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Di Pilato V, Willison E, Marchese A. The microbiology and pathogenesis of nonfermenting Gram-negative infections. Curr Opin Infect Dis 2023; 36:537-544. [PMID: 37732777 PMCID: PMC10624403 DOI: 10.1097/qco.0000000000000969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
PURPOSE OF REVIEW This review provides an overview of most recent evidence about pathogenesis traits and virulence factors contributing to successful colonization or infection by P. aeruginosa , A. baumannii , S. maltophilia and B. cepacia complex, among the most clinically relevant nonfermenting Gram-negative bacteria (NFGNB). RECENT FINDINGS The growing clinical importance of NFGNB as important opportunistic pathogens causing difficult-to-treat infections in a fragile patients' population in stressed by numerous studies. Identification of novel virulence factors and deciphering of their mechanisms of action have greatly furthered our understanding of NFGNB pathogenesis, revealing that each pathogen-specific armamentarium of virulence factors (adhesins, motility, capsule, biofilm, lipopolysaccharide, exotoxins, exoenzymes, secretion systems, siderophores) can be likely responsible for the difference in the pathophysiology even in the context of a similar infection site. Emerging evidence of the immunomodulatory effect of some virulence factors is also acknowledged. SUMMARY NFGNB continue to be a serious global problem as cause of life-threatening opportunistic infections, owing to a highly heterogeneous content of virulence factors and their extensive number of intrinsic resistance mechanisms. Further efforts in development of novel effective antimicrobials and of alternative strategies targeting key virulence factors are warranted.
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Affiliation(s)
- Vincenzo Di Pilato
- Department of Surgical Sciences and Integrated Diagnostics (DISC), University of Genoa
| | - Edward Willison
- Microbiology Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Anna Marchese
- Department of Surgical Sciences and Integrated Diagnostics (DISC), University of Genoa
- Microbiology Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
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2
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Liu M, Bedouhene S, Hurtado-Nedelec M, Pintard C, Dang PMC, Yu S, El-Benna J. The Prolyl Isomerase Pin1 Controls Lipopolysaccharide-Induced Priming of NADPH Oxidase in Human Neutrophils. Front Immunol 2019; 10:2567. [PMID: 31736979 PMCID: PMC6839773 DOI: 10.3389/fimmu.2019.02567] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 10/16/2019] [Indexed: 11/13/2022] Open
Abstract
Production of superoxide anion and other reactive oxygen species (ROS) by neutrophils has a vital role in host defense against microbes. However, over-production can induce cell injury participating to inflammation. Superoxide anion is produced by the phagocyte NADPH oxidase/NOX2, a multicomponent enzyme system consisting of six proteins: two trans-membrane proteins (gp91 phox and p22 phox ) and four soluble cytosolic proteins (p40 phox , p67 phox , p47 phox , and the small G-proteins, Rac1/2). Phosphorylation of p47 phox on several serines regulates NADPH oxidase activation. LPS released by gram negative bacteria can enhance or prime neutrophil superoxide production in combination with other agonists such as the bacterial peptide formyl-Met-Leu-Phe (fMLP). Since the pathways involved in LPS-induced priming are not completely understood, we investigated the role of the prolyl cis/trans isomerase Pin1 in this process. Two different Pin1 inhibitors, PiB, and Juglone are able to block LPS-induced priming of ROS production by human neutrophils in a concentration dependent manner. PiB and Juglone did not inhibit LPS-induced CD11b translocation neither CD62L shedding. LPS induced an increase of Pin1 activity in neutrophils similar to TNFα and fMLP. Since the phosphorylation of p47 phox on Ser345 is critical for NADPH oxidase up-regulation, we investigated the effect of LPS on this process. Results show that LPS induced the phosphorylation of p47 phox mainly on serine 345 and induced the activation of p38MAPKinase and ERK1/2. These results suggest that the prolyl cis/trans isomerase Pin1 may control LPS-induced priming of superoxide production in human neutrophils. Pharmacological targeting of Pin1 could be a valuable approach in sepsis.
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Affiliation(s)
- Min Liu
- College of Chemical Engineering, Nanjing Forestry University, Nanjing, China.,INSERM U1149, ERL 8252 CNRS, Centre de Recherche sur l'Inflammation, Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, Faculté de Médecine, Site Xavier Bichat, Paris, France.,Yitong Food Industry Co., Ltd, Xuzhou, China
| | - Samia Bedouhene
- Laboratoire de Biochimie Appliquée et de Biotechnologie, Faculté des Sciences Biologiques et des Sciences Agronomiques, Université M. Mammeri, Tizi-Ouzou, Algeria
| | - Margarita Hurtado-Nedelec
- INSERM U1149, ERL 8252 CNRS, Centre de Recherche sur l'Inflammation, Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, Faculté de Médecine, Site Xavier Bichat, Paris, France.,Departement d'Immunologie et d'Hématologie, Unité Dysfonctionnements Immunitaires, Centre Hospitalo-Universitaire Xavier Bichat, Paris, France
| | - Coralie Pintard
- INSERM U1149, ERL 8252 CNRS, Centre de Recherche sur l'Inflammation, Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, Faculté de Médecine, Site Xavier Bichat, Paris, France
| | - Pham My-Chan Dang
- INSERM U1149, ERL 8252 CNRS, Centre de Recherche sur l'Inflammation, Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, Faculté de Médecine, Site Xavier Bichat, Paris, France
| | - Shiyuan Yu
- College of Chemical Engineering, Nanjing Forestry University, Nanjing, China
| | - Jamel El-Benna
- INSERM U1149, ERL 8252 CNRS, Centre de Recherche sur l'Inflammation, Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, Faculté de Médecine, Site Xavier Bichat, Paris, France
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3
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El-Benna J, Hurtado-Nedelec M, Marzaioli V, Marie JC, Gougerot-Pocidalo MA, Dang PMC. Priming of the neutrophil respiratory burst: role in host defense and inflammation. Immunol Rev 2017; 273:180-93. [PMID: 27558335 DOI: 10.1111/imr.12447] [Citation(s) in RCA: 277] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Neutrophils are the major circulating white blood cells in humans. They play an essential role in host defense against pathogens. In healthy individuals, circulating neutrophils are in a dormant state with very low efficiency of capture and arrest on the quiescent endothelium. Upon infection and subsequent release of pro-inflammatory mediators, the vascular endothelium signals to circulating neutrophils to roll, adhere, and cross the endothelial barrier. Neutrophils migrate toward the infection site along a gradient of chemo-attractants, then recognize and engulf the pathogen. To kill this pathogen entrapped inside the vacuole, neutrophils produce and release high quantities of antibacterial peptides, proteases, and reactive oxygen species (ROS). The robust ROS production is also called 'the respiratory burst', and the NADPH oxidase or NOX2 is the enzyme responsible for the production of superoxide anion, leading to other ROS. In vitro, several soluble and particulate agonists induce neutrophil ROS production. This process can be enhanced by prior neutrophil treatment with 'priming' agents, which alone do not induce a respiratory burst. In this review, we will describe the priming process and discuss the beneficial role of controlled neutrophil priming in host defense and the detrimental effect of excessive neutrophil priming in inflammatory diseases.
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Affiliation(s)
- Jamel El-Benna
- INSERM-U1149, CNRS-ERL8252, Centre de Recherche sur l'Inflammation, Paris, France.,Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, DHU FIRE, Faculté de Médecine, Site Xavier Bichat, Université Paris Diderot, Paris, France
| | - Margarita Hurtado-Nedelec
- INSERM-U1149, CNRS-ERL8252, Centre de Recherche sur l'Inflammation, Paris, France.,Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, DHU FIRE, Faculté de Médecine, Site Xavier Bichat, Université Paris Diderot, Paris, France.,Département d'Immunologie et d'Hématologie, UF Dysfonctionnements Immunitaires, HUPNVS, Hôpital Bichat, Paris, France
| | - Viviana Marzaioli
- INSERM-U1149, CNRS-ERL8252, Centre de Recherche sur l'Inflammation, Paris, France.,Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, DHU FIRE, Faculté de Médecine, Site Xavier Bichat, Université Paris Diderot, Paris, France
| | - Jean-Claude Marie
- INSERM-U1149, CNRS-ERL8252, Centre de Recherche sur l'Inflammation, Paris, France.,Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, DHU FIRE, Faculté de Médecine, Site Xavier Bichat, Université Paris Diderot, Paris, France.,Département d'Immunologie et d'Hématologie, UF Dysfonctionnements Immunitaires, HUPNVS, Hôpital Bichat, Paris, France
| | - Marie-Anne Gougerot-Pocidalo
- INSERM-U1149, CNRS-ERL8252, Centre de Recherche sur l'Inflammation, Paris, France.,Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, DHU FIRE, Faculté de Médecine, Site Xavier Bichat, Université Paris Diderot, Paris, France.,Département d'Immunologie et d'Hématologie, UF Dysfonctionnements Immunitaires, HUPNVS, Hôpital Bichat, Paris, France
| | - Pham My-Chan Dang
- INSERM-U1149, CNRS-ERL8252, Centre de Recherche sur l'Inflammation, Paris, France.,Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, DHU FIRE, Faculté de Médecine, Site Xavier Bichat, Université Paris Diderot, Paris, France
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4
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Macrophages, but not neutrophils, are critical for proliferation of Burkholderia cenocepacia and ensuing host-damaging inflammation. PLoS Pathog 2017. [PMID: 28651010 PMCID: PMC5501683 DOI: 10.1371/journal.ppat.1006437] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Bacteria of the Burkholderia cepacia complex (Bcc) can cause devastating pulmonary infections in cystic fibrosis (CF) patients, yet the precise mechanisms underlying inflammation, recurrent exacerbations and transition from chronic stages to acute infection and septicemia are not known. Bcc bacteria are generally believed to have a predominant extracellular biofilm life style in infected CF lungs, similar to Pseudomonas aeruginosa, but this has been challenged by clinical observations which show Bcc bacteria predominantly in macrophages. More recently, Bcc bacteria have emerged in nosocomial infections of patients hospitalized for reasons unrelated to CF. Research has abundantly shown that Bcc bacteria can survive and replicate in mammalian cells in vitro, yet the importance of an intracellular life style during infection in humans is unknown. Here we studied the contribution of innate immune cell types to fatal pro-inflammatory infection caused by B. cenocepacia using zebrafish larvae. In strong contrast to the usual protective role for macrophages against microbes, our results show that these phagocytes significantly worsen disease outcome. We provide new insight that macrophages are critical for multiplication of B. cenocepacia in the host and for development of a fatal, pro-inflammatory response that partially depends on Il1-signalling. In contrast, neutrophils did not significantly contribute to disease outcome. In subcutaneous infections that are dominated by neutrophil-driven phagocytosis, the absence of a functional NADPH oxidase complex resulted in a small but measurably higher increase in bacterial growth suggesting the oxidative burst helps limit bacterial multiplication; however, neutrophils were unable to clear the bacteria. We suggest that paradigm-changing approaches are needed for development of novel antimicrobials to efficiently disarm intracellular bacteria of this group of highly persistent, opportunistic pathogens.
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5
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Hsueh PT, Liu CL, Wang HH, Ni WF, Chen YL, Liu JK. A comparison of the immunological potency of Burkholderia lipopolysaccharides in endotoxemic BALB/c mice. Microbiol Immunol 2017; 60:725-739. [PMID: 27862204 DOI: 10.1111/1348-0421.12450] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 10/25/2016] [Accepted: 11/04/2016] [Indexed: 11/29/2022]
Abstract
Lipopolysaccharide is one of the virulence factors of the soil-borne pathogens Burkholderia pseudomallei, B. thailandensis, B. cenocepacia and B. multivorans, which cause septic melioidosis (often in B. pseudomallei infections but rarely in B. thailandensis infections) or cepacia syndromes (commonly in B. cenocepacia infections but rarely in B. multivorans infections). The inflammatory responses in Burkholderia LPS-induced endotoxemia were evaluated in this study. Prior to induction, the conserved structures and functions of each purified LPS were determined using electrophoretic phenotypes, the ratios of 3-hydroxytetradecanoic to 3-hydroxyhexadecanoic acid and endotoxin units. In an in vitro assay, cytokine expression of myeloid differentiation primary response gene 88 and Toll/IL-1 receptor domain containing adapter-inducing INF-β-dependent signaling-dependent signaling differed when stimulated by different LPS. Endotoxemia was induced in mice by s.c. injection as evidenced by increasing serum concentrations of 3-hydroxytetradecanoic acid and the septic prognostic markers CD62E and ICAM-1. During endotoxemia, splenic CD11b+ I-A+ , CD11b+ CD80+ , CD11b+ CD86+ and CD11b+ CD11c+ subpopulations increased. After induction with B. pseudomallei LPS, there were significant increases in splenic CD49b NK cells and CD14 macrophages. The inflamed CD11b+ CCR2+ , CD11b+ CD31+ , CD11b+ CD14+ , resident CD11b+ CX3 CR1+ and progenitor CD11b+ CD34+ cells showed delayed increases in bone marrow. B. multivorans LPS was the most potent inducer of serum cytokines and chemokines, whereas B. cenocepacia LPS induced relatively low concentrations of the chemokines MIP-1α and MIP-1β. Endotoxin activities did not correlate with the virulence of Burkholderia strains. Thus factors other than LPS and/or other mechanisms of low activity LPS must mediate the pathogenicity of highly virulent Burkholderia strains.
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Affiliation(s)
- Pei-Tan Hsueh
- Department of Biological Sciences, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 80424, Taiwan
| | - Chiu-Lin Liu
- Department of Biotechnology, National Kaohsiung Normal University, 60 Shenjhong Rd., 82446, Kaohsiung, Taiwan
| | - Hsuan-Han Wang
- Department of Biotechnology, National Kaohsiung Normal University, 60 Shenjhong Rd., 82446, Kaohsiung, Taiwan
| | - Wei-Fen Ni
- Department of Biotechnology, National Kaohsiung Normal University, 60 Shenjhong Rd., 82446, Kaohsiung, Taiwan
| | - Ya-Lei Chen
- Department of Biotechnology, National Kaohsiung Normal University, 60 Shenjhong Rd., 82446, Kaohsiung, Taiwan
| | - Jong-Kang Liu
- Department of Biological Sciences, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 80424, Taiwan
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6
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SenGupta S, Hittle LE, Ernst RK, Uriarte SM, Mitchell TC. A Pseudomonas aeruginosa hepta-acylated lipid A variant associated with cystic fibrosis selectively activates human neutrophils. J Leukoc Biol 2016; 100:1047-1059. [PMID: 27538572 DOI: 10.1189/jlb.4vma0316-101r] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 07/20/2016] [Indexed: 12/12/2022] Open
Abstract
Pseudomonas aeruginosa (PA) infection in cystic fibrosis (CF) lung disease causes airway neutrophilia and hyperinflammation without effective bacterial clearance. We evaluated the immunostimulatory activities of lipid A, the membrane anchor of LPS, isolated from mutants of PA that synthesize structural variants, present in the airways of patients with CF, to determine if they correlate with disease severity and progression. In a subset of patients with a severe late stage of CF disease, a unique hepta-acylated lipid A, hepta-1855, is synthesized. In primary human cell cultures, we found that hepta-1855 functioned as a potent TLR4 agonist by priming neutrophil respiratory burst and stimulating strong IL-8 from monocytes and neutrophils. hepta-1855 also had a potent survival effect on neutrophils. However, it was less efficient in stimulating neutrophil granule exocytosis and also less potent in triggering proinflammatory TNF-α response from monocytes. In PA isolates that do not synthesize hepta-1855, a distinct CF-specific adaptation favors synthesis of a penta-1447 and hexa-1685 LPS mixture. We found that penta-1447 lacked immunostimulatory activity but interfered with inflammatory IL-8 synthesis in response to hexa-1685. Together, these observations suggest a potential contribution of hepta-1855 to maintenance of the inflammatory burden in late-stage CF by recruiting neutrophils via IL-8 and promoting their survival, an effect presumably amplified by the absence of penta-1447. Moreover, the relative inefficiency of hepta-1855 in triggering neutrophil degranulation may partly explain the persistence of PA in CF disease, despite extensive airway neutrophilia.
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Affiliation(s)
- Shuvasree SenGupta
- Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, Kentucky, USA
| | - Lauren E Hittle
- Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, Maryland, USA
| | - Robert K Ernst
- Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, Maryland, USA
| | - Silvia M Uriarte
- Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, Kentucky, USA; .,Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky, USA; and
| | - Thomas C Mitchell
- Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, Kentucky, USA;
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7
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Gautam V, Shafiq N, Singh M, Ray P, Singhal L, Jaiswal NP, Prasad A, Singh S, Agarwal A. Clinical and in vitro evidence for the antimicrobial therapy in Burkholderia cepacia complex infections. Expert Rev Anti Infect Ther 2015; 13:629-63. [PMID: 25772031 DOI: 10.1586/14787210.2015.1025056] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Treatment of infections caused by Burkholderia cepacia complex (Bcc) in cystic fibrosis (CF) patients poses a complex problem. Bcc is multidrug-resistant due to innate and acquired mechanisms of resistance. As CF patients receive multiple courses of antibiotics, susceptibility patterns of strains from CF patients may differ from those noted in strains from non-CF patients. Thus, there was a need for assessing in vitro and clinical data to guide antimicrobial therapy in these patients. A systematic search of literature, followed by extraction and analysis of available information from human and in vitro studies was done. The results of the analysis are used to address various aspects like use of antimicrobials for pulmonary and non-pulmonary infections, use of combination versus monotherapy, early eradication, duration of therapy, route of administration, management of biofilms, development of resistance during therapy, pharmacokinetics-pharmacodynamics correlations, therapy in post-transplant patients and newer drugs in Bcc-infected CF patients.
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Affiliation(s)
- Vikas Gautam
- Deparatment of Medical Microbiology, PGIMER, Chandigarh 160022, India
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8
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Lorenzo FD, Sturiale L, Palmigiano A, Fazio LL, Paciello I, Coutinho CP, Sá-Correia I, Bernardini M, Lanzetta R, Garozzo D, Silipo A, Molinaro A. Chemistry and Biology of the Potent Endotoxin from aBurkholderia dolosaClinical Isolate from a Cystic Fibrosis Patient. Chembiochem 2013; 14:1105-15. [DOI: 10.1002/cbic.201300062] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Indexed: 01/10/2023]
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9
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Forier K, Messiaen AS, Raemdonck K, Deschout H, Rejman J, De Baets F, Nelis H, De Smedt SC, Demeester J, Coenye T, Braeckmans K. Transport of nanoparticles in cystic fibrosis sputum and bacterial biofilms by single-particle tracking microscopy. Nanomedicine (Lond) 2013; 8:935-49. [DOI: 10.2217/nnm.12.129] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Aim: The aim of this study was to evaluate the effect of the surface functionalization of model nanoparticles on their mobility in bacterial biofilms and cystic fibrosis sputum. Materials & methods: With single-particle tracking microscopy, the mobility of 0.1- and 0.2-µm fluorescent polyethylene glycol (PEG) modified, carboxylate- and N,N-dimethylethylenediamine-modified polystyrene nanospheres were evaluated in fresh cystic fibrosis sputum, as well as Burkholderia multivorans and Pseudomonas aeruginosa biofilms. Results: PEGylation increased the mobility of the particles in sputum and biofilms, while the charged nanospheres were strongly immobilized. However, the transport of the PEGylated nanoparticles was lower in sputum compared with biofilms. Furthermore, the particle transport showed heterogeneity in samples originating from different patients. Conclusion: This study’s data suggest that for future nanocarrier design it will be essential to combine PEGylation with a targeting moiety to ensure sufficient mobility in mucus and a better accumulation of the nanoparticles in the biofilm. Original submitted 14 February 2012; Revised submitted 24 July 2012; Published online 5 October 2012
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Affiliation(s)
- Katrien Forier
- Ghent University, Harelbekestraat 72, 9000 Ghent, Ghent, Belgium
- Center for Nano- and Biophotonics, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium
| | | | - Koen Raemdonck
- Ghent University, Harelbekestraat 72, 9000 Ghent, Ghent, Belgium
| | - Hendrik Deschout
- Ghent University, Harelbekestraat 72, 9000 Ghent, Ghent, Belgium
- Center for Nano- and Biophotonics, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium
| | - Joanna Rejman
- Ghent University, Harelbekestraat 72, 9000 Ghent, Ghent, Belgium
| | - Frans De Baets
- Department of Pediatrics, University Hospital of Ghent, De Pintelaan 185, 9000 Ghent, Ghent, Belgium
| | - Hans Nelis
- Ghent University, Harelbekestraat 72, 9000 Ghent, Ghent, Belgium
| | | | - Joseph Demeester
- Ghent University, Harelbekestraat 72, 9000 Ghent, Ghent, Belgium
| | - Tom Coenye
- Ghent University, Harelbekestraat 72, 9000 Ghent, Ghent, Belgium
| | - Kevin Braeckmans
- Ghent University, Harelbekestraat 72, 9000 Ghent, Ghent, Belgium
- Center for Nano- and Biophotonics, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium
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10
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Wright C, Pilkington R, Callaghan M, McClean S. Activation of MMP-9 by human lung epithelial cells in response to the cystic fibrosis-associated pathogen Burkholderia cenocepacia reduced wound healing in vitro. Am J Physiol Lung Cell Mol Physiol 2011; 301:L575-86. [PMID: 21743026 DOI: 10.1152/ajplung.00226.2010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Burkholderia cepacia complex is a group of bacterial pathogens that cause opportunistic infections in cystic fibrosis (CF). The most virulent of these is Burkholderia cenocepacia. Matrix metalloproteinases (MMPs) are upregulated in CF patients. The aim of this work was to examine the role of MMPs in the pathogenesis of B. cepacia complex, which has not been explored to date. Real-time PCR analysis showed that B. cenocepacia infection upregulated MMP-2 and MMP-9 genes in the CF lung cell line CFBE41o- within 1 h, whereas MMP-2, -7, and -9 genes were upregulated in the non-CF lung cell line 16HBE14o-. Conditioned media from both cell lines showed increased MMP-9 activation following B. cenocepacia infection. Conditioned media from B. cenocepacia-infected cells significantly reduced the rate of wound healing in confluent lung epithelia (P < 0.05), in contrast to conditioned media from Pseudomonas aeruginosa-infected cells, which showed predominant MMP-2 activation. Treatment of control conditioned media from both cell lines with the MMP activator 4-aminophenylmercuric acetate (APMA) also resulted in clear activation of MMP-9 and to a much lesser extent MMP-2. APMA treatment of control media also delayed the repair of wound healing in confluent epithelial cells. Furthermore, specific inhibition of MMP-9 in medium from cells exposed to B. cenocepacia completely reversed the delay in wound repair. These data suggest that MMP-9 plays a role in the reduced epithelial repair observed in response to B. cenocepacia infection and that its activation following B. cenocepacia infection contributes to the pathogenesis of this virulent pathogen.
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Affiliation(s)
- Ciara Wright
- Centre of Microbial Host Interactions, Institute of Technology Tallaght, Dublin, Ireland
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11
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Kotrange S, Kopp B, Akhter A, Abdelaziz D, Abu Khweek A, Caution K, Abdulrahman B, Wewers MD, McCoy K, Marsh C, Loutet SA, Ortega X, Valvano MA, Amer AO. Burkholderia cenocepacia O polysaccharide chain contributes to caspase-1-dependent IL-1beta production in macrophages. J Leukoc Biol 2010; 89:481-8. [PMID: 21178113 DOI: 10.1189/jlb.0910513] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Burkholderia cenocepacia infections in CF patients involve heightened inflammation, fatal sepsis, and high antibiotic resistance. Proinflammatory IL-1β secretion is important in airway inflammation and tissue damage. However, little is known about this pathway in macrophages upon B. cenocepacia infection. We report here that murine macrophages infected with B. cenocepacia K56-2 produce proinflammatory cytokine IL-1β in a TLR4 and caspase-1-mediated manner. We also determined that the OPS (O antigen) of B. cenocepacia LPS contributes to IL-1β production and pyroptotic cell death. Furthermore, we showed that the malfunction of the CFTR channel augmented IL-1β production upon B. cenocepacia infection of murine macrophages. Taken together, we identified eukaryotic and bacterial factors that contribute to inflammation during B. cenocepacia infection, which may aid in the design of novel approaches to control pulmonary inflammation.
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Affiliation(s)
- Sheetal Kotrange
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Center for Microbial Interface Biology and the Department of Internal Medicine, Ohio State University, Columbus, Ohio 43210, USA
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12
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Mil-Homens D, Rocha EPC, Fialho AM. Genome-wide analysis of DNA repeats in Burkholderia cenocepacia J2315 identifies a novel adhesin-like gene unique to epidemic-associated strains of the ET-12 lineage. Microbiology (Reading) 2010; 156:1084-1096. [DOI: 10.1099/mic.0.032623-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Members of the Burkholderia cepacia complex (Bcc) are respiratory pathogens in patients with cystic fibrosis (CF). Close repetitive DNA sequences often associate with surface antigens to promote genetic variability in pathogenic bacteria. The genome of Burkholderia cenocepacia J2315, a CF isolate belonging to the epidemic lineage Edinburgh–Toronto (ET-12), was analysed for the presence of close repetitive DNA sequences. Among the 422 DNA close repeats, 45 genes potentially involved in virulence were identified and grouped into 12 classes; of these, 13 genes were included in the antigens class. Two trimeric autotransporter adhesins (TAA) among the 13 putative antigens are absent from the other Burkholderia genomes and are clustered downstream of the cci island that is a marker for transmissible B. cenocepacia strains. This cluster contains four adhesins, one outer-membrane protein, one sensor histidine kinase and two transcriptional regulators. By using PCR, we analysed three genes among 47 Bcc isolates to determine whether the cluster was conserved. These three genes were present in the isolates of the ET-12 lineage but absent in all the other members. Furthermore, the BCAM0224 gene was exclusively detected in this epidemic lineage and may serve as a valuable new addition to the field of Bcc diagnostics. The BCAM0224 gene encodes a putative TAA that demonstrates adhesive properties to the extracellular matrix protein collagen type I. Quantitative real-time PCR analysis indicated that BCAM0224 gene expression occurred preferentially for cells grown under high osmolarity, oxygen-limited conditions and oxidative stress. Inactivation of BCAM0224 in B. cenocepacia attenuates the ability of the mutant to promote cell adherence in vitro and impairs the overall bacterial virulence against Galleria mellonella as a model of infection. Together, our data show that BCAM0224 from B. cenocepacia J2315 represents a new collagen-binding TAA with no bacterial orthologues which has an important role in cellular adhesion and virulence.
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Affiliation(s)
- Dalila Mil-Homens
- IBB-Institute for Biotechnology and Bioengineering, Center for Biological and Chemical Engineering, Instituto Superior Técnico, Lisbon 1049-001, Portugal
| | - Eduardo P. C. Rocha
- Microbial Evolutionary Genomics Group, CNRS URA2171, Institute Pasteur, F-75015 Paris, France
- Atelier de Bioinformatique, Université Pierre et Marie Curie-Paris 6, Paris, F-75005 France
| | - Arsenio M. Fialho
- IBB-Institute for Biotechnology and Bioengineering, Center for Biological and Chemical Engineering, Instituto Superior Técnico, Lisbon 1049-001, Portugal
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13
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De Soyza A, Silipo A, Lanzetta R, Govan JR, Molinaro A. Chemical and biological features of Burkholderia cepacia complex lipopolysaccharides. Innate Immun 2008; 14:127-44. [PMID: 18562572 DOI: 10.1177/1753425908093984] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The Burkholderia cepacia complex comprises 10 closely related Gram-negative organisms all of which appear capable of causing disease in humans. These organisms appear of particular relevance to patients with cystic fibrosis. Lipopolysaccharide (LPS) is an important virulence determinant in Gram-negative pathogens. In this review, we highlight important data within the field commenting on LPS/lipid A structure-to-function relationships and cytokine induction capacity of Burkholderia strains studied so far.
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Affiliation(s)
- Anthony De Soyza
- Transplantation and Immunobiology Group, Institute of Cellular Medicine, Newcastle University and The Freeman Hospital, Newcastle-upon-Tyne, UK.
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14
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Neugebauer H, Hartmann P, Krenn S, Glück T, Schölmerich J, Straub R, Wiest R. Bacterial translocation increases phagocytic activity of polymorphonuclear leucocytes in portal hypertension: priming independent of liver cirrhosis. Liver Int 2008; 28:1149-57. [PMID: 18662280 DOI: 10.1111/j.1478-3231.2008.01829.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
AIM Bacterial translocation (BT) to mesenteric lymph nodes (MLN) in cirrhosis has been linked to impaired host defence. Phagocytosis by polymorphonuclear leucocytes (PMNLs) is the primary event in the killing of bacteria but has not been investigated in relation to the presence of BT. METHODS Mesenteric lymph nodes were harvested sterile and assessed for BT by culture techniques. Study groups included ascitic cirrhotic rats (LC), healthy controls (Con) as well as portal-vein-ligated (PVL) rats 2 days (acute PVL with and without norfloxacin) or 3 weeks after surgery (chronic PVL). PMNLs were isolated from systemic blood and the capacity to phagocytose opsonized Escherichia coli was evaluated by FACS analysis. RESULTS No BT was observed in Con and chronic PVL animals but 11/20 LC (55%) and six out of six acute PVL (100%) presented with BT. In the presence of BT, PMNL from PVL as well as LC rats showed significantly increased phagocytic activity as compared with controls. In contrast, PMNL from animals without BT, whether PVL or LC, exhibited phagocytic activity similar to those from control rats. The number of PMNLs involved in the phagocytic process was significantly increased only in portal-hypertensive rats with but not without BT as compared with controls. Norfloxacin did prevent BT in acute PVL animals, thereby correcting the increase in phagocytic capacity in PMNL. CONCLUSIONS Cirrhosis per se is not associated with alterations of the phagocytic capacity of PMNL. The occurrence of BT, however, increases the phagocytic capacity of PMNL, being observed likewise in prehepatic portal hypertension, indicating an in vivo'priming' of PMNL by BT independent of cirrhosis.
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Affiliation(s)
- Hermann Neugebauer
- Department of Internal Medicine, School of Medicine, University Hospital, Regensburg 93042, Germany
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15
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Hung RJ, Chien HS, Lin RZ, Lin CT, Vatsyayan J, Peng HL, Chang HY. Comparative analysis of two UDP-glucose dehydrogenases in Pseudomonas aeruginosa PAO1. J Biol Chem 2007; 282:17738-48. [PMID: 17442666 DOI: 10.1074/jbc.m701824200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
UDP-glucose dehydrogenase (UGDH) catalyzes a two-step NAD(+)-dependent oxidation of UDP-glucose to produce UDP-glucuronic acid, which is a common substrate for the biosynthesis of exopolysaccharide. Searching the Pseudomonas aeruginosa PAO1 genome data base for a UGDH has helped identify two open reading frames, PA2022 and PA3559, which may encode a UGDH. To elucidate their enzymatic identity, the two genes were cloned and overexpressed in Escherichia coli, and the recombinant proteins were purified. Both the gene products are active as dimers and are capable of utilizing UDP-glucose as a substrate to generate UDP-glucuronic acid. The K(m) values of PA2022 and PA3559 for UDP-glucose are approximately 0.1 and 0.4 mM, whereas the K(m) values for NAD(+) are 0.5 and 2.0 mM, respectively. Compared with PA3559, PA2022 exhibits broader substrate specificity, utilizing TDP-glucose and UDP-N-acetylglucosamine with one-third the velocity of that with UDP-glucose. The PA2022 mutant and PA2022-PA3559 double mutant, but not the PA3559 mutant, are more susceptible to chloramphenicol, cefotaxime, and ampicillin. The PA3559 mutant, however, shows a reduced resistance to polymyxin B compared with wild type PAO1. Finally, real time PCR analysis indicates that PA3559 is expressed primarily in low concentrations of Mg(2+), which contrasts with the constitutive expression of PA2022. Although both the enzymes catalyze the same reaction, their enzymatic properties and gene expression profiles indicate that they play distinct physiological roles in P. aeruginosa, as reflected by different phenotypes displayed by the mutants.
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Affiliation(s)
- Ruei-Jiun Hung
- Institute of Molecular Medicine, National Tsing Hua University, Hsin Chu 300, Taiwan
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16
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Govan JRW, Brown AR, Jones AM. Evolving epidemiology of Pseudomonas aeruginosa and the Burkholderia cepacia complex in cystic fibrosis lung infection. Future Microbiol 2007; 2:153-64. [PMID: 17661652 DOI: 10.2217/17460913.2.2.153] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The morbidity and mortality of patients with cystic fibrosis (CF) is primarily determined by chronic and debilitating lung infections caused by a surprisingly narrow spectrum of bacterial pathogens. Pseudomonas aeruginosa is by far the most prevalent life-threatening CF pathogen. In the absence of aggressive early therapy, it infects the majority of adult patients and determines long-term survival. The epidemiology of CF pulmonary infections continues to evolve. Amongst the most recent CF pathogens to have emerged are a group of closely related bacteria, known as the Burkholderia cepacia complex. These organisms are a particular challenge due to inherent antibiotic resistance, the potential for patient-to-patient spread, and the risk of ‘cepacia syndrome’, a rapid fulminating pneumonia sometimes accompanied by bacteremia. Strict cross-infection control was prompted by early epidemiological experience of the B. cepacia complex and is essential in the management of all CF pathogens.
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Affiliation(s)
- John R W Govan
- University of Edinburgh, Cystic Fibrosis Group, Centre for Infectious Diseases, Edinburgh, UK.
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17
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Bamford S, Ryley H, Jackson SK. Highly purified lipopolysaccharides from Burkholderia cepacia complex clinical isolates induce inflammatory cytokine responses via TLR4-mediated MAPK signalling pathways and activation of NFkappaB. Cell Microbiol 2006; 9:532-43. [PMID: 17002785 DOI: 10.1111/j.1462-5822.2006.00808.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In cystic fibrosis (CF), bacteria of the Burkholderia cepacia complex (Bcc) can induce a fulminant inflammation with pneumonitis and sepsis. Lipopolysaccharide (LPS) may be an important virulence factor associated with this decline but little is known about the molecular pathogenesis of Bcc LPS. In this study we have investigated the inflammatory response to highly purified LPS from different Bcc clinical isolates and the cellular signalling pathways employed. The inflammatory response (TNFalpha, IL-6) was measured in human MonoMac 6 monocytes and inhibition experiments were used to investigate the Toll-like receptors and associated adaptor molecules and pathways utilized. LPS from all clinical Bcc isolates induced significant pro-inflammatory cytokines and utilized TLR4 and CD14 to mediate activation of mitogen-activated protein kinase pathways, IkappaB-alpha degradation and NFkappaB activation. However, LPS from different clinical isolates of the same clonal strain of Burkholderia cenocepacia were found to induce a varied inflammatory response. LPS from clinical isolates of Burkholderia multivorans was found to activate the inflammatory response via MyD88-independent pathways. This study suggests that LPS alone from clinical isolates of Bcc is an important virulence factor in CF and utilizes TLR4-mediated signalling pathways to induce a significant inflammatory response.
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Affiliation(s)
- Sarah Bamford
- Department of Medical Microbiology, School of Medicine, Cardiff University, Cardiff, UK
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18
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Zen K, Reaves TA, Soto I, Liu Y. Response to genistein: Assaying the activation status and chemotaxis efficacy of isolated neutrophils. J Immunol Methods 2006; 309:86-98. [PMID: 16412456 DOI: 10.1016/j.jim.2005.11.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Revised: 11/17/2005] [Accepted: 11/18/2005] [Indexed: 12/15/2022]
Abstract
Neutrophil (PMN) activation and chemotaxis toward inflammatory stimuli play critical roles in host defense and tissue inflammation. To determine the molecular mechanisms that regulate PMN function, many studies currently employ in vitro PMN activation and transmigration assays using freshly isolated peripheral PMN or PMN isolated from bone marrow. However, due to the highly sensitive nature of PMN, cell activation or priming can occur during isolation, which demands assay(s) that ensure the consistency of isolated PMN prior to using them in subsequent experiments. Here, we introduce a simple screening assay based on the observation that in transmigration assays, isolated PMN differentially respond to the tyrosine kinase inhibitor genistein and this is related to their activation status. As shown, we observed that isolated PMN for which early migration is enhanced by genistein have an overall high transmigration efficacy and that over 80% of applied PMN migrate across collagen-coated filters in a 2 h time period. Conversely, the inhibitory/non-enhancement effect of genistein is accompanied by a poor PMN transmigration, with less than 25% of applied PMN transmigrating across. Further analysis of PMN spontaneous adhesion, degranulation and cell surface CD11b/CD18 expression suggests that reduced migration of PMN is associated with PMN activation/priming that happens, in most cases, during the in vitro cell isolation procedure regardless of the blood donor. Thus, based on these observations, we developed a "genistein assay" to directly predict PMN status after each isolation. From our experience, this assay has not only revealed new insights into the mechanisms of PMN activation and assisted in functional assays, but it has also provided a method that can be mastered by both inexperienced and experienced researchers to assay isolated PMN and thus avoid using inconsistent cells (e.g. pre-activated PMN) in their experiments.
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Affiliation(s)
- Ke Zen
- Department of Pathology, Emory University, Atlanta, GA 30322, USA
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19
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Coenye T, Vandamme P. Overrepresentation of immunostimulatory CpG motifs in Burkholderia genomes. J Cyst Fibros 2005; 4:193-6. [PMID: 15963770 DOI: 10.1016/j.jcf.2005.03.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2005] [Revised: 02/02/2005] [Accepted: 03/23/2005] [Indexed: 10/25/2022]
Abstract
Pulmonary infections with Burkholderia cepacia complex organisms contribute significantly to morbidity and mortality in patients with cystic fibrosis (CF), partially due to the intense inflammatory response of the host to the presence of bacteria and their byproducts. In the present study we show that Burkholderia genomes contain a large number of immunostimulatory CpG motifs. This is mainly because of their large genome size. This suggests that DNA from Burkholderia sp. has the potential to cause significant inflammatory response. Whether this contributes significantly to the airway inflammation often observed in infected CF patients remains to be determined.
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Affiliation(s)
- Tom Coenye
- Laboratorium voor Farmaceutische, Microbiologie, Universiteit Gent, Belgium.
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20
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Bylund J, Burgess LA, Cescutti P, Ernst RK, Speert DP. Exopolysaccharides from Burkholderia cenocepacia inhibit neutrophil chemotaxis and scavenge reactive oxygen species. J Biol Chem 2005; 281:2526-32. [PMID: 16316987 DOI: 10.1074/jbc.m510692200] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacteria belonging to the Burkholderia cepacia complex are important opportunistic pathogens in compromised hosts, particularly patients with cystic fibrosis or chronic granulomatous disease. Isolates of B. cepacia complex may produce large amounts of exopolysaccharides (EPS) that endow the bacteria with a mucoid phenotype and appear to facilitate bacterial persistence during infection. We showed that EPS from a clinical B. cenocepacia isolate interfered with the function of human neutrophils in vitro; it inhibited chemotaxis and production of reactive oxygen species (ROS), both essential components of innate neutrophil-mediated host defenses. These inhibitory effects were not due to cytotoxicity or interference with intracellular calcium signaling. EPS also inhibited enzymatic generation of ROS in cell-free systems, indicating that it scavenges these bactericidal products. B. cenocepacia EPS is structurally distinct from Pseudomonas aeruginosa alginate, yet they share the capacity to scavenge ROS and inhibit chemotaxis. These properties could explain why the two bacterial species resist clearance from the infected cystic fibrosis lung.
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Affiliation(s)
- Johan Bylund
- Department of Pediatrics, University of British Columbia, Child and Family Research Institute, Vancouver, British Columbia V5Z 4H4, Canada
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21
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Brockbank S, Downey D, Elborn JS, Ennis M. Effect of cystic fibrosis exacerbations on neutrophil function. Int Immunopharmacol 2005; 5:601-8. [PMID: 15683855 DOI: 10.1016/j.intimp.2004.11.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2004] [Revised: 07/19/2004] [Accepted: 11/09/2004] [Indexed: 11/18/2022]
Abstract
In cystic fibrosis (CF), inflammation is caused by persistent bacterial infection from Pseudomonas aeruginosa and Burkholderia cenocepacia in the lung and is characterised by the persistent infiltration of massive numbers of neutrophils which leads to lung injury. The aim of this present study was to investigate the effects of CF exacerbations on the reactivity of peripheral blood neutrophils compared to data from a normal healthy control population. Peripheral blood neutrophils were isolated from control subjects and CF patients before and after an exacerbation of their lung disease. Isolated neutrophils were stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) and phorbol 12-myristate 13-acetate (PMA) and the rate of superoxide generation and elastase activity measured and compared with neutrophils from healthy age-matched controls. Neutrophils from CF patients spontaneously generated higher levels of superoxide after resolution of the exacerbation compared to control neutrophils. The stimulated generation of superoxide from control neutrophils was not significantly different from neutrophils isolated from CF patients either before or after resolution of the CF exacerbation. Neutrophils from CF patients spontaneously released more elastase than control neutrophils but released less elastase than control neutrophils in response to fMLP. The stimulated release of elastase from neutrophils was not significantly different before compared to after resolution of the exacerbation. Neutrophils from CF patients displayed a different pattern of response than those from control subjects; however, CF exacerbations did not appear to modulate neutrophil function.
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Affiliation(s)
- Simon Brockbank
- Respiratory Research Group, Inflammation Research Centre, The Queen's University of Belfast, Northern Ireland, UK
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22
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Mahenthiralingam E, Urban TA, Goldberg JB. The multifarious, multireplicon Burkholderia cepacia complex. Nat Rev Microbiol 2005; 3:144-56. [PMID: 15643431 DOI: 10.1038/nrmicro1085] [Citation(s) in RCA: 616] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The Burkholderia cepacia complex (Bcc) is a collection of genetically distinct but phenotypically similar bacteria that are divided into at least nine species. Bcc bacteria are found throughout the environment, where they can have both beneficial and detrimental effects on plants and some members can also degrade natural and man-made pollutants. Bcc bacteria are now recognized as important opportunistic pathogens that can cause variable lung infections in cystic fibrosis patients, which result in asymptomatic carriage, chronic infection or 'cepacia syndrome', which is characterized by a rapid decline in lung function that can include invasive disease. Here we highlight the unique characteristics of the Bcc, focusing on the factors that determine virulence.
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23
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McManus TE, McDowell A, Moore JE, Elborn SJ. Organisms isolated from adults with cystic fibrosis. Ann Clin Microbiol Antimicrob 2004; 3:26. [PMID: 15601468 PMCID: PMC544565 DOI: 10.1186/1476-0711-3-26] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2004] [Accepted: 12/15/2004] [Indexed: 11/18/2022] Open
Abstract
Background Patients with cystic fibrosis [CF] have frequent pulmonary exacerbations associated with the isolation of bacterial organisms from sputum samples. It is not clear however, if there are differences in the types of additional organisms isolated from patients who are infected with Burkholderia cepacia complex [BCC] or Pseudomonas aerugionsa [PA] in comparison to those who are not infected with either of these organisms [NI]. Methods Adult patients attending the regional CF unit were followed over a two year period and patients were assigned to three groups depending on whether they were known to be chronically infected with BCC, PA or NI. We compared the numbers and types of organisms which were isolated in each of these groups. Results Information was available on a total of 79 patients; BCC 23, PA 30 and NI 26. Total numbers of organisms isolated, expressed as median and IQR for each group, [P = 0.045] and numbers of co-infecting organisms [P = 0.003] were significantly higher in the BCC group compared to PA, and in the PA group [P < 0.001, p = 0.007 respectively] compared to NI patients. The pattern of co-infecting organisms was similar in all three groups. Conclusions Total numbers of organisms isolated and numbers of co-infecting organisms were significantly higher in the BCC group compared to PA, and in the PA group compared to NI patients. Types of co-infecting organisms are similar in all groups of patients.
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Affiliation(s)
- Terence E McManus
- Regional Adult Cystic Fibrosis Center, Belfast City Hospital, Belfast, Northern Ireland, BT9 7AB, UK
| | - Andrew McDowell
- Department of Bacteriology, Belfast City Hospital, Belfast, Northern Ireland, BT9 7AB, UK
| | - John E Moore
- Department of Bacteriology, Belfast City Hospital, Belfast, Northern Ireland, BT9 7AB, UK
| | - Stuart J Elborn
- Regional Adult Cystic Fibrosis Center, Belfast City Hospital, Belfast, Northern Ireland, BT9 7AB, UK
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25
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De Soyza A, Ellis CD, Khan CMA, Corris PA, Demarco de Hormaeche R. Burkholderia cenocepaciaLipopolysaccharide, Lipid A, and Proinflammatory Activity. Am J Respir Crit Care Med 2004; 170:70-7. [PMID: 15044201 DOI: 10.1164/rccm.200304-592oc] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Organisms from the Burkholderia cepacia complex are important pathogens in cystic fibrosis and are associated with increased rates of sepsis and death. These organisms comprise nine closely related species known as genomovars. B. cenocepacia (genomovar III) is the most prevalent and appears the most virulent. We investigated the biological activity of a reference panel of strains using whole-cell lysates to induce septic-shock related cytokines from differentiated human monocytic cells. We found varying biological activity within and between genomovars, with B. cenocepacia strains possessing the greatest cytokine induction activity. This activity was CD-14 dependent, suggesting that LPS was responsible for the cytokine induction. Cytokine induction was not simply related to the expression of rough or smooth LPS. We purified LPS from two strains, B. cenocepacia LMG 12614 and B. multivorans LMG 14273, each possessing rough LPS. Divergence in biological activity of the two genomovars was preserved when human monocytic cells were stimulated with purified LPS. Lipid A purified from LMG 14273 and LMG 12614 were analyzed by matrix-assisted laser desorption ionization/time of flight mass spectrometry. Lipid A from the less effective cytokine inducer LMG 14273 was found to be missing a beta-hydroxymyristate (3-OH C14:0) relative to the lipid A of B. cenocepacia LMG 12614.
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Affiliation(s)
- Anthony De Soyza
- Transplantation and Immunobiology group, The Freeman Hospital, High Heaton, Newcastle-upon-Tyne NE7 7DN, United Kingdom.
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26
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Sprong T, Møller ASW, Bjerre A, Wedege E, Kierulf P, van der Meer JWM, Brandtzaeg P, van Deuren M, Mollnes TE. Complement activation and complement-dependent inflammation by Neisseria meningitidis are independent of lipopolysaccharide. Infect Immun 2004; 72:3344-9. [PMID: 15155639 PMCID: PMC415700 DOI: 10.1128/iai.72.6.3344-3349.2004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2003] [Revised: 01/21/2004] [Accepted: 02/19/2004] [Indexed: 11/20/2022] Open
Abstract
Fulminant meningococcal sepsis has been termed the prototypical lipopolysaccharide (LPS)-mediated gram-negative septic shock. Systemic inflammation by activated complement and cytokines is important in the pathogenesis of this disease. We investigated the involvement of meningococcal LPS in complement activation, complement-dependent inflammatory effects, and cytokine or chemokine production. Whole blood anticoagulated with lepirudin was stimulated with wild-type Neisseria meningitidis H44/76 (LPS+), LPS-deficient N. meningitidis H44/76lpxA (LPS-), or purified meningococcal LPS (NmLPS) at concentrations that were relevant to meningococcal sepsis. Complement activation products, chemokines, and cytokines were measured by enzyme-linked immunosorbent assays, and granulocyte CR3 (CD11b/CD18) upregulation and oxidative burst were measured by flow cytometry. The LPS+ and LPS- N. meningitidis strains both activated complement effectively and to comparable extents. Purified NmLPS, used at a concentration matched to the amount present in whole bacteria, did not induce any complement activation. Both CR3 upregulation and oxidative burst were also induced, independent of LPS. Interleukin-1beta (IL-1beta), tumor necrosis factor alpha, and macrophage inflammatory protein 1alpha production was predominantly dependent on LPS, in contrast to IL-8 production, which was also markedly induced by the LPS- meningococci. In this whole blood model of meningococcal sepsis, complement activation and the immediate complement-dependent inflammatory effects of CR3 upregulation and oxidative burst occurred independent of LPS.
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Affiliation(s)
- Tom Sprong
- Department of General Internal Medicine, University Medical Centre St. Radboud Nijmegen, Nijmegen, The Netherlands.
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27
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Allan ND, Kooi C, Sokol PA, Beveridge TJ. Putative virulence factors are released in association with membrane vesicles from Burkholderia cepacia. Can J Microbiol 2004; 49:613-24. [PMID: 14663495 DOI: 10.1139/w03-078] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Like many other Gram-negative bacteria, Burkholderia cepacia naturally releases membrane vesicles (n-MVs) during normal growth. Through filtration and differential centrifugation, n-MVs from clinical isolates of the IIIa and V genomovars were isolated and their characteristics compared. Electron microscopy revealed that they were spherical, 30-220 nm in diameter, and bilayered. Virulence factors thought to play a role in pathogenicity (e.g., lipase, phospholipase-N, and protease, including a metalloprotease) were found associated with n-MVs, while peptidoglycan zymogram analysis also revealed 26, 28, 36, and 66 kDa peptidoglycan-degrading enzymes. n-MVs were often contaminated with flagella and pili when isolated by traditional methods, and a new strategy using a linear isopycnic sucrose gradient was utilized. For better characterization, this was applied to a representative genomovar IIIa strain (C5424) and showed that n-MVs consisted of a subset of specific outer membrane and periplasmic proteins as well as lipopoly saccharide possessing only a putative minor O-side chain polymer. This finding suggests that certain components are selected by B. cepacia during n-MV formation, and since some are putative virulence factors, this property could help deliver the factors to tissue, thereby aiding infection.
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Affiliation(s)
- Nick D Allan
- Canadian Bacterial Disease Network--National Centre of Excellence, Department of Microbiology, College of Biological Science, University of Guelph, ON
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28
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Affiliation(s)
- John R W Govan
- Cystic Fibrosis Microbiology Laboratory and Strain Repository, Medical Microbiology Division, University of Edinburgh Medical School, Teviot Place, Edinburgh, EH8 9AG, UK.
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29
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State of the art: why do the lungs of patients with cystic fibrosis become infected and why can't they clear the infection? Respir Res 2003; 4:8. [PMID: 14511398 PMCID: PMC203156 DOI: 10.1186/1465-9921-4-8] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2003] [Accepted: 08/27/2003] [Indexed: 12/19/2022] Open
Abstract
Cystic Fibrosis (CF) lung disease, which is characterized by airway obstruction, chronic bacterial infection, and an excessive inflammatory response, is responsible for most of the morbidity and mortality. Early in life, CF patients become infected with a limited spectrum of bacteria, especially P. aeruginosa. New data now indicate that decreased depth of periciliary fluid and abnormal hydration of mucus, which impede mucociliary clearance, contribute to initial infection. Diminished production of the antibacterial molecule nitric oxide, increased bacterial binding sites (e.g., asialo GM-1) on CF airway epithelial cells, and adaptations made by the bacteria to the airway microenvironment, including the production of virulence factors and the ability to organize into a biofilm, contribute to susceptibility to initial bacterial infection. Once the patient is infected, an overzealous inflammatory response in the CF lung likely contributes to the host's inability to eradicate infection. In response to increased IL-8 and leukotriene B4 production, neutrophils infiltrate the lung where they release mediators, such as elastase, that further inhibit host defenses, cripple opsonophagocytosis, impair mucociliary clearance, and damage airway wall architecture. The combination of these events favors the persistence of bacteria in the airway. Until a cure is discovered, further investigations into therapies that relieve obstruction, control infection, and attenuate inflammation offer the best hope of limiting damage to host tissues and prolonging survival.
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Langley R, Kenna DT, Vandamme P, Ure R, Govan JRW. Lysogeny and bacteriophage host range within the Burkholderia cepacia complex. J Med Microbiol 2003; 52:483-490. [PMID: 12748267 DOI: 10.1099/jmm.0.05099-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Burkholderia cepacia complex comprises a group of nine closely related species that have emerged as life-threatening pulmonary pathogens in immunocompromised patients, particularly individuals with cystic fibrosis or chronic granulomatous disease. Attempts to explain the genomic plasticity, adaptability and virulence of the complex have paid little attention to bacteriophages, particularly the potential contribution of lysogenic conversion and transduction. In this study, lysogeny was observed in 10 of 20 representative strains of the B. cepacia complex. Three temperate phages and five lytic phages isolated from soils, river sediments or the plant rhizosphere were chosen for further study. Six phages exhibited T-even morphology and two were lambda-like. The host range of individual phages, when tested against 66 strains of the B. cepacia complex and a representative panel of other pseudomonads, was not species-specific within the B. cepacia complex and, in some phages, included Burkholderia gladioli and Pseudomonas aeruginosa. These new data indicate a potential role for phages of the B. cepacia complex in the evolution of these soil bacteria as pathogens of plants, humans and animals, and as novel therapeutic agents.
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Affiliation(s)
- Ross Langley
- Department of Medical Microbiology, University of Edinburgh, Teviot Place, Edinburgh EH8 9AG, UK 2Laboratorium voor Mikrobiologie, Faculteit Wetenschappen, Universiteit Gent, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium#dReceived 11 October 2002 Accepted 12 February 2003
| | - Dervla T Kenna
- Department of Medical Microbiology, University of Edinburgh, Teviot Place, Edinburgh EH8 9AG, UK 2Laboratorium voor Mikrobiologie, Faculteit Wetenschappen, Universiteit Gent, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium#dReceived 11 October 2002 Accepted 12 February 2003
| | - Peter Vandamme
- Department of Medical Microbiology, University of Edinburgh, Teviot Place, Edinburgh EH8 9AG, UK 2Laboratorium voor Mikrobiologie, Faculteit Wetenschappen, Universiteit Gent, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium#dReceived 11 October 2002 Accepted 12 February 2003
| | - Rebecca Ure
- Department of Medical Microbiology, University of Edinburgh, Teviot Place, Edinburgh EH8 9AG, UK 2Laboratorium voor Mikrobiologie, Faculteit Wetenschappen, Universiteit Gent, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium#dReceived 11 October 2002 Accepted 12 February 2003
| | - John R W Govan
- Department of Medical Microbiology, University of Edinburgh, Teviot Place, Edinburgh EH8 9AG, UK 2Laboratorium voor Mikrobiologie, Faculteit Wetenschappen, Universiteit Gent, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium#dReceived 11 October 2002 Accepted 12 February 2003
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Kenna DT, Barcus VA, Langley RJ, Vandamme P, Govan JRW. Lack of correlation between O-serotype, bacteriophage susceptibility and genomovar status in the Burkholderia cepacia complex. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 2003; 35:87-92. [PMID: 12628542 DOI: 10.1016/s0928-8244(02)00442-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The Burkholderia cepacia complex comprises at least nine phylogenetically related genomic species (genomovars) which cause life-threatening infection in immunocompromised humans, particularly individuals with cystic fibrosis or chronic granulomatous disease. Prior to recognition that 'B. cepacia' comprise multiple species, in vitro studies revealed that the lipopolysaccharide (LPS) of these Gram-negative bacteria is strongly endotoxic. In this study, we used 117 B. cepacia complex isolates to determine if there is a correlation between O-antigen serotype and genomovar status. Isolates were also tested for their ability to act as bacterial hosts for the LPS-binding bacteriophages NS1 and NS2. The absence of genomovar II (Burkholderia multivorans) in 'historical B. cepacia' isolates was notable. Neither O-serotype nor phage susceptibility correlated with genomovar status. We conclude that variability in LPS may contribute to the success of these highly adaptable bacteria as human pathogens.
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Affiliation(s)
- Dervla T Kenna
- Cystic Fibrosis Laboratory, Medical Microbiology, University of Edinburgh Medical School, Teviot Place, Edinburgh EH8 9AG, UK.
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Tomich M, Griffith A, Herfst CA, Burns JL, Mohr CD. Attenuated virulence of a Burkholderia cepacia type III secretion mutant in a murine model of infection. Infect Immun 2003; 71:1405-15. [PMID: 12595458 PMCID: PMC148827 DOI: 10.1128/iai.71.3.1405-1415.2003] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Type III secretion systems are utilized by a number of gram-negative bacterial pathogens to deliver virulence-associated proteins into host cells. Using a PCR-based approach, we identified homologs of type III secretion genes in the gram-negative bacterium Burkholderia cepacia, an important pulmonary pathogen in immunocompromised patients and patients with cystic fibrosis. One of the genes, designated bscN, encodes a member of a family of ATP-binding proteins believed to generate energy driving virulence protein secretion. Genetic dissection of the regions flanking the bscN gene revealed a locus consisting of at least 10 open reading frames, predicted to encode products with significant homology to known type III secretion proteins in other bacteria. A defined null mutation was generated in the bscN gene, and the null strain and wild-type parent strain were examined by use of a murine model of B. cepacia infection. Quantitative bacteriological analysis of the lungs and spleens of infected C57BL/6 mice revealed that the bscN null strain was attenuated in virulence compared to the parent strain, with significantly lower bacterial recovery from the lungs and spleens at 3 days postinfection. Moreover, histopathological changes, including an inflammatory cell infiltrate, were more pronounced in the lungs of mice infected with the wild-type parent strain than in those of mice infected with the isogenic bscN mutant. These results implicate type III secretion as an important determinant in the pathogenesis of B. cepacia.
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Affiliation(s)
- Mladen Tomich
- Department of Microbiology, University of Minnesota, Minneapolis, Minnesota 55455-0312, USA
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Gronow S, Noah C, Blumenthal A, Lindner B, Brade H. Construction of a deep-rough mutant of Burkholderia cepacia ATCC 25416 and characterization of its chemical and biological properties. J Biol Chem 2003; 278:1647-55. [PMID: 12427755 DOI: 10.1074/jbc.m206942200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Burkholderia cepacia is a bacterium with increasing importance as a pathogen in patients with cystic fibrosis. The deep-rough mutant Ko2b was generated from B. cepacia type strain ATCC 25416 by insertion of a kanamycin resistance cassette into the gene waaC encoding heptosyltransferase I. Mass spectrometric analysis of the de-O-acylated lipopolysaccharide (LPS) of the mutant showed that it consisted of a bisphosphorylated glucosamine backbone with two 3-hydroxyhexadecanoic acids in amide-linkage, 4-amino-4-deoxyarabinose (Ara4N) residues on both phosphates, and a core oligosaccharide of the sequence Ara4N-(1 --> 8) D-glycero-D-talo-oct-2-ulosonic acid (Ko)-(2 --> 4)3-deoxy-D-manno-oct-2-ulosonic acid (Kdo). The mutant allowed investigations on the biosynthesis of the LPS as well as on its role in human infection. Mutant Ko2b showed no difference in its ability to invade human macrophages as compared with the wild type. Furthermore, isolated LPS of both strains induced the production of tumor necrosis factor alpha from macrophages to the same extent. Thus, the truncation of the LPS did not decrease the biological activity of the mutant or its LPS in these aspects.
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Affiliation(s)
- Sabine Gronow
- Division of Medical and Biochemical Microbiology, Research Center Borstel, Center for Medicine and Biosciences, Parkallee 22, D-23845 Borstel, Germany.
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Segal BH, Ding L, Holland SM. Phagocyte NADPH oxidase, but not inducible nitric oxide synthase, is essential for early control of Burkholderia cepacia and chromobacterium violaceum infection in mice. Infect Immun 2003; 71:205-10. [PMID: 12496167 PMCID: PMC143145 DOI: 10.1128/iai.71.1.205-210.2003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Reactive oxygen and nitrogen intermediates have critical, partially overlapping roles in host defense against a variety of pathogens. Using mice deficient in generating phagocyte superoxide (p47(phox)(-/-)) and mice deficient in generating inducible nitric oxide synthase (iNOS(-/-)), we examined the roles of these reactive species in host defense against Burkholderia cepacia and Chromobacterium violaceum, organisms known to have unusual virulence in chronic granulomatous disease. Intraperitoneal B. cepacia challenge (4.0 x 10(3) to 4.0 x 10(5) organisms/mouse) resulted in mortality in all p47(phox)(-/-) mice, with the survival interval being inversely proportionate to the amount of inoculum. Pretreatment with gamma interferon did not affect survival. C. violaceum was strikingly virulent in p47(phox)(-/-) mice (the 50% lethal dose [LD(50)] was <13 organisms). iNOS(-/-) and wild-type mice were resistant to B. cepacia challenges of at least 10(6) organisms per mouse, and the LD(50) of C. violaceum was between 10(6) and 10(7) organisms per mouse. Consistent with the survival data, numbers of organisms in cultures of B. cepacia from multiple sites were higher for p47(phox)(-/-) mice than for iNOS(-/-) and wild-type mice at day 4 after challenge, but numbers of organisms for different B. cepacia strains varied. The recovery of C. violaceum was strikingly greater at 18 h after challenge for p47(phox)(-/-) mice than for iNOS(-/-) and wild-type mice, in which the organism burdens were virtually nil. In vitro, both B. cepacia and C. violaceum were sensitive to H(2)O(2) and to reactive nitrogen intermediates but the sensitivities of different strains varied significantly. Host defense against B. cepacia and C. violaceum is critically dependent in vivo on reactive oxygen intermediates, and these species are model organisms to further dissect host and pathogen interactions related to the generation and scavenging of microbicidal reactive intermediates.
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Affiliation(s)
- Brahm H Segal
- Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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Chu KK, Davidson DJ, Halsey TK, Chung JW, Speert DP. Differential persistence among genomovars of the Burkholderia cepacia complex in a murine model of pulmonary infection. Infect Immun 2002; 70:2715-20. [PMID: 11953418 PMCID: PMC127911 DOI: 10.1128/iai.70.5.2715-2720.2002] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cystic fibrosis patients infected with strains from different genomovars of the Burkholderia cepacia complex can experience diverse clinical outcomes. To identify genomovar-specific determinants that might be responsible for these differences, we developed a pulmonary model of infection in BALB/c mice. Mice were rendered leukopenic by administration of cyclophosphamide prior to intranasal challenge with 1.6 x 10(4) bacteria. Five of six genomovar II strains persisted at stable numbers in the lungs until day 16 with minimal toxicity, whereas zero of seven genomovar III strains persisted but resulted in variable toxicity. We have developed a chronic pulmonary model of B. cepacia infection which reveals differences among genomovars in terms of clinical infection outcome.
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Affiliation(s)
- Karen K Chu
- Department of Paediatrics, University of British Columbia, Vancouver, British Columbia, Canada
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36
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Abstract
Cystic fibrosis is the most common lethal inherited disorder with autosomal recessive inheritance. Major progress has been made in understanding the molecular mechanisms leading to increased susceptibility to Pseudomonas aeruginosa colonization. Persistent respiratory infection with P. aeruginosa leads to progressive pulmonary inflammation and is the major cause of morbidity and mortality. Treatment and prophylaxis of respiratory infection has improved the median survival and quality of life of cystic fibrosis patients. In the future, treatment of the underlying genetic defect may be possible.
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Abstract
Previous studies have indicated that pulmonary infection with Burkholderia cepacia is associated with poor clinical outcome after lung transplantation in cystic fibrosis (CF). Many treatment centers consider B. cepacia infection an absolute contraindication to lung transplantation. However, the B. cepacia complex actually consists of several closely related bacterial species. Although each of these has been isolated from CF sputum culture, certain species are much more frequently recovered than others, and it is not yet clear whether all species have the same potential for virulence in CF. Additional study is needed to better define the relative risks associated with each species of the B. cepacia complex.
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Affiliation(s)
- J J LiPuma
- Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, Michigan 48109-0646, USA.
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Sajjan U, Thanassoulis G, Cherapanov V, Lu A, Sjolin C, Steer B, Wu YJ, Rotstein OD, Kent G, McKerlie C, Forstner J, Downey GP. Enhanced susceptibility to pulmonary infection with Burkholderia cepacia in Cftr(-/-) mice. Infect Immun 2001; 69:5138-50. [PMID: 11447196 PMCID: PMC98610 DOI: 10.1128/iai.69.8.5138-5150.2001] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Progressive pulmonary infection is the dominant clinical feature of cystic fibrosis (CF), but the molecular basis for this susceptibility remains incompletely understood. To study this problem, we developed a model of chronic pneumonia by repeated instillation of a clinical isolate of Burkholderia cepacia (genomovar III, ET12 strain), an opportunistic gram-negative bacterium, from a case of CF into the lungs of Cftr (m1unc-/-) (Cftr(-/-)) and congenic Cftr(+/+) controls. Nine days after the last instillation, the CF transmembrane regulator knockout mice showed persistence of viable bacteria with chronic severe bronchopneumonia while wild-type mice remained healthy. The histopathological changes in the lungs of the susceptible Cftr(-/-) mice were characterized by infiltration of a mixed inflammatory-cell population into the peribronchiolar and perivascular spaces, Clara cell hyperplasia, mucus hypersecretion in airways, and exudation into alveolar airspaces by a mixed population of macrophages and neutrophils. An increased proportion of neutrophils was observed in bronchoalveolar lavage fluid from the Cftr(-/-) mice, which, despite an increased bacterial load, demonstrated minimal evidence of activation. Alveolar macrophages from Cftr(-/-) mice also demonstrated suboptimal activation. These observations suggest that the pulmonary host defenses are compromised in lungs from animals with CF, as manifested by increased susceptibility to bacterial infection and lung injury. This murine model of chronic pneumonia thus reflects, in part, the situation in human patients and may help elucidate the mechanisms leading to defective host defense in CF.
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Affiliation(s)
- U Sajjan
- Research Institute, The Hospital for Sick Children, Toronto, Ontario M5G 1X8
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Shimomura H, Matsuura M, Saito S, Hirai Y, Isshiki Y, Kawahara K. Lipopolysaccharide of Burkholderia cepacia and its unique character to stimulate murine macrophages with relative lack of interleukin-1beta-inducing ability. Infect Immun 2001; 69:3663-9. [PMID: 11349028 PMCID: PMC98363 DOI: 10.1128/iai.69.6.3663-3669.2001] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipopolysaccharide (LPS) of Burkholderia cepacia was purified by the conventional phenol-water extraction method (preparation BcLPS-1), followed by enzymatic treatments with DNase, RNase, trypsin, and proteinase K (preparation BcLPS-2), and finally by deoxycholate-phenol-water extraction (preparation BcLPS-3). Cells of LPS-hyporesponsive C3H/HeJ mice were activated by both the BcLPS-1 and the BcLPS-2 preparations but barely activated by BcLPS-3. When LPS-responsive C3H/HeN mice were used as targets, endotoxic activities such as lethal toxicity to galactosamine-sensitized mice, mitogenicity to spleen cells, and activation of macrophages to induce tumor necrosis factor alpha and interleukin-6 (IL-6) were strongly exhibited even by highly purified BcLPS-3 at levels comparable to those of the highly active enterobacterial LPS of Salmonella enterica serovar Abortus-equi (SaeLPS), used as the control. The ability of BcLPS-3 to activate murine macrophages for induction of IL-1beta was, however, much weaker than that of SaeLPS. Both accumulation of pro-IL-1beta protein and expression of IL-1beta mRNA in macrophages by stimulation with BcLPS-3 were much weaker than by stimulation with SaeLPS. These results indicate that LPS of B. cepacia has the potential to play a role as a pathogenic factor with strong activity comparable to that of usual enterobacterial LPS, but unlike the latter, this LPS has a relative lack of ability in the activation of murine macrophages to induce IL-1beta. The lack of IL-1beta-inducing ability appears to be caused by incomplete signal transduction somewhere in the upstream step(s) of IL-1beta gene transcription.
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Affiliation(s)
- H Shimomura
- Department of Microbiology, Jichi Medical School, Tochigi 329-0498, Japan
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Smalley JW, Charalabous P, Birss AJ, Hart CA. Detection of heme-binding proteins in epidemic strains of Burkholderia cepacia. CLINICAL AND DIAGNOSTIC LABORATORY IMMUNOLOGY 2001; 8:509-14. [PMID: 11329449 PMCID: PMC96092 DOI: 10.1128/cdli.8.3.509-514.2001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A panel of 30 previously characterized strains representing five genomovars from the Burkholderia cepacia complex (E. Mahenthiralingam, T. Coenye, J. W. Chung, D. P. Speert, J. R. W. Govan, P. Taylor, and P. Vandamme, J. Clin. Microbiol. 38:910--913, 2000) were examined for their iron protoporphyrin IX-binding ability. These included B. cepacia genomovars I and III and B. stabilis (formerly B. cepacia genomovar IV), B. multivorans (formerly B. cepacia genomovar II), and B. vietnamiensis (formerly B. cepacia genomovar V). Cells were exposed to micro-oxo bisheme of iron protoporphyrin IX (micro-oxo dimers) and examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing, nondenaturing conditions for the presence of heme-binding proteins using tetramethylbenzidine-H(2)O(2) staining. Seven of the 30 strains, each belonging to B. cepacia genomovar III and designated epidemic (in possessing the B. cepacia epidemic strain marker), expressed a 96- to 100-kDa heme-binding protein which was located in the outer membrane. The heme-binding protein of B. cepacia genomovar III epidemic strain C5424 bound iron(III) protoporphyrin IX in both the monomeric and micro-oxo bisheme forms. Cells of all strains grown on Columbia agar bound iron protoporphyrin IX in the micro-oxo bisheme (dimeric) form. There were no statistical differences between the five genomovars, or those possessing the heme-binding protein, in their micro-oxo bisheme-binding ability. Possession of the outer membrane heme-binding protein may be a pathogenicity trait in enabling the bacterium to withstand oxidative stresses in inflammatory exudates in the lung and may aid identification of invasive epidemic strains of B. cepacia.
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Affiliation(s)
- J W Smalley
- Department of Clinical Dental Sciences, The University of Liverpool, Liverpool, United Kingdom.
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Abstract
The Gram-negative bacterium Burkholderia cepacia has recently emerged as an important opportunistic pathogen in humans. This review focuses on the cellular aspects of B. cepacia infection and the dynamics of the B. cepacia-host cell interaction, including recent advances in our understanding of the ability of B. cepacia to adhere to, enter, and survive intracellularly within human cells.
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Affiliation(s)
- C D Mohr
- Department of Microbiology, University of Minnesota Medical School, Minneapolis Minnesota, 55455-0312, USA.
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Berriatua E, Ziluaga I, Miguel-Virto C, Uribarren P, Juste R, Laevens S, Vandamme P, Govan JR. Outbreak of subclinical mastitis in a flock of dairy sheep associated with Burkholderia cepacia complex infection. J Clin Microbiol 2001; 39:990-4. [PMID: 11230416 PMCID: PMC87862 DOI: 10.1128/jcm.39.3.990-994.2001] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An outbreak of subclinical mastitis in a flock of 620 milking sheep was investigated. Microbiological and epidemiological analyses identified the causative agent as belonging to the Burkholderia cepacia complex (formerly Pseudomonas cepacia). Every ewe in the milking flock was individually tested for subclinical mastitis on two separate occasions, 6 weeks apart, by the California (rapid) mastitis test (CMT). The proportion of CMT-positive ewes was 69 of 393 (17.6%) on the first sampling and 27 of 490 (5.5%) on the second sampling. Pure B. cepacia cultures identified with the API 20 NE system were grown from 64 of 96 (66.7%) CMT-positive ewes and from 1 of 33 (3.0%) CMT-negative ewes. Statistical analysis confirmed the significant association between a positive CMT result and a positive culture result for B. cepacia complex. Additional polyphasic taxonomic analyses of eight isolates showed that seven belonged to B. cepacia genomovar III; the remaining isolate was identified as Burkholderia vietnamiensis (formerly B. cepacia genomovar V). Bacteriological investigation of samples from milking equipment and other environmental sites failed to identify "B. cepacia" in any of the samples taken. To our knowledge, this is the first report of an outbreak of natural infection in animals caused by B. cepacia complex and the first description of B. cepacia complex infection in sheep.
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Affiliation(s)
- E Berriatua
- Sanidad Animal, Instituto Vasco de Investigación y Desarrollo Agrario (NEIKER), 48160 Derio, Bizkaia, Spain.
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Lefebre M, Valvano M. In vitro resistance of Burkholderia cepacia complex isolates to reactive oxygen species in relation to catalase and superoxide dismutase production. MICROBIOLOGY (READING, ENGLAND) 2001; 147:97-109. [PMID: 11160804 DOI: 10.1099/00221287-147-1-97] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Burkholderia cepacia complex comprises groups of genomovars (genotypically distinct strains with very similar phenotypes) that have emerged as important opportunistic pathogens in cystic fibrosis (CF) patients. The inflammatory response against bacteria in the airways of CF individuals is dominated by polymorphonuclear cells and involves the generation of oxidative stress, which leads to further inflammation and tissue damage. Bacterial catalase, catalase-peroxidase and superoxide dismutase activities may contribute to the survival of B. cepacia following exposure to reactive oxygen metabolites generated by host cells in response to infection. In the present study the authors investigated the production of catalase, peroxidase and SOD by isolates belonging to various genomovars of the B. cepacia complex. Production of both catalase and SOD was maximal during late stationary phase in almost all isolates examined. Native PAGE identified 13 catalase electrophoretotypes and two SOD electrophoretotypes (corresponding to an Fe-SOD class) in strains belonging to the six genomovars of the B. cepacia complex. Seven out of 11 strains displaying high-level survival after H(2)O(2) treatment in vitro had a bifunctional catalase/peroxidase, and included all the genomovar III strains examined. These isolates represent most of the epidemic isolates that are often associated with the cepacia syndrome. The majority of the isolates from all the genomovars were resistant to extracellular O(-)(2), while resistance to intracellularly generated O(-)(2)was highly variable and could not be correlated with the detected levels of SOD activity. Altogether the results suggest that resistance to toxic oxygen metabolites from extracellular sources may be a factor involved in the persistence of B. cepacia in the airways of CF individuals.
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Affiliation(s)
- M Lefebre
- Departments of Microbiology and Immunology, and Medicine, The University of Western Ontario, London, Ontario, Canada
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Sajjan US, Sylvester FA, Forstner JF. Cable-piliated Burkholderia cepacia binds to cytokeratin 13 of epithelial cells. Infect Immun 2000; 68:1787-95. [PMID: 10722565 PMCID: PMC97349 DOI: 10.1128/iai.68.4.1787-1795.2000] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although the Burkholderia cepacia complex consists of several genomovars, one highly transmissible strain of B. cepacia has been isolated from the sputa of cystic fibrosis (CF) patients throughout the United Kingdom and Canada. This strain expresses surface cable (Cbl) pili and is thought to be the major strain associated with the fatal "cepacia syndrome." In the present report we characterize the specific 55-kDa buccal epithelial cell (BEC) protein that binds cable pilus-positive B. cepacia. N-terminal sequences of CNBr-generated internal peptides identified the protein as cytokeratin 13 (CK13). Western blots of BEC extracts probed with a specific monoclonal antibody to CK13 confirmed the identification. Mixed epidermal cytokeratins (which contain CK13), cytokeratin extract from BEC (which consists essentially of CK13 and CK4), and a polyclonal antibody to mixed cytokeratins inhibited B. cepacia binding to CK13 blots and to normal human bronchial epithelial (NHBE) cells. Preabsorption of the antikeratin antibody with the BEC cytokeratin fraction reversed the inhibitory effect of the antibody. A cytokeratin mixture lacking CK13 was ineffective as an inhibitor of binding. Colocalization of CK13 and B. cepacia by confocal microscopy demonstrated that intact nonpermeabilized NHBE cells express small amounts of surface CK13 and bind Cbl-positive B. cepacia in the same location. Binding to intact NHBE cells was dependent on bacterial concentration and was saturable, whereas a Cbl-negative isolate exhibited negligible binding. These findings raise the possibility that surface-accessible CK13 in respiratory epithelia may be a biologically relevant target for the binding of cable piliated B. cepacia.
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Affiliation(s)
- U S Sajjan
- Research Institute, Division of Structural Biology, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
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Hendry J, Butler S, Elborn JS, Govan JR, Nelson J, Shale DJ, Webb AK. Antibody response to Burkholderia cepacia in patients with cystic fibrosis colonized with Burkholderia cepacia and Pseudomonas aeruginosa. J Infect 2000; 40:164-70. [PMID: 10841094 DOI: 10.1053/jinf.1999.0626] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
INTRODUCTION This study was designed to determine the relationship between formation of serum antibodies to lipopolysaccharide (LPS) core antigen of Burkholderia cepacia and pulmonary colonization with B. cepacia and Pseudomonas aeruginosa in patients with cystic fibrosis (CF), and to define if an enhanced host humoral immune response to B. cepacia was related to a poor clinical outcome. METHODS Serum IgG to B. cepacia LPS core antigen was measured in adult cystic fibrosis patients colonized with B. cepacia and P. aeruginosa, and serial titres were measured in 13 B. cepacia and 41 P. aeruginosa colonized patients followed prospectively over 18 months. RESULTS The median B. cepacia antibody titre was significantly greater in the patients colonized with B. cepacia compared to those colonized with P. aeruginosa, a group which grew B. cepacia intermittently from their sputum. and nine healthy controls. The median antibody titre at recruitment into the study was significantly greater in patients who later went into exacerbations compared with those who remained clinically stable. but there was no difference between B. cepacia antibody titres in patients who died and those who survived the study duration. DISCUSSION The degree of overlap of serum IgG levels to B. cepacia LPS core antigen in cystic fibrosis patients colonized with B. cepacia and P. aeruginosa does not allow this antibody to be used in a clinical context to define infection status. The magnitude of the humoral response to B. cepacia may influence occurrence of pulmonary exacerbations, but a more exuberant humoral immune response to B. cepacia core LPS is not the mechanism by which pulmonary deterioration occurs.
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Affiliation(s)
- J Hendry
- Bradbury Cystic Fibrosis Unit, Wythenshawe Hospital, Manchester, UK
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Hutchison ML, Bonell EC, Poxton IR, Govan JR. Endotoxic activity of lipopolysaccharides isolated from emergent potential cystic fibrosis pathogens. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 2000; 27:73-7. [PMID: 10617793 DOI: 10.1111/j.1574-695x.2000.tb01414.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Improved antimicrobial therapies against the classical spectrum of pathogenic bacteria which colonise the lungs of cystic fibrosis (CF) patients has resulted in improved life expectancy and quality of life. Bacterial species that are resistant to a broad range of antibiotics including Stenotrophomonas maltophilia and Alcaligenes xylosoxidans have now emerged as potential new pathogens to fill the niche. At present, it is unclear from clinical data whether these microbes are commensal or pathogenic. In this study we have quantified the inflammatory potential of lipopolysaccharide (LPS) from eight species of Gram-negative organisms which have been cultured with increasing frequency from CF patients. Inflammatory responses induced by LPS from whole human blood and a human-derived monocyte cell line (THP-1) were assessed. Enzyme-linked immunosorbent assays were used to detect interleukin-6, interleukin-8, and tumour necrosis factor alpha (TNF). A bioassay was also used to assess TNF activity. With the exception of S. maltophilia, LPS extracted from all of the bacteria tested upregulated, by varying degrees, expression of each of the proinflammatory cytokines assayed. This study represents the first comprehensive report of the endotoxic potential of a new wave of microbes which are associated with CF.
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Affiliation(s)
- M L Hutchison
- Department of Medical Microbiology, University of Edinburgh Medical School, Teviot Place, Edinburgh, UK
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Saini LS, Galsworthy SB, John MA, Valvano MA. Intracellular survival of Burkholderia cepacia complex isolates in the presence of macrophage cell activation. MICROBIOLOGY (READING, ENGLAND) 1999; 145 ( Pt 12):3465-3475. [PMID: 10627044 DOI: 10.1099/00221287-145-12-3465] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Strains of the Burkholderia cepacia complex have emerged as a serious threat to patients with cystic fibrosis due to their ability to infect the lung and cause, in some patients, a necrotizing pneumonia that is often lethal. It has recently been shown that several strains of the B. cepacia complex can escape intracellular killing by free-living amoebae following phagocytosis. In this work, the ability of two B. cepacia complex strains to resist killing by macrophages was explored. Using fluorescence microscopy, electron microscopy and a modified version of the gentamicin-protection assay, we demonstrate that B. cepacia CEP021 (genomovar VI), and Burkholderia vietnamiensis (previously B. cepacia genomovar V) CEP040 can survive in PU5-1.8 murine macrophages for a period of at least 5 d without significant bacterial replication. Furthermore, bacterial entry into macrophages stimulated production of tumour necrosis factor and primed them to release toxic oxygen radicals following treatment with phorbol myristoyl acetate. These effects were probably caused by bacterial LPS, as they were blocked by polymyxin B. Infected macrophages primed with interferon gamma produced less nitric oxide than interferon-gamma-primed uninfected cells. We propose that the ability of B. cepacia to resist intracellular killing by phagocytic cells may play a role in the pathogenesis of cystic fibrosis lung infection. Our data are consistent with a model where repeated cycles of phagocytosis and cellular activation without bacterial killing may promote a deleterious inflammatory response causing tissue destruction and decay of lung function.
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Affiliation(s)
- Lalit S Saini
- Department of Microbiology and Immunology1 and Department of Medicine2, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Sara B Galsworthy
- Department of Microbiology and Immunology1 and Department of Medicine2, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Michael A John
- Department of Microbiology and Infection Control, London Health Sciences Centre, London, Ontario, N6A 4G5, Canada3
- Department of Microbiology and Immunology1 and Department of Medicine2, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Miguel A Valvano
- Department of Microbiology and Immunology1 and Department of Medicine2, University of Western Ontario, London, Ontario, N6A 5C1, Canada
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Abstract
Cystic fibrosis patients are exceptionally prone to colonisation by a narrow spectrum of pathogenic bacteria. Since pulmonary infection presently, and for the foreseeable future, plays such a major role in CF lung disease, we review the microbes that are classically associated with CF and the virulence, inflammatory potential and resistance mechanisms which contribute to the reduction in life expectancy for colonised CF patients.
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Affiliation(s)
- M L Hutchison
- Cystic Fibrosis Laboratory, Department of Medical Microbiology, University of Edinburgh Medical School, Teviot Place, Edinburgh EH8 9AG, Scotland, UK
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Speert DP, Steen B, Halsey K, Kwan E. A murine model for infection with Burkholderia cepacia with sustained persistence in the spleen. Infect Immun 1999; 67:4027-32. [PMID: 10417170 PMCID: PMC96694 DOI: 10.1128/iai.67.8.4027-4032.1999] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Burkholderia cepacia is an opportunistic pathogen that causes severe systemic infections in patients with chronic granulomatous disease (CGD) or with cystic fibrosis (CF), but its mechanisms of virulence are poorly understood. We developed a murine model of systemic infection in wild-type (WT) and gamma interferon knockout (GKO) BALB/c mice to facilitate dissection of components of pathogenicity and host defense. Both WT and GKO mice were susceptible to chronic splenic infection with B. cepacia, but not with Pseudomonas aeruginosa. B. cepacia strains from patients with CGD persisted longer than those from CF patients. C57BL/6 mice were the most susceptible murine strain; bacteria persisted in the spleen for 2 months. DBA/2, BALB/c, and A/J strains of mice were relatively resistant to infection. Certain strains of B. cepacia complex can persist in the murine spleen after systemic infection; this may provide clues to its virulence in compromised hosts, such as those with CGD and CF.
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Affiliation(s)
- D P Speert
- Division of Infectious and Immunological Diseases, Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4.
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Zughaier SM, Ryley HC, Jackson SK. A melanin pigment purified from an epidemic strain of Burkholderia cepacia attenuates monocyte respiratory burst activity by scavenging superoxide anion. Infect Immun 1999; 67:908-13. [PMID: 9916107 PMCID: PMC96403 DOI: 10.1128/iai.67.2.908-913.1999] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The acquisition of Burkholderia cepacia in some cystic fibrosis patients is associated with symptoms of acute pulmonary inflammation that may be life threatening. The ability of lipopolysaccharide (LPS) from B. cepacia to prime a monocyte cell line for enhanced superoxide anion generation was investigated and compared with the priming activities of LPSs from Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Escherichia coli. The human monocyte cell line MonoMac-6 (MM6) was primed overnight with different LPSs (100 ng/ml), and the respiratory burst was triggered by exposure to opsonized zymosan (125 micrograms/ml). Superoxide generation was detected by enhanced chemiluminescence with Lucigenin. B. cepacia LPS was found to prime MM6 cells to produce more superoxide anion than P. aeruginosa or S. maltophilia LPS, and this priming response was CD14 dependent. In addition, the inhibition of respiratory burst responses in monocytes by a bacterial melanin-like pigment purified from an epidemic B. cepacia strain was investigated. The melanin-like pigment was isolated from tyrosine-enriched media on which B. cepacia had been grown and was purified by gel filtration, anion ion-exchange chromatography, and ethanol precipitation. The scavenging potential of the melanin-like pigment for superoxide anion radical (*O2-) generated during the respiratory burst was confirmed with superoxide produced from a cell-free system with xanthine-xanthine oxidase and detected by electron paramagnetic resonance spectroscopy with the spin trap 5-diethoxyphosphoryl-5-methyl-1-pyrroline-n-oxide. The addition of melanin during the LPS priming stage had no effect on the subsequent triggering of the respiratory burst, but melanin inhibited *O2- detection when added at the triggering stage of the respiratory burst. We conclude that melanin-producing B. cepacia may derive protection from the free-radical-scavenging properties of this pigment.
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Affiliation(s)
- S M Zughaier
- Department of Medical Microbiology, University of Wales College of Medicine, Cardiff CF4 4XN, United Kingdom
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