A model of the internal transmission of <i>S</i>. <i>aureus</i>.

<p>With a high inoculum the host is rapidly overwhelmed by a systemic infection. With a moderate inoculum a more dynamic infection occurs. Injected <i>S</i>. <i>aureus</i> travels through the vasculature. Bacteria are then phagocytosed by the Kupffer cells (liver macrophages), with resulting containment and killing. However a few <i>S</i>. <i>aureus</i> survive and are able to form viable extracellular microlesions. Local neutrophils are recruited to aid in their control. As the abscess develops some <i>S</i>. <i>aureus</i> can likely escape into the blood. <i>S</i>. <i>aureus</i> can then seed the kidneys that can then go on to form large clonal abscesses. If both macrophages and neutrophils are unsuccessful in clearing the infection in the liver then clonal abscesses can also form there.</p

Correlation between initial inoculum, final organ clonality and survival in the mouse survival model.

<p>There is a statistically significant correlation between increasing inocula, decreasing organ clonality and decreasing survival. (A) The correlation between starting dose and final organ clonality. (B) The correlation between the proportion of mice that need culling by day 4 and organ clonality.</p

The dynamics of <i>Staphylococcus aureus</i> abscesses within a kidney organ.

<p>(A) The left kidney after dissection and before sectioning showing the multilobed abscesses throughout the kidney. (B) Schematic showing how a kidney was sectioned in order to determine the distribution of S. aureus throughout the organ both through histology (Sections F and G) and CFU determination (Section D). (C) Representative image of an <i>S</i>. <i>aureus</i> mCherry abscess. Scale bar: 100μm (D) CFU derived from homogenised sections show that the <i>S</i>. <i>aureus</i> is spatially segregated within infected organs and is unevenly distributed. (E) Representative image of <i>S</i>. <i>aureus</i> GFP abscesses. mCherry and GFP <i>S</i>. <i>aureus</i> are very infrequently found together. Scale bar: 200μm. (F) Fluorescent images showing the GFP tagged <i>S</i>. <i>aureus</i> in histology sections corresponding to the CFU sections. Scale bar: 3mm. (G) The corresponding H and E stained sections showing the abscesses. Scale bar: 3mm. (H) Summary lightsheet microscopy image of a cleared kidney abscess caused by <i>S</i>. <i>aureus</i> GFP. Scale bar: 100μm.</p

Population evenness (PE) in zebrafish declines over time.

<p>Embryos were infected with a 1:1:1 mix of the antibiotic resistance tagged variants. The proportions in each dead fish were analysed and the population evenness determined. (A) Population evenness over the time course of the experiment for USA300. At each time point the following numbers of zebrafish embryos were removed due to reaching severity limits: 20hrs: 49, 28hrs:20, 44hrs:9, 52hrs:8, 68hrs:8, 76hrs:2, 90hrs:1. (B) Population evenness over the time course of the experiment for Newman. PE of 1 is a balanced mixed population whilst PE of 0 is clonal. At each time point the following numbers of zebrafish embryos were removed due to reaching severity limits: 20hrs: 49, 28hrs:6, 44hrs:15, 52hrs:6, 68hrs:9, 76hrs:3, 90hrs:4. Line: mean linear regression. Linear regression, USA300: P<0.0001, F = 57.39, R² = 0.3766, Newman: p = 0.0006, F = 13.69, R² = 0.2504.</p

NewHG <i>S</i>. <i>aureus</i> distribution at different time points during the mouse sepsis model.

<p>Mice were infected with a 1:1:1 mixture of 3 resistance marker tagged NewHG variants and 5 mice sacrificed at each time point. (A) The proportions of each strain at each time point in the different organs in each mouse. TetR, EryR and KanR populations are blue, red and green respectively. The number in each pie chart represents the log amount of bacteria present (e.g. 10⁻⁶ CFU = 6). T.O.D: Time of Death, M.N: Mouse Number. (B) The CFU load at each time point for the organs and total CFU. Organs with CFU counts below the limit of detection (<100CFU) are represented by open circles. Error bars: mean±SD. 5 mice were sacrificed at 2hrs, 18hrs, 48hrs and 72hrs post injection of <i>S</i>. <i>aureus</i>.</p

<i>S</i>. <i>aureus</i> distribution at different time points during the mouse survival challenge model.

<p>Mice were infected with a 1:1:1 mixture of 3 resistance marker tagged NewHG variants and 5 mice sacrificed as they reached the severity limits. (A) The proportions of each strain at each time point in the different organs in each mouse. The number in each represents the log amount of bacteria (e.g. 10⁻⁶ CFU = 6). T.O.D: Time of Death, M.N: Mouse Number. (B) The CFU load at each time point for the organs and total CFU as well as the survival curve. On each day the following numbers of mice were sacrificed due to reaching severity limits: Day 2:5, Day 3:12, Day 4:3. On Day 4 for the right kidney, 2 of the data points are overlapping.</p

Effect of neutrophil or macrophage depletion on population dynamics during infection.

<p>Mice were treated with anti-Ly6G antibodies (neutrophil depletion) or clodronate liposomes (macrophage depletion). The bacteria were found primarily in the liver. (A) The population evenness of the bacteria in individual livers. (B) The CFU in individual livers. Error bars: mean ± SD. (C) The proportions of each strain in the various organs in macrophage depleted (clodronate treated) mice. (D) The proportions of each strain in the various organs in neutrophil depleted (anti-Ly6G treated) mice. All mice were sacrificed 3 days post infection. M.N: Mouse Number.</p

Flt3-L levels in synovial fluids and sera of RA patients and of control subjects.

<p>Median displayed in the horizontal line. RA serum (n = 130, median 80, range (min 0–max 3320), RA SF (n = 130, median 160 pg/ml, range (min 20–max 1980), control subjects serum (n = 70, median 70.5 pg/ml, range (min 0–max 160), and control subjects SF (n = 37, median 120 pg/ml, range (min 0–max 360).</p

Figure 2

<p>A. Balb/C mouse knee joint 30 days following intra-articular transfer of cells overexpressing Flt3-L. Arrows indicate bone erosions. Abbreviations: C = cartilage, M = meniscus, S = synovitis. B. Balb/C mouse knee joint 30 days following intra-articular transfer of cells not overexpressing Flt3-L. Abbreviations: C = cartilage, JC = joint cavity, M = meniscus, ST = synovial tissue.</p

Clinical data regarding 130 RA-patients and 103 controls participating in the study.

*<p>N.A. = not analyzed.</p