19 results on '"Travier L"'
Search Results
2. Bacterial capsular polysaccharides with antibiofilm activity share common biophysical and electrokinetic properties.
- Author
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Bernal-Bayard J, Thiebaud J, Brossaud M, Beaussart A, Caillet C, Waldvogel Y, Travier L, Létoffé S, Fontaine T, Rokbi B, Talaga P, Beloin C, Mistretta N, Duval JFL, and Ghigo JM
- Subjects
- Biofilms, Anti-Bacterial Agents pharmacology, Bacteria, Polymers, Microbial Sensitivity Tests, Polysaccharides, Bacterial chemistry, Anti-Infective Agents
- Abstract
Bacterial biofilms are surface-attached communities that are difficult to eradicate due to a high tolerance to antimicrobial agents. The use of non-biocidal surface-active compounds to prevent the initial adhesion and aggregation of bacterial pathogens is a promising alternative to antibiotic treatments and several antibiofilm compounds have been identified, including some capsular polysaccharides released by various bacteria. However, the lack of chemical and mechanistic understanding of the activity of these polymers limits their use to control biofilm formation. Here, we screen a collection of 31 purified capsular polysaccharides and first identify seven new compounds with non-biocidal activity against Escherichia coli and/or Staphylococcus aureus biofilms. We measure and theoretically interpret the electrophoretic mobility of a subset of 21 capsular polysaccharides under applied electric field conditions, and we show that active and inactive polysaccharide polymers display distinct electrokinetic properties and that all active macromolecules share high intrinsic viscosity features. Despite the lack of specific molecular motif associated with antibiofilm properties, the use of criteria including high density of electrostatic charges and permeability to fluid flow enables us to identify two additional capsular polysaccharides with broad-spectrum antibiofilm activity. Our study therefore provides insights into key biophysical properties discriminating active from inactive polysaccharides. The characterization of a distinct electrokinetic signature associated with antibiofilm activity opens new perspectives to identify or engineer non-biocidal surface-active macromolecules to control biofilm formation in medical and industrial settings., (© 2023. The Author(s).)
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- 2023
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3. Microbial and immune factors regulate brain maintenance and aging.
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Travier L, Singh R, Sáenz Fernández D, and Deczkowska A
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- Cytokines, Immunologic Factors, Brain, Microglia physiology
- Abstract
Tissue aging can be viewed as a loss of normal maintenance; in advanced age, the mechanisms which keep the tissue healthy on daily bases fail to manage the accumulating "wear and tear", leading to gradual loss of function. In the brain, maintenance is provided primarily by three components: the blood-brain barrier, which allows the influx of certain molecules into the brain while excluding others, the circulation of the cerebrospinal fluid, and the phagocytic function of microglia. Indeed, failure of these systems is associated with cognitive loss and other hallmarks of brain aging. Interestingly, all three mechanisms are regulated not only by internal conditions within the aging brain, but remain highly sensitive to the peripheral signals, such as cytokines or microbiome-derived molecules, present in the systemic circulation. In this article, we discuss the contribution of such peripheral factors to brain maintenance and its loss in aging., Competing Interests: Conflict of interest statement Nothing declared., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)
- Published
- 2022
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4. [Neonatal susceptibility to meningitis results from the immaturity of epithelial barriers and gut microbiota].
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Travier L and Lecuit M
- Subjects
- Humans, Infant, Newborn, Gastrointestinal Microbiome, Meningitis
- Published
- 2022
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5. Isolation and Characterization of the Immune Cells from Micro-dissected Mouse Choroid Plexuses.
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Dominguez-Belloso A, Schmutz S, Novault S, Travier L, and Deczkowska A
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- Aging, Animals, Brain physiology, Choroid, Mice, Blood-Brain Barrier physiology, Choroid Plexus
- Abstract
The brain is no longer considered as an organ functioning in isolation; accumulating evidence suggests that changes in the peripheral immune system can indirectly shape brain function. At the interface between the brain and the systemic circulation, the choroid plexuses (CP), which constitute the blood-cerebrospinal fluid barrier, have been highlighted as a key site of periphery-to-brain communication. CP produce the cerebrospinal fluid, neurotrophic factors, and signaling molecules that can shape brain homeostasis. CP are also an active immunological niche. In contrast to the brain parenchyma, which is populated mainly by microglia under physiological conditions, the heterogeneity of CP immune cells recapitulates the diversity found in other peripheral organs. The CP immune cell diversity and activity change with aging, stress, and disease and modulate the activity of the CP epithelium, thereby indirectly shaping brain function. The goal of this protocol is to isolate murine CP and identify about 90% of the main immune subsets that populate them. This method is a tool to characterize CP immune cells and understand their function in orchestrating periphery-to-brain communication. The proposed protocol may help decipher how CP immune cells indirectly modulate brain function in health and across various disease conditions.
- Published
- 2022
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6. Neonatal susceptibility to meningitis results from the immaturity of epithelial barriers and gut microbiota.
- Author
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Travier L, Alonso M, Andronico A, Hafner L, Disson O, Lledo PM, Cauchemez S, and Lecuit M
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- Aging pathology, Animals, Animals, Newborn, Bacteremia complications, Bacteremia microbiology, Choroid Plexus pathology, Disease Susceptibility, Epithelial Cells metabolism, Host-Pathogen Interactions, Intercellular Junctions metabolism, Intestinal Mucosa blood supply, Mice, Inbred C57BL, Streptococcus agalactiae physiology, Wnt Signaling Pathway, Mice, Gastrointestinal Microbiome, Intestinal Mucosa microbiology, Intestinal Mucosa pathology, Meningitis, Bacterial microbiology, Meningitis, Bacterial pathology
- Abstract
Neonates are highly susceptible to bacterial meningitis as compared to children and adults. Group B streptococcus (GBS) is a major cause of neonatal meningitis. Neonatal meningitis can result from GBS intestinal colonization and translocation across the intestinal barrier (IB). Here, we show that the immaturity of the neonatal intestinal microbiota leads to low resistance to GBS intestinal colonization and permissiveness of the gut-vascular barrier. Moreover, the age-dependent but microbiota-independent Wnt activity in intestinal and choroid plexus (CP) epithelia results in a lower degree of cell-cell junctions' polarization, which favors bacterial translocation. This study thus reveals that neonatal susceptibility to GBS meningitis results from the age-dependent immaturity of the intestinal microbiota and developmental pathways associated with neonatal tissue growth, which both concur to GBS gut colonization, systemic dissemination, and neuroinvasion. Whereas the activation of developmental pathways is intrinsic to neonates, interventions aimed at maturing the microbiota may help prevent neonatal meningitis., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2021
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7. Insights into the structure and assembly of a bacterial cellulose secretion system.
- Author
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Krasteva PV, Bernal-Bayard J, Travier L, Martin FA, Kaminski PA, Karimova G, Fronzes R, and Ghigo JM
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- Adaptation, Physiological physiology, Bacterial Secretion Systems chemistry, Biofilms, Cyclic GMP metabolism, DNA Mutational Analysis, Escherichia coli Proteins chemistry, Escherichia coli Proteins isolation & purification, Escherichia coli Proteins ultrastructure, Membrane Proteins chemistry, Membrane Proteins isolation & purification, Membrane Proteins ultrastructure, Microscopy, Electron, Models, Biological, Protein Binding, Protein Domains physiology, Protein Interaction Maps physiology, Recombinant Proteins chemistry, Recombinant Proteins isolation & purification, Recombinant Proteins metabolism, Recombinant Proteins ultrastructure, Software, Structure-Activity Relationship, Bacterial Secretion Systems metabolism, Cellulose metabolism, Escherichia coli physiology, Escherichia coli Proteins metabolism, Membrane Proteins metabolism
- Abstract
Secreted exopolysaccharides present important determinants for bacterial biofilm formation, survival, and virulence. Cellulose secretion typically requires the concerted action of a c-di-GMP-responsive inner membrane synthase (BcsA), an accessory membrane-anchored protein (BcsB), and several additional Bcs components. Although the BcsAB catalytic duo has been studied in great detail, its interplay with co-expressed subunits remains enigmatic. Here we show that E. coli Bcs proteins partake in a complex protein interaction network. Electron microscopy reveals a stable, megadalton-sized macromolecular assembly, which encompasses most of the inner membrane and cytosolic Bcs components and features a previously unobserved asymmetric architecture. Heterologous reconstitution and mutational analyses point toward a structure-function model, where accessory proteins regulate secretion by affecting both the assembly and stability of the system. Altogether, these results lay the foundation for more comprehensive models of synthase-dependent exopolysaccharide secretion in biofilms and add a sophisticated secretory nanomachine to the diverse bacterial arsenal for virulence and adaptation.
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- 2017
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8. Toxoplasma gondii: biochemical and biophysical characterization of recombinant soluble dense granule proteins GRA2 and GRA6.
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Bittame A, Effantin G, Pètre G, Ruffiot P, Travier L, Schoehn G, Weissenhorn W, Cesbron-Delauw MF, Gagnon J, and Mercier C
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- Antigens, Protozoan genetics, Circular Dichroism, Light, Microscopy, Electron, Transmission, Protein Folding, Protein Structure, Secondary, Protozoan Proteins genetics, Recombinant Proteins chemistry, Recombinant Proteins genetics, Scattering, Radiation, Solubility, Antigens, Protozoan chemistry, Protozoan Proteins chemistry
- Abstract
The most prominent structural feature of the parasitophorous vacuole (PV) in which the intracellular parasite Toxoplasma gondii proliferates is a membranous nanotubular network (MNN), which interconnects the parasites and the PV membrane. The MNN function remains unclear. The GRA2 and GRA6 proteins secreted from the parasite dense granules into the PV have been implicated in the MNN biogenesis. Amphipathic alpha-helices (AAHs) predicted in GRA2 and an alpha-helical hydrophobic domain predicted in GRA6 have been proposed to be responsible for their membrane association, thereby potentially molding the MMN in its structure. Here we report an analysis of the recombinant proteins (expressed in detergent-free conditions) by circular dichroism, which showed that full length GRA2 displays an alpha-helical secondary structure while recombinant GRA6 and GRA2 truncated of its AAHs are mainly random coiled. Dynamic light scattering and transmission electron microscopy showed that recombinant GRA6 and truncated GRA2 constitute a homogenous population of small particles (6-8 nm in diameter) while recombinant GRA2 corresponds to 2 populations of particles (∼8-15 nm and up to 40 nm in diameter, respectively). The unusual properties of GRA2 due to its AAHs are discussed., (Copyright © 2015 Elsevier Inc. All rights reserved.)
- Published
- 2015
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9. PI3-kinase activation is critical for host barrier permissiveness to Listeria monocytogenes.
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Gessain G, Tsai YH, Travier L, Bonazzi M, Grayo S, Cossart P, Charlier C, Disson O, and Lecuit M
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- Animals, Bacterial Proteins metabolism, Cadherins metabolism, Cell Line, Chorionic Villi immunology, Chorionic Villi metabolism, Chorionic Villi microbiology, Enzyme Activation, Female, Goblet Cells metabolism, Humans, Intestinal Mucosa immunology, Intestinal Mucosa metabolism, Intestinal Mucosa microbiology, Intestines immunology, Intestines microbiology, Mice, Mice, Transgenic, Peyer's Patches immunology, Peyer's Patches metabolism, Phosphorylation, Placenta immunology, Placenta metabolism, Placenta microbiology, Pregnancy, Protein Binding, Proto-Oncogene Proteins c-akt metabolism, Signal Transduction, Trophoblasts metabolism, Host-Pathogen Interactions, Listeria monocytogenes immunology, Listeriosis immunology, Listeriosis metabolism, Phosphatidylinositol 3-Kinases metabolism
- Abstract
Invasion of nonphagocytic cells, a critical property of Listeria monocytogenes (Lm) that enables it to cross host barriers, is mediated by the interaction of two bacterial surface proteins, InlA and InlB, with their respective receptors E-cadherin and c-Met. Although InlA-E-cadherin interaction is necessary and sufficient for Lm crossing of the intestinal barrier, both InlA and InlB are required for Lm crossing of the placental barrier. The mechanisms underlying these differences are unknown. Phosphoinositide 3-kinase (PI3-K) is involved in both InlA- and InlB-dependent pathways. Indeed, InlA-dependent entry requires PI3-K activity but does not activate it, whereas InlB-c-Met interaction activates PI3-K. We show that Lm intestinal target cells exhibit a constitutive PI3-K activity, rendering InlB dispensable for InlA-dependent Lm intestinal barrier crossing. In contrast, the placental barrier does not exhibit constitutive PI3-K activity, making InlB necessary for InlA-dependent Lm placental invasion. Here, we provide the molecular explanation for the respective contributions of InlA and InlB to Lm host barrier invasion, and reveal the critical role of InlB in rendering cells permissive to InlA-mediated invasion. This study shows that PI3-K activity is critical to host barrier permissiveness to microbes, and that pathogens exploit both similarities and differences of host barriers to disseminate., (© 2015 Gessain et al.)
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- 2015
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10. Listeria monocytogenes-associated biliary tract infections: a study of 12 consecutive cases and review.
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Charlier C, Fevre C, Travier L, Cazenave B, Bracq-Dieye H, Podevin J, Assomany D, Guilbert L, Bossard C, Carpentier F, Cales V, Leclercq A, and Lecuit M
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- Abdominal Pain epidemiology, Abdominal Pain microbiology, Adult, Aged, Aged, 80 and over, Anti-Bacterial Agents therapeutic use, Bacteremia diagnosis, Bacteremia drug therapy, Bacteremia epidemiology, Biliary Tract Diseases drug therapy, Biliary Tract Diseases epidemiology, Cholangitis drug therapy, Cholangitis epidemiology, Cholecystectomy statistics & numerical data, Cholecystitis drug therapy, Cholecystitis epidemiology, Cholecystolithiasis epidemiology, Comorbidity, Cysts drug therapy, Cysts epidemiology, Drug Resistance, Bacterial, Female, Fever epidemiology, Fever microbiology, France epidemiology, Gallbladder Diseases epidemiology, Gallbladder Diseases microbiology, Humans, Immunosuppressive Agents adverse effects, Listeria monocytogenes genetics, Listeriosis drug therapy, Male, Medication Errors, Middle Aged, Necrosis, Penicillins therapeutic use, Population Surveillance, Retrospective Studies, Biliary Tract Diseases microbiology, Cholangitis microbiology, Cholecystitis microbiology, Cysts microbiology, Listeriosis epidemiology
- Abstract
At present, little is known regarding Listeria monocytogenes-associated biliary tract infection, a rare form of listeriosis.In this article, we will study 12 culture-proven cases reported to the French National Reference Center for Listeria from 1996 to 2013 and review the 8 previously published cases.Twenty cases were studied: 17 cholecystitis, 2 cholangitis, and 1 biliary cyst infection. Half were men with a median age of 69 years (32-85). Comorbidities were present in 80%, including cirrhosis, rheumatoid arthritis, and diabetes. Five patients received immunosuppressive therapy, including corticosteroids and anti-tumor necrosis factor biotherapies. Half were afebrile. Blood cultures were positive in 60% (3/5). Gallbladder histological lesions were analyzed in 3 patients and evidenced acute, chronic, or necrotic exacerbation of chronic infection. Genoserogroup of the 12 available strains were IVb (n=6), IIb (n=5), and IIa (n=1). Their survival in the bile was not enhanced when compared with isolates from other listeriosis cases. Adverse outcome was reported in 33% (5/15): 3 deaths, 1 recurrence; 75% of the patients with adverse outcome received inadequate antimicrobial therapy (P=0.033).Biliary tract listeriosis is a severe infection associated with high mortality in patients not treated with appropriate therapy. This study provides medical relevance to in vitro and animal studies that had shown Listeria monocytogenes ability to survive in bile and induce overt biliary infections.
- Published
- 2014
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11. Escherichia coli resistance to nonbiocidal antibiofilm polysaccharides is rare and mediated by multiple mutations leading to surface physicochemical modifications.
- Author
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Travier L, Rendueles O, Ferrières L, Herry JM, and Ghigo JM
- Subjects
- Anti-Bacterial Agents pharmacology, Bacterial Adhesion drug effects, Chemical Phenomena, DNA Transposable Elements, Drug Resistance, Multiple, Bacterial, Escherichia coli chemistry, Escherichia coli genetics, Lewis Bases chemistry, Microbial Sensitivity Tests, Polymyxin B pharmacology, Polysorbates pharmacology, Biofilms drug effects, Escherichia coli drug effects, Genes, Bacterial, Mutation, Polysaccharides pharmacology
- Abstract
Antivirulence strategies targeting bacterial behavior, such as adhesion and biofilm formation, are expected to exert low selective pressure and have been proposed as alternatives to biocidal antibiotic treatments to avoid the rapid occurrence of bacterial resistance. Here, we tested this hypothesis using group 2 capsule polysaccharide (G2cps), a polysaccharidic molecule previously shown to impair bacterium-surface interactions, and we investigated the nature of bacterial resistance to a nonbiocidal antibiofilm strategy. We screened an Escherichia coli mutant library for an increased ability to form biofilm in the presence of G2cps, and we identified several mutants displaying partial but not total resistance to this antibiofilm polysaccharide. Our genetic analysis showed that partial resistance to G2cps results from multiple unrelated mutations leading to modifications in surface physicochemical properties that counteract the changes in ionic charge and Lewis base properties induced by G2cps. Moreover, some of the identified mutants harboring improved biofilm formation in the presence of G2cps were also partially resistant to other antibiofilm molecules. This study therefore shows that alterations of bacterial surface properties mediate only partial resistance to G2cps. It also experimentally validates the potential value of nonbiocidal antibiofilm strategies, since full resistance to antibiofilm compounds is rare and potentially unlikely to arise in clinical settings.
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- 2013
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12. ActA promotes Listeria monocytogenes aggregation, intestinal colonization and carriage.
- Author
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Travier L, Guadagnini S, Gouin E, Dufour A, Chenal-Francisque V, Cossart P, Olivo-Marin JC, Ghigo JM, Disson O, and Lecuit M
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- Animals, Cecum microbiology, Cell Line, Colon microbiology, Disease Models, Animal, Feces microbiology, Host-Pathogen Interactions, Humans, Intestinal Mucosa microbiology, Listeria monocytogenes growth & development, Listeria monocytogenes metabolism, Listeriosis metabolism, Listeriosis microbiology, Mice, Virulence Factors metabolism, Bacterial Proteins metabolism, Biofilms growth & development, Cecum metabolism, Colon metabolism, Intestinal Mucosa metabolism, Listeria monocytogenes pathogenicity, Membrane Proteins metabolism
- Abstract
Listeria monocytogenes (Lm) is a ubiquitous bacterium able to survive and thrive within the environment and readily colonizes a wide range of substrates, often as a biofilm. It is also a facultative intracellular pathogen, which actively invades diverse hosts and induces listeriosis. So far, these two complementary facets of Lm biology have been studied independently. Here we demonstrate that the major Lm virulence determinant ActA, a PrfA-regulated gene product enabling actin polymerization and thereby promoting its intracellular motility and cell-to-cell spread, is critical for bacterial aggregation and biofilm formation. We show that ActA mediates Lm aggregation via direct ActA-ActA interactions and that the ActA C-terminal region, which is not involved in actin polymerization, is essential for aggregation in vitro. In mice permissive to orally-acquired listeriosis, ActA-mediated Lm aggregation is not observed in infected tissues but occurs in the gut lumen. Strikingly, ActA-dependent aggregating bacteria exhibit an increased ability to persist within the cecum and colon lumen of mice, and are shed in the feces three order of magnitude more efficiently and for twice as long than bacteria unable to aggregate. In conclusion, this study identifies a novel function for ActA and illustrates that in addition to contributing to its dissemination within the host, ActA plays a key role in Lm persistence within the host and in transmission from the host back to the environment.
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- 2013
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13. Listeria monocytogenes-associated joint and bone infections: a study of 43 consecutive cases.
- Author
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Charlier C, Leclercq A, Cazenave B, Desplaces N, Travier L, Cantinelli T, Lortholary O, Goulet V, Le Monnier A, and Lecuit M
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- Adolescent, Adult, Aged, Aged, 80 and over, Biofilms, Electrophoresis, Gel, Pulsed-Field, Female, France, Humans, Listeria monocytogenes classification, Listeria monocytogenes genetics, Listeria monocytogenes physiology, Listeriosis drug therapy, Male, Middle Aged, Osteomyelitis drug therapy, Prosthesis-Related Infections drug therapy, Retrospective Studies, Listeria monocytogenes isolation & purification, Listeriosis microbiology, Osteomyelitis microbiology, Prosthesis-Related Infections microbiology
- Abstract
Background: Little is known about Listeria monocytogenes-associated bone and joint infections. Only case reports of this infection have been published., Methods: Retrospective study of culture-proven bone and joint cases reported to the French National Reference Center for Listeria from 1992 to 2010., Results: Forty-three patients were studied: 61% were men, and the median age was 72 (range, 16-89); 24 patients exhibited comorbidities (56%). Thirty-six patients (84%) had orthopedic implant devices: prosthetic joints (n = 34) or internal fixation (n = 2); the median time after insertion was 9 years (0.1-22). Subacute infection was more frequent (median, 4 weeks [range, 2-100], 74%) than acute infection (<7 days, 23%), with nonspecific clinical features; 45% of patients had no fever. Blood cultures were positive in 3 of 19 cases. Isolate polymerase chain reaction genogrouping revealed 4 patterns: IVb (21 of 42, 50%), IIa (17 of 42, 40%), IIb (2 of 42, 5%), and IIc (2 of 42, 5%). Five groups of strains with similar pulsotype patterns were identified without an epidemiological link. Antibiotics, primarily amoxicillin (80%) with aminoglycosides (48%), were prescribed for a median duration of 15 weeks (range, 2-88). Eighteen patients (50%) underwent prosthesis replacement; all were successful after median follow-up of 10 months (range, 1-75). Five of 13 patients for whom material was not removed had protracted infection despite prolonged antibiotherapy; 3 of these patients later underwent prosthesis replacement with sustained recovery., Conclusions: Osteoarticular listeriosis primarily involves prosthetic joints and occurs in immunocompromised patients. It requires intensive treatment with antibiotherapy and usually requires implant removal or replacement for cure.
- Published
- 2012
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14. Activation of type III interferon genes by pathogenic bacteria in infected epithelial cells and mouse placenta.
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Bierne H, Travier L, Mahlakõiv T, Tailleux L, Subtil A, Lebreton A, Paliwal A, Gicquel B, Staeheli P, Lecuit M, and Cossart P
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- Animals, Female, Mice, Pregnancy, Real-Time Polymerase Chain Reaction, Reverse Transcriptase Polymerase Chain Reaction, Bacteria pathogenicity, Epithelial Cells microbiology, Interferons genetics, Placenta microbiology
- Abstract
Bacterial infections trigger the expression of type I and II interferon genes but little is known about their effect on type III interferon (IFN-λ) genes, whose products play important roles in epithelial innate immunity against viruses. Here, we studied the expression of IFN-λ genes in cultured human epithelial cells infected with different pathogenic bacteria and in the mouse placenta infected with Listeria monocytogenes. We first showed that in intestinal LoVo cells, induction of IFN-λ genes by L. monocytogenes required bacterial entry and increased further during the bacterial intracellular phase of infection. Other Gram-positive bacteria, Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis, also induced IFN-λ genes when internalized by LoVo cells. In contrast, Gram-negative bacteria Salmonella enterica serovar Typhimurium, Shigella flexneri and Chlamydia trachomatis did not substantially induce IFN-λ. We also found that IFN-λ genes were up-regulated in A549 lung epithelial cells infected with Mycobacterium tuberculosis and in HepG2 hepatocytes and BeWo trophoblastic cells infected with L. monocytogenes. In a humanized mouse line permissive to fetoplacental listeriosis, IFN-λ2/λ3 mRNA levels were enhanced in placentas infected with L. monocytogenes. In addition, the feto-placental tissue was responsive to IFN-λ2. Together, these results suggest that IFN-λ may be an important modulator of the immune response to Gram-positive intracellular bacteria in epithelial tissues.
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- 2012
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15. Screening of Escherichia coli species biodiversity reveals new biofilm-associated antiadhesion polysaccharides.
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Rendueles O, Travier L, Latour-Lambert P, Fontaine T, Magnus J, Denamur E, and Ghigo JM
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- Anti-Bacterial Agents isolation & purification, Anti-Bacterial Agents metabolism, Humans, Staphylococcus aureus growth & development, Bacterial Adhesion drug effects, Biofilms growth & development, Escherichia coli physiology, Polysaccharides, Bacterial isolation & purification, Polysaccharides, Bacterial metabolism, Staphylococcus aureus drug effects
- Abstract
Unlabelled: Bacterial biofilms often form multispecies communities in which complex but ill-understood competition and cooperation interactions occur. In light of the profound physiological modifications associated with this lifestyle, we hypothesized that the biofilm environment might represent an untapped source of natural bioactive molecules interfering with bacterial adhesion or biofilm formation. We produced cell-free solutions extracted from in vitro mature biofilms formed by 122 natural Escherichia coli isolates, and we screened these biofilm extracts for antiadhesion molecules active on a panel of Gram-positive and Gram-negative bacteria. Using this approach, we showed that 20% of the tested biofilm extracts contained molecules that antagonize bacterial growth or adhesion. We characterized a compound, produced by a commensal animal E. coli strain, for which activity is detected only in biofilm extract. Biochemical and genetic analyses showed that this compound corresponds to a new type of released high-molecular-weight polysaccharide whose biofilm-associated production is regulated by the RfaH protein. We demonstrated that the antiadhesion activity of this polysaccharide was restricted to Gram-positive bacteria and that its production reduced susceptibility to invasion and provided rapid exclusion of Staphylococcus aureus from mixed E. coli and S. aureus biofilms. Our results therefore demonstrate that biofilms contain molecules that contribute to the dynamics of mixed bacterial communities and that are not or only poorly detected in unconcentrated planktonic supernatants. Systematic identification of these compounds could lead to strategies that limit pathogen surface colonization and reduce the burden associated with the development of bacterial biofilms on medical devices., Importance: We sought to demonstrate that bacterial biofilms are reservoirs for unknown molecules that antagonize bacterial adhesion. The use of natural strains representative of Escherichia coli species biodiversity showed that nonbiocidal antiadhesion polysaccharides are frequently found in mature biofilm extracts (bacterium-free suspensions which contain soluble molecules produced within the biofilm). Release of an antiadhesion polysaccharide confers a competitive advantage upon the producing strain against clinically relevant pathogens such as Staphylococcus aureus. Hence, exploring the biofilm environment provides a better understanding of bacterial interactions within complex communities and could lead to improved control of pathogen colonization.
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- 2011
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16. GRA12, a Toxoplasma dense granule protein associated with the intravacuolar membranous nanotubular network.
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Michelin A, Bittame A, Bordat Y, Travier L, Mercier C, Dubremetz JF, and Lebrun M
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- Animals, Antigens, Protozoan metabolism, Cell Line, DNA, Protozoan analysis, DNA, Protozoan genetics, Fluorescent Antibody Technique, Host-Parasite Interactions, Humans, Intracellular Membranes parasitology, Membrane Proteins genetics, Membrane Proteins metabolism, Microscopy, Immunoelectron, Molecular Sequence Data, Protein Transport, Protozoan Proteins genetics, Sequence Analysis, Protein, Toxoplasma ultrastructure, Toxoplasmosis metabolism, Vacuoles parasitology, Intracellular Membranes metabolism, Microtubules metabolism, Protozoan Proteins metabolism, Toxoplasma physiology, Toxoplasmosis parasitology, Vacuoles metabolism
- Abstract
The intracellular protozoan parasite Toxoplasma gondii develops within the parasitophorous vacuole (PV), an intracellular niche in which it secretes proteins from secretory organelles named dense granules and rhoptries. Here, we describe a new dense granule protein that should now be referred to as GRA12, and that displays no homology with other proteins. Immunofluorescence and immuno-electron microscopy showed that GRA12 behaves similarly to both GRA2 and GRA6. It is secreted into the PV from the anterior pole of the parasite soon after the beginning of invasion, transits to the posterior invaginated pocket of the parasite where a membranous tubulovesicular network is first assembled, and finally resides throughout the vacuolar space, associated with the mature membranous nanotubular network. GRA12 fails to localise at the parasite posterior end in the absence of GRA2. Within the vacuolar space, like the other GRA proteins, GRA12 exists in both a soluble and a membrane-associated form. Using affinity chromatography experiments, we showed that in both the parasite and the PV soluble fractions, GRA12 is purified with the complex of GRA proteins associated with a tagged version of GRA2 and that this association is lost in the PV membranous fraction.
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- 2009
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17. Functional domains of the Toxoplasma GRA2 protein in the formation of the membranous nanotubular network of the parasitophorous vacuole.
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Travier L, Mondragon R, Dubremetz JF, Musset K, Mondragon M, Gonzalez S, Cesbron-Delauw MF, and Mercier C
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- Amino Acid Motifs genetics, Animals, Animals, Genetically Modified, Antigens, Protozoan genetics, Fluorescent Antibody Technique, Indirect, Gene Deletion, Host-Parasite Interactions, Hydrophobic and Hydrophilic Interactions, Immunoblotting, Microscopy, Electron, Mutagenesis, Site-Directed methods, Protozoan Proteins genetics, Toxoplasma genetics, Toxoplasma ultrastructure, Vacuoles ultrastructure, Antigens, Protozoan chemistry, Protozoan Proteins chemistry, Toxoplasma chemistry, Vacuoles chemistry
- Abstract
Amphipathic alpha-helices have been proposed as the general means used by soluble proteins to induce membrane tubulation. Previous studies had shown that the GRA2 dense granule protein of Toxoplasma gondii would be a crucial protein for the formation of the intravacuolar membranous nanotubular network (MNN) and that one of the functions of the MNN is to organise the parasites within the parasitophorous vacuole. GRA2 is a small protein (185 amino acids), predicted to contain three amphipathic alpha-helices (alpha1: 70-92; alpha2: 95-110 and alpha3: 119-139) when using the standard programs of secondary structure prediction. To investigate the respective contribution of each alpha-helix in the GRA2 functions, we used DeltaGRA2-HXGPRT knock-out complementation: eight truncated forms of GRA2 were expressed in the deleted recipient and the phenotypes of these mutants were analysed. This study showed that: (i) alpha3, when associated with the N-terminal region (NT) and the C-terminal region (CT), is sufficient to target the protein to the parasite posterior end and to induce formation of membranous vesicles within the vacuole. However, when associated only with CT, alpha3 is not sufficient to provide the hydrophobicity required for membrane association; (ii) the alpha1alpha2 region is alone not sufficient to induce membrane tubulation within the PV; and (iii) only one mutant, NT-alpha1alpha2alpha3, restores most of the biochemical and functional properties of GRA2, including traffic to the dense granules, secretion into the vacuole, association with vacuolar membranes, induction of the MNN formation and organisation of the parasites within the vacuole.
- Published
- 2008
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18. Apicomplexa in mammalian cells: trafficking to the parasitophorous vacuole.
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Cesbron-Delauw MF, Gendrin C, Travier L, Ruffiot P, and Mercier C
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- Animals, Apicomplexa cytology, Cell Membrane metabolism, Host-Parasite Interactions, Plasmodium falciparum metabolism, Plasmodium falciparum pathogenicity, Toxoplasma metabolism, Toxoplasma pathogenicity, Apicomplexa metabolism, Apicomplexa pathogenicity, Vacuoles metabolism
- Abstract
Most Apicomplexa reside and multiply in the cytoplasm of their host cell, within a parasitophorous vacuole (PV) originating from both parasite and host cell components. Trafficking of parasite-encoded proteins destined to membrane compartments beyond the confine of the parasite plasma membrane is a process that offers a rich territory to explore novel mechanisms of protein-membrane interactions. Here, we focus on the PVs formed by the asexual stages of two pathogens of medical importance, Plasmodium and Toxoplasma. We compare the PVs of both parasites, with a particular emphasis on their evolutionary divergent compartmentalization within the host cell. We also discuss the existence of peculiar export mechanisms and/or sorting determinants that are potentially involved in the post-secretory targeting of parasite proteins to the PV subcompartments.
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- 2008
- Full Text
- View/download PDF
19. Purification of Toxoplasma dense granule proteins reveals that they are in complexes throughout the secretory pathway.
- Author
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Braun L, Travier L, Kieffer S, Musset K, Garin J, Mercier C, and Cesbron-Delauw MF
- Subjects
- Animals, Cell Fractionation, Chromatography, Affinity, Fluorescent Antibody Technique, Indirect, Immunoblotting, Intracellular Membranes chemistry, Protein Binding, Vacuoles chemistry, Vacuoles parasitology, Macromolecular Substances isolation & purification, Macromolecular Substances metabolism, Protozoan Proteins isolation & purification, Protozoan Proteins metabolism, Toxoplasma chemistry
- Abstract
Dense granules are Apicomplexa specific secretory organelles. In Toxoplasma gondii, the dense granules proteins, named GRA proteins, are massively secreted into the parasitophorous vacuole (PV) shortly after invasion. Despite the presence of hydrophobic membrane segments, they are stored as both soluble and aggregated forms within the dense granules and are secreted as soluble forms into the vacuolar space where they further stably associate with PV membranes. In this study, we explored the unusual biochemical behavior of GRA proteins during their trafficking. Conventional chromatography indicated that the GRA proteins form high globular weight complexes within the parasite. To confirm these results, DeltaGRA knocked-out parasites were stably complemented with their respective HA-FLAG tagged GRA2 or GRA5. Purification of the tagged proteins by affinity chromatography showed that within the parasite and the PV soluble fraction, both the soluble GRA2-HA-FLAG and GRA5-HA-FLAG associate with several GRA proteins, the major ones being GRA3, GRA6 and GRA7. Following their insertion into the PV membranes, GRA2-HA-FLAG associated with GRA5 and GRA7 while GRA5-HA-FLAG associated with GRA7 only. Taken together, these data suggest that the GRA proteins form oligomeric complexes that may explain their solubility within the dense granules and the vacuolar matrix by sequestering their hydrophobic domains within the interior of the complex. Insertion into the PV membranes correlates with the decrease of the GRA partners number.
- Published
- 2008
- Full Text
- View/download PDF
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