iron content from Alk3fl/fl and Alk3fl/fl; Alb-Cre mice 14 days after heat-killed Brucella abortus (BA) injection. (TIFF 82 kb

Additional file 5: of Deficiency of the BMP Type I receptor ALK3 partly protects mice from anemia of inflammation

Liver and spleen iron content from Alk3fl/fl and Alk3fl/fl; Alb-Cre mice 14 days after BA challenge. (a) Liver iron content in Alk3fl/fl and Alk3fl/fl; Alb-Cre mice 14 days after heat-killed Brucella abortus (BA) injection (*P = 0.04: Alk3fl/fl; Alb-Cre injected with saline [n = 4] vs Alk3fl/fl; Alb-Cre injected with BA [n = 6]). (b) Spleen iron content from Alk3fl/fl and Alk3fl/fl; Alb-Cre mice 14 days after heat-killed Brucella abortus (BA) injection. (TIFF 82 kb

Additional file 1: of Deficiency of the BMP Type I receptor ALK3 partly protects mice from anemia of inflammation

Experimental design. (a) Mice were fed an iron deficient diet since weaning and throughout the experiment. At the age of 12 weeks, female Alk3fl/fl; Alb-Cre and Alk3fl/fl mice were intraperitoneally injected with 5 × 108 particles/mouse of heat-killed Brucella abortus (BA) or saline. Two weeks later blood and organs were collected. (b) 12 week old Alk3fl/fl; Alb-Cre and Alk3fl/fl female mice fed a regular diet were intravenously inoculated with 1 × 106 colony forming units (CFUs) of Staphylococcus aureus. Twenty-four hours later blood and organs were collected. (TIFF 164 kb

Additional file 2: of Deficiency of the BMP Type I receptor ALK3 partly protects mice from anemia of inflammation

Table S1. Semi-quantitative real-time PCR primer. (DOCX 15 kb

Additional file 8: of Deficiency of the BMP Type I receptor ALK3 partly protects mice from anemia of inflammation

Immunofluorescence staining of ferroportin in the duodenum of Alk3fl/fl and Alk3fl/fl; Alb-Cre mice. Ferroportin immunofluorescence staining of formalin fixed paraffin sections of the villosities of the duodenum with 20 times magnification. (Panel a) Control mice with nuclear (DAPI) and ferroportin (FITC) staining of a duodenal section. Cutout images merged (nuclear and ferroportin) and ferroportin (FITC) alone. (Panel b) Duodenal section of hepatocyte-specific Alk3 deficient mice with cutout images merged (nuclear and ferroportin) and ferroportin (FITC) alone. White arrows highlight specific FPN staining. (TIFF 3601 kb