46 research outputs found

    No difference in <i>B. pseudomallei</i> phagocytosis or killing capacity between WT and MyD88 KO cells.

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    <p>(A) Peripheral blood neutrophils were incubated at 37°C with CFSE-labeled growth-arrested <i>B. pseudomallei</i> (1×10<sup>7</sup> CFU/ml) after which time-dependent phagocytosis was quantified; 1×10<sup>4</sup> neutrophils were analysed per sample (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003494#s2" target="_blank">Methods</a> section). (B) Killing capacity of peritoneal macrophages are shown as percentage of killed <i>B. pseudomallei</i> compared to t = 0. Data are mean±SEM; n = 5 per mouse strain. Open rounds represent WT cells, while black squares represent MyD88 KO mice; ns denotes not significant.</p

    MyD88 KO mice show increased bacterial outgrowth during experimental melioidosis.

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    <p>WT and MyD88 KO mice were intranasally infected with <i>B. pseudomallei</i> (5×10<sup>2</sup> CFU). Bacterial loads were measured 24 h and 72 h after inoculation in lungs (A), liver (B) and blood (C). Data are mean±SEM (n = 6–7 per group at each time point). ** <i>P</i><0.01.</p

    MyD88 KO, but not TRIF KO, mice show an accelerated mortality during experimental melioidosis.

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    <p>Survival of wild-type (WT, open rounds) and MyD88 KO mice (black squares) (A) or TRIF mutant (black squares) mice (B) intranasally infected with 5×10<sup>2</sup> CFU <i>B. pseudomallei</i>. Mortality was assessed twice daily for one week. n = 8–10 per group; ns denotes not significant; <i>P</i> value indicates the difference between MyD88 KO and WT mice.</p

    Effect of MyD88 deficiency on total and differential lung cell counts.

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    <p>Total leukocyte counts (×10<sup>5</sup>/ml) and differential cell counts in lungs of wild-type (WT) and MyD88 knock-out mice 24 hours after intranasal infection with 5×10<sup>2</sup> CFU of <i>B. pseudomallei</i>. Data are mean±SEM (n = 6–7/group); ** <i>P</i><0.01 versus WT.</p

    Dissemination of <i>S.</i> Typhi during systemic infection.

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    <p>Typhoid is usually contracted by ingestion of food or water contaminated by fecal or urinary carriers excreting <i>S.</i> Typhi. The incubation period is usually 7 to 14 d. In the small intestine the bacteria adhere to the mucosa and then invade the epithelial cells. The Peyer's patches, which are aggregrated lymphoid nodules of the terminal ileum, play an important role in the transport to the underlying lymphoid tissue. Specialized epithelial cells such as M cells overlying these Peyer's patches are probably the site of internalization of <i>S.</i> Typhi. Once the bacteria have penetrated the mucosal barrier, the invading organism translocates to the intestinal lymphoid follicles and the draining mesenteric lymph nodes, and some pass on to the reticuloendothelial cells of the liver and spleen. During the bacteremic phase, the bacteria are widely disseminated throughout the body. Secondary infection can occur with liver, spleen, bone-marrow, gallbladder, and Peyer's patches as the most preferred sites. The gallbladder is the main reservoir during a chronic infection with <i>S.</i> Typhi and invasion occurs either directly from the blood or by retrograde spread from the bile. Of interest, the ability of <i>Salmonella</i> to form biofilms on gallstones is likely to be a critical factor in establishment of chronic carriage and shedding of <i>S.</i> Typhi <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002933#ppat.1002933-Crawford1" target="_blank">[88]</a>. The bacteria that are excreted in the bile can then reinvade the intestinal wall by the mechanism previously described or are excreted by feces. Typical clinical symptoms are fever, malaise, and abdominal discomfort. Clinical features such as a tender abdomen, hepatomegaly, splenomegaly, and a relative bradycardia are common. Rose spots, the classical skin lesions associated with typhoid fever, are relatively uncommon and occur in 5%–30% of cases. The most severe manifestations of typhoid leading to sepsis and death are either necrosis of the Peyer's patches resulting in gut perforation and peritonitis or a toxic encephalopathy associated with myocarditis and haemodynamic shock <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002933#ppat.1002933-Parry1" target="_blank">[8]</a>, <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002933#ppat.1002933-Everest1" target="_blank">[89]</a>.</p

    MyD88 plays an important role in early neutrophil recruitment after infection with <i>B. pseudomallei</i>.

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    <p>The impact of MyD88 deficiency on early neutrophil recruitment was investigated by analysing the amount of neutrophils in the pulmonary compartment using FACS analysis (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003494#s2" target="_blank">Methods</a>) 24 h after intranasal inoculation of WT and MyD88 KO mice with 5×10<sup>2</sup> CFU <i>B. pseudomallei</i>. MyD88 KO mice displayed significantly fewer neutrophils in their lungs compared with WT mice (the percentages of neutrophils of the total pulmonary cell count are given from one respresentative WT and one respresentative MyD KO mouse) (A). Additionally, MyD88 deficient neutrophils (gray line and gray bars) present at t = 24 expressed less CD11b on their surface compared to WT neutrophils (black line and white bars): representative histograms show decreased CD11b expression on pulmonary neutrophils (B). This corresponded with lower MPO levels in lung homogenates of MyD88 KO mice (gray bars) compared to controls (white bars) (C). In line, pulmonary MIP-2 (D) and KC (E) levels tended to be lower or were significantly reduced in MyD88 KO mice. LIX levels were unaltered in MyD88 KO mice at this early time point (F). SSC, side scatter; FITC: fluorescein isothiocyanate; PE, phycoerythrin; MFI, mean fluorescence intensity; MPO, Myeloperoxidase; MIP-2: macrophage-inflammatory protein-2; LIX, lipopolysaccharide-induced CXC chemokine. Bar figures represent mean±SEM; n = 6–8 per mouse strain. * <i>P</i><0.05; ** <i>P</i><0.01.</p

    <i>Salmonella</i> and its first encounter with the host.

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    <p>(a) The intracellular life of <i>Salmonella</i>. Invasion of phagocytic and non-phagocytic cells. <i>Salmonella</i> is a facultative intracellular pathogen that can be found in a variety of phagocytic and non-phagocytic cells, in which it is able to survive and replicate. To establish this intracellular niche, the T3SS1 and -2 play a predominant role; key virulence factors are involved in accessing and utilizing these cells <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002933#ppat.1002933-Ibarra1" target="_blank">[36]</a>. After ingestion, intestinal colonization follows and <i>Salmonella</i> enters enterocytes and dendritic cells in the intestinal epithelium <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002933#ppat.1002933-Ibarra1" target="_blank">[36]</a>. Subsequently, <i>Salmonella</i> that reach the submucosa can be internalized by resident macrophages via different mechanisms: by phagocytosis, active invasion using the T3SS1 or T3SS1-independent invasion using fimbriae or other adhesins on the bacterial surface. (1) <i>Salmonella</i>-containing-vacuole. Following internalization <i>Salmonella</i> remains within a modified phagosome known as the <i>Salmonella</i> containing vacuole (SCV) and injects a limited number of effector proteins, such as SipA, SipC, SopB/SigD, SodC-1, SopE2, and SptP into the cytoplasm. These effectors cause rearrangements of the actin cytoskeleton and SCV morphology among other changes. (2) Replication within the SCV. <i>Salmonella</i> survives and replicates within the SCV, where it is able to avoid host antimicrobial effector mechanisms. The T3SS2 is required for systemic virulence in the mouse and survival within macrophages. (3) Transport of <i>Salmonella</i> to distant sites. After penetration of the M cells, the invading microorganisms translocate to the intestinal lymphoid follicles and the draining mesenteric lymph nodes, and some pass on to the reticuloendothelial cells of the liver and spleen. <i>Salmonella</i> organisms are able to survive and multiply within the mononuclear phagocytic cells of the lymphoid follicles, liver, and spleen <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002933#ppat.1002933-Ibarra1" target="_blank">[36]</a>. (b) Host–pathogen interaction in typhoid and non-typhoid <i>Salmonella</i>. Simplified scheme of the first encounter between <i>Salmonella</i> spp. and the immune system. Specified cells such as neutrophils, macrophages, dendritic, phagocytic, and epithelial cells recognize specific pathogen associated molecular patterns (PAMPs) and danger-associated-molecular patterns (DAMPs), thereby eliciting an immune response. PAMPs such as LPS, Flagella, and bacterial DNA can trigger TRL4, TRL5, and TRL9, respectively. TLR-induced activation of NF-κB is essential for the production of pro-IL-1β, pro-IL-18, which can be negatively regulated by IRAK-M <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002933#ppat.1002933-Kobayashi1" target="_blank">[90]</a>. The NLRs are situated in the cytosol and can also recognize PAMPs. However, NLRP3 is triggered by a different, yet unknown, mechanism, although DAMPs are thought to play a crucial role. TLR, toll-like receptors; LPS, lipopolysaccharide; NF-κB, regulated nuclear factor kappa-light-chain-enhancer of activated B cells; IRAK-M, IL-1R-assiociated kinase-M; IL, Interleukin; ASC, apoptotic speck protein containing a caspase recruitment domain; NLR, NOD-like receptors (including NLRP3 and NLRC4); MyD88, myeloid differentiation primary response gene <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002933#ppat.1002933-Crawford1" target="_blank">[88]</a>.</p

    International journal of antimicrobial agents

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    <p><b>VWF propeptide concentrations are elevated in melioidosis (A) and correlate with VWF antigen levels (B), but do not correlate with mortality (C).</b> VWF = von Willebrand factor. The data from 34 melioidosis patients (of whom 12 died) and 52 controls are presented as box plots with Tukey whiskers showing the smallest observation, lower quartile, median, upper quartile and largest observation. ***<i>P</i> <0.001 for the difference between patients and controls; (Student’s t-test); <i>P</i> = 0.21 for the difference between survivors (n = 22) and non-survivors (n = 12). For the scatter plot, each dot represents a single study subject from the patient group only (n = 34); the correlation coefficient and <i>*P</i> <0.05 reported are for Pearson’s <i>r</i>. The corresponding regression line for the scatter plot is drawn in bold, with the 95% confidence interval for the regression line marked by interrupted lines.</p
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