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Relationship between biofilm formation and antibiotic resistance in commensal isolates of Staphylococcus epidermidis

Oliveira, Fernando; Melo, Luís D. R.; Cerca, Nuno
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
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Staphylococcus epidermidis is a common bacterial coloniser of the normal human microflora and usually have a benign relationship with the host. For several years, S. epidermidis was regarded as a harmless commensal microorganism. However, this bacterium is now recognised as an opportunistic pathogen, representing a leading cause of healthcare-associated infections. The major recognised determinants in the pathogenesis of S. epidermidis infections are its ability to form thick and multilayered biofilms along with high resistance to several classes of antibiotics. Biofilms are defined as structured communities of microorganisms embedded in a self-produced matrix of extracellular polymeric. It is well established that bacteria exhibiting a biofilm phenotype are more recalcitrant to antibiotic therapy. Hence, these two pathogenic features stated above appear to be intimately related. The present study aimed to evaluate the pathogenic potential of commensal S. epidermidis isolates through the assessment of their biofilm formation ability and antibiotic susceptibility profiles, as well as to analyse the relationship between biofilm formation and antibiotic resistance. To achieve that, thirty-one S. epidermidis isolates from Portuguese healthy volunteers (obtained from September 2012 to April 2013) were tested for biofilm formation ability...

Genetic similarity and phenotypic diversity of commensal and pathogenic strains of Candida albicans isolated from the oral cavity.

Hellstein, J; Vawter-Hugart, H; Fotos, P; Schmid, J; Soll, D R
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1993 EN
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Colony phenotype and genetic similarity were assessed within and between groups of commensal and pathogenic strains of Candida albicans collected from the oral cavities of individuals in a single geographical locale. Thirty-eight percent of pathogenic isolates contained predominant or minor variant colony morphologies (other than smooth) when samples from the sites of infection were cultured on plates, while 16% of commensal isolates contained minor variant colony morphologies when samples from the sites of carriage were cultured. The genetic similarities of isolates within and between groups were assessed by DNA fingerprinting by using Southern blot hybridization with the fingerprinting probe Ca3 and analysis with the computer-assisted, automated Dendron system. Both the commensal and the pathogenic groups contained a major cluster of genetically similar C. albicans isolates representing 31 and 33% of the strains in the respective groups. When a combined dendrogram of both commensal and pathogenic isolates was generated, the major clusters of genetically similar isolates in each group mixed into one large cluster. Minor clusters in the individual dendrograms also mixed. These results suggest common clonal origins for commensal and pathogenic strains in the same geographical locale.

Measurements of Fitness and Competition in Commensal Escherichia coli and E. coli O157:H7 Strains†

Durso, Lisa M.; Smith, David; Hutkins, Robert W.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/2004 EN
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Although the main reservoirs for pathogenic Escherichia coli O157:H7 are cattle and the cattle environment, factors that affect its tenure in the bovine host and its survival outside humans and cattle have not been well studied. It is also not understood what physiological properties, if any, distinguish these pathogens from commensal counterparts that live as normal members of the human and bovine gastrointestinal tracts. To address these questions, individual and competitive fitness experiments, indirect antagonism assays, and antibiotic resistance and carbon utilization analyses were conducted using a strain set consisting of 122 commensal and pathogenic strains. The individual fitness experiments, under four different environments (rich medium, aerobic and anaerobic; rumen medium, anaerobic; and a minimal medium, aerobic) revealed no differences in growth rates between commensal E. coli and E. coli O157:H7 strains. Indirect antagonism assays revealed that E. coli O157:H7 strains more frequently produced inhibitory substances than commensal strains did, under the conditions tested, although both groups displayed moderate sensitivity. Only minor differences were noted in the antibiotic resistance patterns of the two groups. In contrast...

Detection of Virulence-Associated Genes Not Useful for Discriminating between Invasive and Commensal Staphylococcus epidermidis Strains from a Bone Marrow Transplant Unit

Rohde, Holger; Kalitzky, Matthias; Kröger, Nicolaus; Scherpe, Stefanie; Horstkotte, Matthias A.; Knobloch, Johannes K.-M.; Zander, Axel R.; Mack, Dietrich
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2004 EN
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Because of their biofilm-forming capacity, invasive Staphylococcus epidermidis isolates, which cause the majority of nosocomial catheter-related bloodstream infections (BSIs), are thought to be selected at the time of catheter insertion from a population of less virulent commensal strains. This fact allows the prediction that invasive and contaminating strains can be differentiated via detection of virulence-associated genes. However, the hospital environment may pave the way for catheter-related infections by promoting a shift in the commensal bacterial population toward strains with enhanced virulence. The distribution of virulence-associated genes (icaADBC, aap, atlE, bhp, fbe, embp, mecA, IS256, and IS257), polysaccharide intercellular adhesin synthesis, and biofilm formation were investigated in S. epidermidis strains from independent episodes of catheter-related BSIs in individuals who have received bone marrow transplantation (BMT). The results were compared with those obtained for commensal S. epidermidis isolates from hospitalized patients after BMT and from healthy individuals, respectively. The clonal relationships of the strains were investigated by pulsed-field gel electrophoresis. icaADBC, mecA, and IS256 were significantly more prevalent in BSI isolates than in commensal isolates from healthy individuals. However...

Commensal-dependent expression of IL-25 regulates the IL-23–IL-17 axis in the intestine

Zaph, Colby; Du, Yurong; Saenz, Steven A.; Nair, Meera G.; Perrigoue, Jacqueline G.; Taylor, Betsy C.; Troy, Amy E.; Kobuley, Dmytro E.; Kastelein, Robert A.; Cua, Daniel J.; Yu, Yimin; Artis, David
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 29/09/2008 EN
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Alterations in the composition of intestinal commensal bacteria are associated with enhanced susceptibility to multiple inflammatory diseases, including those conditions associated with interleukin (IL)-17–producing CD4+ T helper (Th17) cells. However, the relationship between commensal bacteria and the expression of proinflammatory cytokines remains unclear. Using germ-free mice, we show that the frequency of Th17 cells in the large intestine is significantly elevated in the absence of commensal bacteria. Commensal-dependent expression of the IL-17 family member IL-25 (IL-17E) by intestinal epithelial cells limits the expansion of Th17 cells in the intestine by inhibiting expression of macrophage-derived IL-23. We propose that acquisition of, or alterations in, commensal bacteria influences intestinal immune homeostasis via direct regulation of the IL-25–IL-23–IL-17 axis.

Precolonized Human Commensal Escherichia coli Strains Serve as a Barrier to E. coli O157:H7 Growth in the Streptomycin-Treated Mouse Intestine▿

Leatham, Mary P.; Banerjee, Swati; Autieri, Steven M.; Mercado-Lubo, Regino; Conway, Tyrrell; Cohen, Paul S.
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
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Different Escherichia coli strains generally have the same metabolic capacity for growth on sugars in vitro, but they appear to use different sugars in the streptomycin-treated mouse intestine (Fabich et al., Infect. Immun. 76:1143-1152, 2008). Here, mice were precolonized with any of three human commensal strains (E. coli MG1655, E. coli HS, or E. coli Nissle 1917) and 10 days later were fed 105 CFU of the same strains. While each precolonized strain nearly eliminated its isogenic strain, confirming that colonization resistance can be modeled in mice, each allowed growth of the other commensal strains to higher numbers, consistent with different commensal E. coli strains using different nutrients in the intestine. Mice were also precolonized with any of five commensal E. coli strains for 10 days and then were fed 105 CFU of E. coli EDL933, an O157:H7 pathogen. E. coli Nissle 1917 and E. coli EFC1 limited growth of E. coli EDL933 in the intestine (103 to 104 CFU/gram of feces), whereas E. coli MG1655, E. coli HS, and E. coli EFC2 allowed growth to higher numbers (106 to 107 CFU/gram of feces). Importantly, when E. coli EDL933 was fed to mice previously co-colonized with three E. coli strains (MG1655, HS, and Nissle 1917), it was eliminated from the intestine (<10 CFU/gram of feces). These results confirm that commensal E. coli strains can provide a barrier to infection and suggest that it may be possible to construct E. coli probiotic strains that prevent growth of pathogenic E. coli strains in the intestine.

Muc2 Protects against Lethal Infectious Colitis by Disassociating Pathogenic and Commensal Bacteria from the Colonic Mucosa

Bergstrom, Kirk S. B.; Kissoon-Singh, Vanessa; Gibson, Deanna L.; Ma, Caixia; Montero, Marinieve; Sham, Ho Pan; Ryz, Natasha; Huang, Tina; Velcich, Anna; Finlay, B. Brett; Chadee, Kris; Vallance, Bruce A.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN
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Despite recent advances in our understanding of the pathogenesis of attaching and effacing (A/E) Escherichia coli infections, the mechanisms by which the host defends against these microbes are unclear. The goal of this study was to determine the role of goblet cell-derived Muc2, the major intestinal secretory mucin and primary component of the mucus layer, in host protection against A/E pathogens. To assess the role of Muc2 during A/E bacterial infections, we inoculated Muc2 deficient (Muc2−/−) mice with Citrobacter rodentium, a murine A/E pathogen related to diarrheagenic A/E E. coli. Unlike wildtype (WT) mice, infected Muc2−/− mice exhibited rapid weight loss and suffered up to 90% mortality. Stool plating demonstrated 10–100 fold greater C. rodentium burdens in Muc2−/− vs. WT mice, most of which were found to be loosely adherent to the colonic mucosa. Histology of Muc2−/− mice revealed ulceration in the colon amid focal bacterial microcolonies. Metabolic labeling of secreted mucins in the large intestine demonstrated that mucin secretion was markedly increased in WT mice during infection compared to uninfected controls, suggesting that the host uses increased mucin release to flush pathogens from the mucosal surface. Muc2 also impacted host-commensal interactions during infection...

Commensal bacteria can enter colonic epithelial cells and induce proinflammatory cytokine secretion: a possible pathogenic mechanism of ulcerative colitis

Ohkusa, Toshifumi; Yoshida, Tsutomu; Sato, Nobuhiro; Watanabe, Sumio; Tajiri, Hisao; Okayasu, Isao
Fonte: Society for General Microbiology Publicador: Society for General Microbiology
Tipo: Artigo de Revista Científica
Publicado em /05/2009 EN
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Interleukin 2 (IL-2)- and IL-10-knockout mice develop spontaneous colitis under conventional but not germ-free conditions, suggesting that commensal bacteria play an important role in the pathogenesis of colitis. However, interactions between commensal bacteria and colonic epithelial cells have not been fully investigated. We therefore assessed the ability of various commensal bacteria and probiotics to adhere to and invade colonic epithelial cells. Effects of the bacteria on production of proinflammatory cytokines were also measured. Commensal bacteria, including mucosal organisms isolated from ulcerative colitis (UC) patients, such as Fusobacterium varium, reported as a possible pathogen in UC, Bacteroides vulgatus, Escherichia coli and Clostridium clostridioforme, as well as their type strains and probiotics, were assessed for their ability to adhere to and invade colonic epithelial cells using two cell lines, SW-480 and HT-29. Our experiments employed co-incubation, a combination of scanning and transmission electron microscopy and recovery of bacteria from infected-cell lysates. F. varium and several other commensal bacteria, but not probiotics, adhered to colonic epithelial cells and invaded their cytoplasm. ELISA and real-time PCR revealed that the host cells...

Commensal-Epithelial Signaling Mediated via Formyl Peptide Receptors

Wentworth, Christy C.; Jones, Rheinallt M.; Kwon, Young Man; Nusrat, Asma; Neish, Andrew S.
Fonte: American Society for Investigative Pathology Publicador: American Society for Investigative Pathology
Tipo: Artigo de Revista Científica
Publicado em /12/2010 EN
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Commensal bacteria and/or their products engender beneficial effects to the mammalian gut, including stimulating physiological cellular turnover and enhancing wound healing, without activating overt inflammation. In the present study, we observed commensal bacteria-mediated activation of the noninflammatory extracellular signal-regulated kinase[ERK]/mitogen-activated protein kinase and Akt signaling pathways in gut epithelial cells and delineated a mechanism for this bacterially activated signaling. All tested strains of commensal bacteria induced ERK phosphorylation without stimulating pro-inflammatory phospho-IκB or pro-apoptotic phospho-c-Jun NH2-terminal kinase, with Lactobacillus species being most potent. This pattern of signaling activation was recapitulated using the peptide N-formyl-Met-Leu-Phe, a bacterial product known to stimulate signaling events in mammalian phagocytes. Sensing of N-formyl-Met-Leu-Phe by gut epithelial cells occurs via recently characterized formyl peptide receptors located in the plasma membrane. Both commensal bacteria and N-formyl-Met-Leu-Phe application to the apical surface of polarized gut epithelial cells resulted in specific formyl peptide receptor activation. In addition, pretreatment of model epithelia and murine colon with Boc2 (a specific peptide antagonist) or pertussis toxin (a Gi-protein inhibitor) abolished commensal-mediated ERK phosphorylation. Taken together...

Enteric Commensal Bacteria Induce Extracellular Signal-regulated Kinase Pathway Signaling via Formyl Peptide Receptor-dependent Redox Modulation of Dual Specific Phosphatase 3*

Wentworth, Christy C.; Alam, Ashfaqul; Jones, Rheinallt M.; Nusrat, Asma; Neish, Andrew S.
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
EN
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The normal microbial occupants of the mammalian intestine are crucial for maintaining gut homeostasis, yet the mechanisms by which intestinal cells perceive and respond to the microbiota are largely unknown. Intestinal epithelial contact with commensal bacteria and/or their products has been shown to activate noninflammatory signaling pathways, such as extracellular signal-related kinase (ERK), thus influencing homeostatic processes. We previously demonstrated that commensal bacteria stimulate ERK pathway activity via interaction with formyl peptide receptors (FPRs). In the current study, we expand on these findings and show that commensal bacteria initiate ERK signaling through rapid FPR-dependent reactive oxygen species (ROS) generation and subsequent modulation of MAP kinase phosphatase redox status. ROS generation induced by the commensal bacteria Lactobacillus rhamnosus GG and the FPR peptide ligand, N-formyl-Met-Leu-Phe, was abolished in the presence of selective inhibitors for G protein-coupled signaling and FPR ligand interaction. In addition, pretreatment of cells with inhibitors of ROS generation attenuated commensal bacteria-induced ERK signaling, indicating that ROS generation is required for ERK pathway activation. Bacterial colonization also led to oxidative inactivation of the redox-sensitive and ERK-specific phosphatase...

Commensal Bacteria and MAMPs Are Necessary for Stress-Induced Increases in IL-1β and IL-18 but Not IL-6, IL-10 or MCP-1

Maslanik, Thomas; Tannura, Kate; Mahaffey, Lucas; Loughridge, Alice Brianne; Benninson, Lida; Ursell, Luke; Greenwood, Benjamin N.; Knight, Rob; Fleshner, Monika
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 07/12/2012 EN
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Regular interactions between commensal bacteria and the enteric mucosal immune environment are necessary for normal immunity. Alterations of the commensal bacterial communities or mucosal barrier can disrupt immune function. Chronic stress interferes with bacterial community structure (specifically, α-diversity) and the integrity of the intestinal barrier. These interferences can contribute to chronic stress-induced increases in systemic IL-6 and TNF-α. Chronic stress, however, produces many physiological changes that could indirectly influence immune activity. In addition to IL-6 and TNF-α, exposure to acute stressors upregulates a plethora of inflammatory proteins, each having unique synthesis and release mechanisms. We therefore tested the hypothesis that acute stress-induced inflammatory protein responses are dependent on the commensal bacteria, and more specifically, lipopolysaccharide (LPS) shed from Gram-negative intestinal commensal bacteria. We present evidence that both reducing commensal bacteria using antibiotics and neutralizing LPS using endotoxin inhibitor (EI) attenuates increases in some (inflammasome dependent, IL-1 and IL-18), but not all (inflammasome independent, IL-6, IL-10, and MCP-1) inflammatory proteins in the blood of male F344 rats exposed to an acute tail shock stressor. Acute stress did not impact α- or β- diversity measured using 16S rRNA diversity analyses...

Comparison of Adhesin Genes and Antimicrobial Susceptibilities between Uropathogenic and Intestinal Commensal Escherichia coli Strains

Qin, Xiaohua; Hu, Fupin; Wu, Shi; Ye, Xinyu; Zhu, Demei; Zhang, Ying; Wang, Minggui
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 09/04/2013 EN
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The presence of adhesins is arguably an important determinant of pathogenicity for Uropathogenic Escherichia coli (UPEC). Antimicrobial susceptibilities were tested by agar dilution method, fifteen adhesin genes were detected by polymerase chain reaction, and multilocus sequence typing (MLST) was analyzed in 70 UPEC isolates and 41 commensal E. coli strains. Extended-spectrum β-lactamase (ESBL) was determined with confirmatory test. The prevalence of ESBL-producers in UPEC (53%, 37/70) was higher than the commensal intestinal isolates (7%, 3/41), and 97% (36/37) of the ESBL-producing UPEC harbored blaCTX-M genes. afa was present in 36% (10/28) UPEC isolates from recurrent lower urinary tract infection (UTI), and none in the acute pyelonephritis, acute uncomplicated cystitis or commensal strains (P<0.0001). papG was detected in 28% (20/70) of UPEC isolates, while 5% (2/41) of the commensal strains were papG positive (P = 0.0025), and the prevalence of papG was significantly higher in acute pyelonephritis group (71%) than the other two UTI groups (P<0.0001). The prevalence of flu, yqi, yadN and ygiL was significantly higher in UPEC isolates than in the commensal strains. ESBL-producing UPEC showed a lower prevalence of adhesin genes compared with non-ESBL-producing strains. The MLST profiles were different between UPEC and commensal strains...

Identification of Commensal Escherichia coli Genes Involved in Biofilm Resistance to Pathogen Colonization

Da Re, Sandra; Valle, Jaione; Charbonnel, Nicolas; Beloin, Christophe; Latour-Lambert, Patricia; Faure, Philippe; Turlin, Evelyne; Le Bouguénec, Chantal; Renauld-Mongénie, Geneviève; Forestier, Christiane; Ghigo, Jean-Marc
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 07/05/2013 EN
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Protection provided by host bacterial microbiota against microbial pathogens is a well known but ill-understood property referred to as the barrier effect, or colonization resistance. Despite recent genome-wide analyses of host microbiota and increasing therapeutic interest, molecular analysis of colonization resistance is hampered by the complexity of direct in vivo experiments. Here we developed an in vitro-to-in vivo approach to identification of genes involved in resistance of commensal bacteria to exogenous pathogens. We analyzed genetic responses induced in commensal Escherichia coli upon entry of a diarrheagenic enteroaggregative E. coli or an unrelated Klebsiella pneumoniae pathogen into a biofilm community. We showed that pathogens trigger specific responses in commensal bacteria and we identified genes involved in limiting colonization of incoming pathogens within commensal biofilm. We tested the in vivo relevance of our findings by comparing the extent of intestinal colonization by enteroaggregative E. coli and K. pneumoniae pathogens in mice pre-colonized with E. coli wild type commensal strain, or mutants corresponding to identified colonization resistance genes. We demonstrated that the absence of yiaF and bssS (yceP) differentially alters pathogen colonization in the mouse gut. This study therefore identifies previously uncharacterized colonization resistance genes and provides new approaches to unravelling molecular aspects of commensal/pathogen competitive interactions.

Multidrug resistant commensal Escherichia coli in animals and its impact for public health

Szmolka, Ama; Nagy, Béla
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 03/09/2013 EN
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After the era of plentiful antibiotics we are alarmed by the increasing number of antibiotic resistant strains. The genetic flexibility and adaptability of Escherichia coli to constantly changing environments allows to acquire a great number of antimicrobial resistance mechanisms. Commensal strains of E. coli as versatile residents of the lower intestine are also repeatedly challenged by antimicrobial pressures during the lifetime of their host. As a consequence, commensal strains acquire the respective resistance genes, and/or develop resistant mutants in order to survive and maintain microbial homeostasis in the lower intestinal tract. Thus, commensal E. coli strains are regarded as indicators of antimicrobial load on their hosts. This chapter provides a short historic background of the appearance and presumed origin and transfer of antimicrobial resistance genes in commensal intestinal E. coli of animals with comparative information on their pathogenic counterparts. The dynamics, development, and ways of evolution of resistance in the E. coli populations differ according to hosts, resistance mechanisms, and antimicrobial classes used. The most frequent tools of E. coli against a variety of antimicrobials are the efflux pumps and mobile resistance mechanisms carried by plasmids and/or other transferable elements. The emergence of hybrid plasmids (both resistance and virulence) among E. coli is of further concern. Co-existence and co-transfer of these “bad genes” in this huge and most versatile in vivo compartment may represent an increased public health risk in the future. Significance of multidrug resistant (MDR) commensal E. coli seem to be highest in the food animal industry...

Commensal bacteria at the interface of host metabolism and the immune system

Brestoff, Jonathan R; Artis, David
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/2013 EN
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The mammalian gastrointestinal tract, the site of digestion and nutrient absorption, harbors trillions of beneficial commensal microbes from all three domains of life. Commensal bacteria, in particular, are key participants in the digestion of food, and are responsible for the extraction and synthesis of nutrients and other metabolites that are essential for the maintenance of mammalian health. Many of these nutrients and metabolites derived from commensal bacteria have been implicated in the development, homeostasis and function of the immune system, suggesting that commensal bacteria may influence host immunity via nutrient- and metabolite-dependent mechanisms. Here we review the current knowledge of how commensal bacteria regulate the production and bioavailability of immunomodulatory, diet-dependent nutrients and metabolites and discuss how these commensal bacteria-derived products may regulate the development and function of the mammalian immune system.

Differentielle Induktion antimikrobieller Peptide in der Haut durch kommensale und pathogene Staphylokokken; Skin commensal and pathogenic staphylocooci induce antimicrobial peptides differentially

Wanke, Ines
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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Obwohl es zunehmend klinische Evidenz gibt, dass probiotische oder kommensale Bakterien wichtig für die Infektionsabwehr pathogener Mikroorganismen sind, besteht über die zugrundeliegenden biologischen Mechanismen Unklarheit. In der vorliegenden Arbeit konnte gezeigt werden, dass kommensale und pathogene Staphylokokken in primären humanen Keratinozyten die antimikrobiellen Peptide/Proteine HBD-3 und RNase7 unterschiedlich stark induzieren konnten. Dazu aktivierten sie verschiedene Signalwege. S. epidermidis führte nur zu einer geringen Induktion von HBD-3 und RNase7, welche über die TLR2/NFkappaB- und EGFR-Signalwege vermittelt wurde. S .aureus führte hingegen zu einer starken Erhöhung der HBD-3 und RNase7 Expression, die jedoch unabhängig von den genannten Signalwegen erfolgte. Stattdessen war dieses Pathogen in der Lage, den NFkappaB Signalweg zu hemmen, indem der NFkappaB-Inhibitor Ikappab vermehrt exprimiert wurde. Kommensale Staphylokokken waren in der Lage, diese Inhibition des NFkappaB-Signalweges aufzuheben. Dies führte zu einer Amplifikation der antimikrobiellen Antwort der primären humanen Keratinozyten. Somit können die von beiden Staphylokkenspezies aktivierten Signalwege synergistisch zusammenwirken und zu einer verbesserten Infektionsabwehr führen. Im Verlauf dieser Arbeit wurde ein epikutanes Hautinfektionsmodell in der Maus etabliert...

Commensal E. coli Stx2 lysogens produce high levels of phages after spontaneous prophage induction

Iversen, Hildegunn; L' Abée-Lund, Trine M.; Aspholm, Marina; Arnesen, Lotte P. S.; Lindbäck, Toril
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 03/02/2015 EN
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Enterohemorrhagic E. coli (EHEC) is a food-borne pathogen that causes disease ranging from uncomplicated diarrhea to life-threatening hemolytic uremic syndrome (HUS) and nervous system complications. Shiga toxin 2 (Stx2) is the major virulence factor of EHEC and is critical for development of HUS. The genes encoding Stx2 are carried by lambdoid bacteriophages and the toxin production is tightly linked to the production of phages during lytic cycle. It has previously been suggested that commensal E. coli could amplify the production of Stx2-phages and contribute to the severity of disease. In this study we examined the susceptibility of commensal E. coli strains to the Stx2-converting phage ϕ734, isolated from a highly virulent EHEC O103:H25 (NIPH-11060424). Among 38 commensal E. coli strains from healthy children below 5 years, 15 were lysogenized by the ϕ734 phage, whereas lytic infection was not observed. Three of the commensal E. coli ϕ734 lysogens were tested for stability, and appeared stable and retained the phage for at least 10 cultural passages. When induced to enter lytic cycle by H2O2 treatment, 8 out of 13 commensal lysogens produced more ϕ734 phages than NIPH-11060424. Strikingly, five of them even spontaneously (non-induced) produced higher levels of phage than the H2O2 induced NIPH-11060424. An especially high frequency of HUS (60%) was seen among children infected by NIPH-11060424 during the outbreak in 2006. Based on our findings...

Nutritional Basis for Colonization Resistance by Human Commensal Escherichia coli Strains HS and Nissle 1917 against E. coli O157:H7 in the Mouse Intestine

Maltby, Rosalie; Leatham-Jensen, Mary P.; Gibson, Terri; Cohen, Paul S.; Conway, Tyrrell
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 17/01/2013 EN
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Escherichia coli is a single species consisting of many biotypes, some of which are commensal colonizers of mammals and others that cause disease. Humans are colonized on average with five commensal biotypes, and it is widely thought that the commensals serve as a barrier to infection by pathogens. Previous studies showed that a combination of three pre-colonized commensal E. coli strains prevents colonization of E. coli O157:H7 in a mouse model (Leatham, et al., 2010, Infect Immun 77: 2876–7886). The commensal biotypes included E. coli HS, which is known to successfully colonize humans at high doses with no adverse effects, and E. coli Nissle 1917, a human commensal strain that is used in Europe as a preventative of traveler's diarrhea. We hypothesized that commensal biotypes could exert colonization resistance by consuming nutrients needed by E. coli O157:H7 to colonize, thus preventing this first step in infection. Here we report that to colonize streptomycin-treated mice E. coli HS consumes six of the twelve sugars tested and E. coli Nissle 1917 uses a complementary yet divergent set of seven sugars to colonize, thus establishing a nutritional basis for the ability of E. coli HS and Nissle 1917 to occupy distinct niches in the mouse intestine. Together these two commensals use the five sugars previously determined to be most important for colonization of E. coli EDL933...

The Ontogeny of Mucosal and Systemic Antibody Responses to HIV-1 Infection

Trama, Ashley Mead
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2014
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The humoral immune system plays a critical role in the clearance of numerous pathogens. In the setting of HIV-1 infection, the virus infects, integrates its genome into the host's cells, replicates, and establishes a reservoir of virus-infected cells. The initial antibody response to HIV-1 infection is targeted to non-neutralizing epitopes on HIV-1 Env gp41, and when a neutralizing response does develop months after transmission, it is specific for the autologous founder virus and the virus escapes rapidly. After continuous waves of antibody mediated neutralization and viral escape, a small subset of infected individuals eventually develop broad and potent heterologous neutralizing antibodies years after infection. In this dissertation, I have studied the ontogeny of mucosal and systemic antibody responses to HIV-1 infection by means of three distinct aims: 1. Determine the origin of the initial antibody response to HIV-1 infection. 2. Characterize the role of restricted VH and VL gene segment usage in shaping the antibody response to HIV-1 infection. 3. Determine the role of persistence of B cell clonal lineages in shaping the mutation frequencies of HIV-1 reactive antibodies.

After the introduction (Chapter 1) and methods (Chapter 2)...

A new species of Temnocephala (Platyhelminthes, Temnocephalida) commensal of Pomella megastoma (Mollusca, Ampullariidae) from Misiones, Argentina

Damborenea,Cristina; Brusa,Francisco
Fonte: Instituto de Biología Publicador: Instituto de Biología
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2008 EN
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Temnocephala lamothei n. sp., a commensal of Pomella megastoma (Sowerby, 1825), is described herein from specimens collected at Arroyo Yabotí-Miní (Misiones province, Argentina). Juveniles and adults were removed from the mantle cavity by host relaxation. Distinctive characters of the new species are: non-partitioned intestine; conical cirrus with 1 face flat and another concave; distal area with spines, as evidenced by a strong, oblique sclerotized ring, and 2 rows of long spines, an internal one with long spines arising from base of introvert and an external one arising from distal end of the introvert. The closest species are T. iheringi, T. rochensis and T. haswelli, which are also commensals of mollusc species. The presence of this new species of Temnocephala, and its similarity to the other species that are commensals of molluscan species, suggest the existence of a morphologically homogeneous group.