pyrophosphate and Bacterial-Infections

Bacteria inhabit diverse environmental niches and consequently must modulate their metabolism to adapt to stress. The nucleotide second messengers guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp) (collectively referred to as (p)ppGpp) are essential for survival during nutrient starvation. (p)ppGpp is synthesized by the RelA-SpoT homologue (RSH) protein family and coordinates the control of cellular metabolism through its combined effect on over 50 proteins. While the role of (p)ppGpp has largely been associated with nutrient limitation, recent studies have shown that (p)ppGpp and related nucleotides have a previously underappreciated effect on different aspects of bacterial physiology, such as maintaining cellular homeostasis and regulating bacterial interactions with a host, other bacteria, or phages. (p)ppGpp produced by pathogenic bacteria facilitates the evasion of host defenses such as reactive nitrogen intermediates, acidic pH, and the complement system. Additionally, (p)ppGpp and pyrophosphorylated derivatives of canonical adenosine nucleotides called (p)ppApp are emerging as effectors of bacterial toxin proteins. Here, we review the RSH protein family with a focus on its unconventional roles during host infection and bacterial competition.

Topics: Animals; Bacteria; Bacterial Infections; Bacterial Physiological Phenomena; Bacterial Proteins; Diphosphates; Gene Expression Regulation, Bacterial; Humans; Nucleotides; Phosphorylation; Stress, Physiological

Topics: Acidosis, Renal Tubular; Bacterial Infections; Citrates; Crystallization; Cystinuria; Diphosphates; Female; Gastrointestinal Diseases; Humans; Hypercalcemia; Hyperparathyroidism; Magnesium; Male; Metabolism, Inborn Errors; Mucoproteins; Oxalates; Quaternary Ammonium Compounds; Sarcoidosis; Solubility; Uric Acid; Urinary Calculi; Vitamin D; Xanthine Oxidase

Rapid identification of the causative bacteria of sepsis in patients can contribute to the selection of appropriate antibiotics and improvement of patients' prognosis. Genotypic identification is an emerging technology that may provide an alternative method to, or complement, established phenotypic identification procedures. We evaluated a rapid protocol for bacterial identification based on PCR and pyrosequencing of the V1 and V3 regions of the 16S rRNA gene using DNA extracted directly from positive blood culture samples. One hundred and two positive blood culture bottles from 68 patients were randomly selected and the bacteria were identified by phenotyping and pyrosequencing. The results of pyrosequencing identification displayed 84.3 and 64.7 % concordance with the results of phenotypic identification at the genus and species levels, respectively. In the monomicrobial samples, the concordance between the results of pyrosequencing and phenotypic identification at the genus level was 87.0 %. Pyrosequencing identified one isolate in 60 % of polymicrobial samples, which were confirmed by culture analysis. Of the samples identified by pyrosequencing, 55.7 % showed consistent results in V1 and V3 targeted sequencing; other samples were identified based on the results of V1 (12.5 %) or V3 (31.8 %) sequencing alone. One isolate was erroneously identified by pyrosequencing due to high sequence similarity with another isolate. Pyrosequencing identified one isolate that was not detected by phenotypic identification. The process of pyrosequencing identification can be completed within ~4 h. The information provided by DNA-pyrosequencing for the identification of micro-organisms in positive blood culture bottles is accurate and could prove to be a rapid and useful tool in standard laboratory practice.

Topics: Bacteria; Bacterial Infections; Bacteriological Techniques; Base Sequence; Candida albicans; Candidiasis; Diphosphates; DNA, Bacterial; DNA, Fungal; DNA, Ribosomal; Gene Expression Regulation, Bacterial; Humans; Polymerase Chain Reaction; RNA, Bacterial; RNA, Ribosomal, 16S; Sepsis; Sequence Analysis, DNA; Species Specificity

Human blood Vγ9/Vδ2 T cells, monocytes and neutrophils share a responsiveness toward inflammatory chemokines and are rapidly recruited to sites of infection. Studying their interaction in vitro and relating these findings to in vivo observations in patients may therefore provide crucial insight into inflammatory events. Our present data demonstrate that Vγ9/Vδ2 T cells provide potent survival signals resulting in neutrophil activation and the release of the neutrophil chemoattractant CXCL8 (IL-8). In turn, Vγ9/Vδ2 T cells readily respond to neutrophils harboring phagocytosed bacteria, as evidenced by expression of CD69, interferon (IFN)-γ and tumor necrosis factor (TNF)-α. This response is dependent on the ability of these bacteria to produce the microbial metabolite (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP), requires cell-cell contact of Vγ9/Vδ2 T cells with accessory monocytes through lymphocyte function-associated antigen-1 (LFA-1), and results in a TNF-α dependent proliferation of Vγ9/Vδ2 T cells. The antibiotic fosmidomycin, which targets the HMB-PP biosynthesis pathway, not only has a direct antibacterial effect on most HMB-PP producing bacteria but also possesses rapid anti-inflammatory properties by inhibiting γδ T cell responses in vitro. Patients with acute peritoneal-dialysis (PD)-associated bacterial peritonitis--characterized by an excessive influx of neutrophils and monocytes into the peritoneal cavity--show a selective activation of local Vγ9/Vδ2 T cells by HMB-PP producing but not by HMB-PP deficient bacterial pathogens. The γδ T cell-driven perpetuation of inflammatory responses during acute peritonitis is associated with elevated peritoneal levels of γδ T cells and TNF-α and detrimental clinical outcomes in infections caused by HMB-PP positive microorganisms. Taken together, our findings indicate a direct link between invading pathogens, neutrophils, monocytes and microbe-responsive γδ T cells in early infection and suggest novel diagnostic and therapeutic approaches.

Topics: Adult; Antigen-Presenting Cells; Bacteria; Bacterial Infections; Cell Communication; Cell Differentiation; Cell Survival; Cells, Cultured; Diphosphates; Humans; Interferon-gamma; Interleukin-8; Lymphocyte Activation; Monocytes; Neutrophil Activation; Neutrophils; Peritonitis; Phagocytosis; Receptors, Antigen, T-Cell, gamma-delta; T-Lymphocyte Subsets; Tumor Necrosis Factor-alpha

Vgamma9/Vdelta2 T cells are a minor subset of T cells in human blood and differ from other T cells by their immediate responsiveness to microbes. We previously demonstrated that the primary target for Vgamma9/Vdelta2 T cells is (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP), an essential metabolite produced by a large range of pathogens. Here we wished to study the consequence of this unique responsiveness in microbial infection. The majority of peripheral Vgamma9/Vdelta2 T cells shares migration properties with circulating monocytes, which explains the presence of these two distinct blood cell types in the inflammatory infiltrate at sites of infection and suggests that they synergize in anti-microbial immune responses. Our present findings demonstrate a rapid and HMB-PP-dependent crosstalk between Vgamma9/Vdelta2 T cells and autologous monocytes that results in the immediate production of inflammatory mediators including the cytokines interleukin (IL)-6, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, and oncostatin M (OSM); the chemokines CCL2, CXCL8, and CXCL10; and TNF-related apoptosis-inducing ligand (TRAIL). Moreover, under these co-culture conditions monocytes differentiate within 18 hours into inflammatory dendritic cells (DCs) with antigen-presenting functions. Addition of further microbial stimuli (lipopolysaccharide, peptidoglycan) induces CCR7 and enables these inflammatory DCs to trigger the generation of CD4(+) effector alphabeta T cells expressing IFN-gamma and/or IL-17. Importantly, our in vitro model replicates the responsiveness to microbes of effluent cells from peritoneal dialysis (PD) patients and translates directly to episodes of acute PD-associated bacterial peritonitis, where Vgamma9/Vdelta2 T cell numbers and soluble inflammatory mediators are elevated in patients infected with HMB-PP-producing pathogens. Collectively, these findings suggest a direct link between invading pathogens, microbe-responsive gammadelta T cells, and monocytes in the inflammatory infiltrate, which plays a crucial role in the early response and the generation of microbe-specific immunity.

Topics: Antigen-Presenting Cells; Bacterial Infections; Cell Communication; Cell Differentiation; Cell Survival; Cells, Cultured; Cytokines; Data Interpretation, Statistical; Diphosphates; Humans; Inflammation; Monocytes; Peritoneal Cavity; Peritoneal Dialysis; Peritonitis; Receptors, Antigen, T-Cell, gamma-delta; T-Lymphocyte Subsets

gammadelta T cells comprise an evolutionarily conserved yet poorly understood subset of T cells. Numerous features place these unconventional lymphocytes at the branching point between antigen-presenting cells and natural killer cells of the innate immune system and major-histocompatibility-complex-restricted alphabeta T cells of the adaptive immune system. We propose a role for human Vgamma9/Vdelta2 T cells in the generation of monocyte-derived inflammatory dendritic cells during infection. Our model incorporates the peculiar innate-like specificity of Vgamma9/Vdelta2 T cells for the microbial metabolite (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP), co-recruitment of monocytes and Vgamma9/Vdelta2 T cells to sites of infection, and their crosstalk, with profound consequences for the initiation of antigen-specific alphabeta T-cell responses. Vgamma9/Vdelta2 T cells act thus as a cellular switch between innate and adaptive defence mechanisms.

Topics: Adaptive Immunity; Bacterial Infections; Cell Communication; Cell Differentiation; Dendritic Cells; Diphosphates; Humans; Immunity, Innate; Monocytes; Receptors, Antigen, T-Cell, gamma-delta; T-Cell Antigen Receptor Specificity; T-Lymphocytes

Scintigraphic exploration of the sacroiliac (S.I.) joints by 99 m-technetium pyrophosphate is simple and free of all danger. The fixation of the isotope in the right sacroiliac (R.S.I.) and the "normal" limits of the fixation ratios R.S.I./L.R. and the lumbar rachis (L.R.), visible on the same film. A series of 28 controls having made it possible to calculate the "normal" limits of the fixation ratios R.S.I./L.R. and L.S.I./L.R., the isotopic fixation was measured in 25 patients with sacroiliac inflammation, 21 of whom were rheumatic, 3 infectious. It was shown that scintigraphy could yield useful information on the evolution of sacroiliac inflammation, making an early diagnosis possible, and also contributing to differentiation between rheumatic and infectious inflammation.

Topics: Adult; Aged; Arthritis, Reactive; Back Pain; Bacterial Infections; Bone and Bones; Diphosphates; Female; Humans; Ilium; Joint Diseases; Male; Middle Aged; Osteoarthritis; Psoriasis; Radionuclide Imaging; Rheumatic Diseases; Sacroiliac Joint; Sacrum; Spinal Diseases; Spondylitis, Ankylosing; Staphylococcal Infections; Technetium; Tuberculosis, Spinal