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Nakayama-Imaohji H, Hirota K, Yamasaki H, Yoneda S, Nariya H, Suzuki M, Secher T, Miyake Y, Oswald E, Hayashi T, Kuwahara T. DNA Inversion Regulates Outer Membrane Vesicle Production in Bacteroides fragilis. PLoS One 2016; 11:e0148887. [PMID: 26859882 PMCID: PMC4747536 DOI: 10.1371/journal.pone.0148887] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 01/25/2016] [Indexed: 02/06/2023] Open
Abstract
Phase changes in Bacteroides fragilis, a member of the human colonic microbiota, mediate variations in a vast array of cell surface molecules, such as capsular polysaccharides and outer membrane proteins through DNA inversion. The results of the present study show that outer membrane vesicle (OMV) formation in this anaerobe is also controlled by DNA inversions at two distantly localized promoters, IVp-I and IVp-II that are associated with extracellular polysaccharide biosynthesis and the expression of outer membrane proteins. These promoter inversions are mediated by a single tyrosine recombinase encoded by BF2766 (orthologous to tsr19 in strain NCTC9343) in B. fragilis YCH46, which is located near IVp-I. A series of BF2766 mutants were constructed in which the two promoters were locked in different configurations (IVp-I/IVp-II = ON/ON, OFF/OFF, ON/OFF or OFF/ON). ON/ON B. fragilis mutants exhibited hypervesiculating, whereas the other mutants formed only a trace amount of OMVs. The hypervesiculating ON/ON mutants showed higher resistance to treatment with bile, LL-37, and human β-defensin 2. Incubation of wild-type cells with 5% bile increased the population of cells with the ON/ON genotype. These results indicate that B. fragilis regulates the formation of OMVs through DNA inversions at two distantly related promoter regions in response to membrane stress, although the mechanism underlying the interplay between the two regions controlled by the invertible promoters remains unknown.
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Affiliation(s)
- Haruyuki Nakayama-Imaohji
- Department of Microbiology, Faculty of Medicine, Kagawa University, 1750–1 Miki, Kagawa 761–0793, Japan
| | - Katsuhiko Hirota
- Department of Oral Microbiology, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima 770–8503, Japan
| | - Hisashi Yamasaki
- Department of Cellular and Molecular Medicine, Wakayama Medical University Graduate School of Medicine, Wakayama 641–8509, Japan
| | - Saori Yoneda
- Department of Microbiology, Faculty of Medicine, Kagawa University, 1750–1 Miki, Kagawa 761–0793, Japan
| | - Hirofumi Nariya
- Department of Microbiology, Faculty of Medicine, Kagawa University, 1750–1 Miki, Kagawa 761–0793, Japan
| | - Motoo Suzuki
- Department of Microbiology, Faculty of Medicine, Kagawa University, 1750–1 Miki, Kagawa 761–0793, Japan
| | - Thomas Secher
- Inserm UMR1043 Toulouse, France
- INRA USC 1360 Toulouse, France
- CNRS UMR5282 Toulouse, France
- Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France
| | - Yoichiro Miyake
- Department of Oral Microbiology, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima 770–8503, Japan
| | - Eric Oswald
- Inserm UMR1043 Toulouse, France
- INRA USC 1360 Toulouse, France
- CNRS UMR5282 Toulouse, France
- Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France
- CHU Toulouse, Hôpital Purpan, Service de bactériologie-hygiène, Toulouse, France
| | - Tetsuya Hayashi
- Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812–8582, Japan
| | - Tomomi Kuwahara
- Department of Microbiology, Faculty of Medicine, Kagawa University, 1750–1 Miki, Kagawa 761–0793, Japan
- * E-mail:
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Aoudia N, Rieu A, Briandet R, Deschamps J, Chluba J, Jego G, Garrido C, Guzzo J. Biofilms of Lactobacillus plantarum and Lactobacillus fermentum: Effect on stress responses, antagonistic effects on pathogen growth and immunomodulatory properties. Food Microbiol 2016; 53:51-9. [DOI: 10.1016/j.fm.2015.04.009] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 03/24/2015] [Accepted: 04/10/2015] [Indexed: 12/16/2022]
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Ganjali Dashti M, Abdeshahian P, Sudesh K, Phua KK. Optimization of Salmonella Typhi biofilm assay on polypropylene microtiter plates using response surface methodology. BIOFOULING 2016; 32:477-487. [PMID: 26963754 DOI: 10.1080/08927014.2015.1135328] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The objective of this study was to develop an optimized assay for Salmonella Typhi biofilm that mimics the environment of the gallbladder as an experimental model for chronic typhoid fever. Multi-factorial assays are difficult to optimize using traditional one-factor-at-a-time optimization methods. Response surface methodology (RSM) was used to optimize six key variables involved in S. Typhi biofilm formation on cholesterol-coated polypropylene 96-well microtiter plates. The results showed that bile (1.22%), glucose (2%), cholesterol (0.05%) and potassium chloride (0.25%) were critical factors affecting the amount of biofilm produced, but agitation (275 rpm) and sodium chloride (0.5%) had antagonistic effects on each other. Under these optimum conditions the maximum OD reading for biofilm formation was 3.4 (λ600 nm), and the coefficients of variation for intra-plate and inter-plate assays were 3% (n = 20) and 5% (n = 8), respectively. These results showed that RSM is an effective approach for biofilm assay optimization.
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Affiliation(s)
- M Ganjali Dashti
- a Ecobiomaterial Research Laboratory, School of Biological Sciences , Universiti Sains Malaysia , Penang , Malaysia
- b Enteric Diseases Research Cluster, Institute for Research in Molecular Medicine (INFORMM) , Universiti Sains Malaysia , Penang , Malaysia
| | - P Abdeshahian
- c Department of Bioprocess Engineering, Faculty of Chemical Engineering , Universiti Teknologi Malaysia, UTM , Skudai , Johor , Malaysia
| | - K Sudesh
- a Ecobiomaterial Research Laboratory, School of Biological Sciences , Universiti Sains Malaysia , Penang , Malaysia
| | - K K Phua
- b Enteric Diseases Research Cluster, Institute for Research in Molecular Medicine (INFORMM) , Universiti Sains Malaysia , Penang , Malaysia
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Hay AJ, Zhu J. In Sickness and in Health: The Relationships Between Bacteria and Bile in the Human Gut. ADVANCES IN APPLIED MICROBIOLOGY 2016; 96:43-64. [PMID: 27565580 DOI: 10.1016/bs.aambs.2016.07.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Colonization of a human host with a commensal microbiota has a complex interaction in which bacterial communities provide numerous health benefits to the host. An equilibrium between host and microbiota is kept in check with the help of biliary secretions by the host. Bile, composed primarily of bile salts, promotes digestion. It also provides a barrier between host and bacteria. After bile salts are synthesized in the liver, they are stored in the gallbladder to be released after food intake. The set of host-secreted bile salts is modified by the resident bacteria. Because bile salts are toxic to bacteria, an equilibrium of modified bile salts is reached that allows commensal bacteria to survive, yet rebuffs invading pathogens. In addition to direct toxic effects on cells, bile salts maintain homeostasis as signaling molecules, tuning the immune system. To cause disease, gram-negative pathogenic bacteria have shared strategies to survive this harsh environment. Through exclusion of bile, efflux of bile, and repair of bile-induced damage, these pathogens can successfully disrupt and outcompete the microbiota to activate virulence factors.
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Affiliation(s)
- A J Hay
- University of Pennsylvania, Philadelphia, PA, United States
| | - J Zhu
- University of Pennsylvania, Philadelphia, PA, United States
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Bile salt tolerance of Lactococcus lactis is enhanced by expression of bile salt hydrolase thereby producing less bile acid in the cells. Biotechnol Lett 2015; 38:659-65. [DOI: 10.1007/s10529-015-2018-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 12/10/2015] [Indexed: 12/24/2022]
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56
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Slížová M, Nemcová R, Mad’ar M, Hadryová J, Gancarčíková S, Popper M, Pistl J. Analysis of biofilm formation by intestinal lactobacilli. Can J Microbiol 2015; 61:437-46. [DOI: 10.1139/cjm-2015-0007] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study, the biofilm-forming potential of intestinal Lactobacillus reuteri strains under different culture conditions was characterized by microtiter plate biofilm assays. Moreover, the spatial organization of exogenously applied L. reuteri L2/6 (a pig isolate) at specific locations in gastrointestinal tract of monoassociated mice was investigated by fluorescence in situ hybridization. We did not detect biofilm formation by tested strains in nutrient-rich de Man–Rogosa–Sharpe (MRS) medium. On the contrary, a highly positive biofilm formation was observed in medium with lower accessibility to the carbon sources and lack of salts. The results obtained confirmed the significant role of Tween 80 and the quantity and nature of the sugars in the growth medium in biofilm formation. The omission of Tween 80 in MRS medium favored the formation of biofilm. Abundant biofilm formation was detected in the presence of lactose, galactose, and glucose. However, a gradual increase in sugar concentration triggered a significant decrease in biofilm formation. In addition, conditions related to the gastrointestinal environment, such as low pH and the presence of bile and mucins, highly modulated biofilm production. This effect seems to be dependent on the specificity and properties of the medium used for cultivation. From the evidence provided by this study we conclude that the biofilm formation capacity of L. reuteri is strongly dependent on the environmental factors and culture medium used.
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Affiliation(s)
- Magdaléna Slížová
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
| | - Radomíra Nemcová
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
| | - Marián Mad’ar
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
| | - Jana Hadryová
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
| | - Soňa Gancarčíková
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
| | - Miroslav Popper
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
| | - Juraj Pistl
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
- Department of Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic
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Role of gut barrier function in the pathogenesis of nonalcoholic Fatty liver disease. Gastroenterol Res Pract 2015; 2015:287348. [PMID: 25945084 PMCID: PMC4402198 DOI: 10.1155/2015/287348] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 03/28/2015] [Indexed: 02/07/2023] Open
Abstract
Nonalcoholic fatty liver disease (NAFLD) is one of the most common forms of chronic liver disease, and its incidence is increasing year by year. Many efforts have been made to investigate the pathogenesis of this disease. Since 1998 when Marshall proposed the conception of "gut-liver axis," more and more researchers have paid close attention to the role of gut barrier function in the pathogenesis of NAFLD. The four aspects of gut barrier function, including physical, chemical, biological, and immunological barriers, are interrelated closely and related to NAFLD. In this paper, we present a summary of research findings on the relationship between gut barrier dysfunction and the development of NAFLD, aiming at illustrating the role of gut barrier function in the pathogenesis of this disease.
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58
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Li XZ, Plésiat P, Nikaido H. The challenge of efflux-mediated antibiotic resistance in Gram-negative bacteria. Clin Microbiol Rev 2015; 28:337-418. [PMID: 25788514 PMCID: PMC4402952 DOI: 10.1128/cmr.00117-14] [Citation(s) in RCA: 1016] [Impact Index Per Article: 101.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The global emergence of multidrug-resistant Gram-negative bacteria is a growing threat to antibiotic therapy. The chromosomally encoded drug efflux mechanisms that are ubiquitous in these bacteria greatly contribute to antibiotic resistance and present a major challenge for antibiotic development. Multidrug pumps, particularly those represented by the clinically relevant AcrAB-TolC and Mex pumps of the resistance-nodulation-division (RND) superfamily, not only mediate intrinsic and acquired multidrug resistance (MDR) but also are involved in other functions, including the bacterial stress response and pathogenicity. Additionally, efflux pumps interact synergistically with other resistance mechanisms (e.g., with the outer membrane permeability barrier) to increase resistance levels. Since the discovery of RND pumps in the early 1990s, remarkable scientific and technological advances have allowed for an in-depth understanding of the structural and biochemical basis, substrate profiles, molecular regulation, and inhibition of MDR pumps. However, the development of clinically useful efflux pump inhibitors and/or new antibiotics that can bypass pump effects continues to be a challenge. Plasmid-borne efflux pump genes (including those for RND pumps) have increasingly been identified. This article highlights the recent progress obtained for organisms of clinical significance, together with methodological considerations for the characterization of MDR pumps.
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Affiliation(s)
- Xian-Zhi Li
- Human Safety Division, Veterinary Drugs Directorate, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada
| | - Patrick Plésiat
- Laboratoire de Bactériologie, Faculté de Médecine-Pharmacie, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon, France
| | - Hiroshi Nikaido
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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Kwan BW, Lord DM, Peti W, Page R, Benedik MJ, Wood TK. The MqsR/MqsA toxin/antitoxin system protects Escherichia coli during bile acid stress. Environ Microbiol 2015; 17:3168-81. [PMID: 25534751 DOI: 10.1111/1462-2920.12749] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 12/11/2014] [Indexed: 02/03/2023]
Abstract
Toxin/antitoxin (TA) systems are ubiquitous within bacterial genomes, and the mechanisms of many TA systems are well characterized. As such, several roles for TA systems have been proposed, such as phage inhibition, gene regulation and persister cell formation. However, the significance of these roles is nebulous due to the subtle influence from individual TA systems. For example, a single TA system has only a minor contribution to persister cell formation. Hence, there is a lack of defining physiological roles for individual TA systems. In this study, phenotype assays were used to determine that the MqsR/MqsA type II TA system of Escherichia coli is important for cell growth and tolerance during stress from the bile salt deoxycholate. Using transcriptomics and purified MqsR, we determined that endoribonuclease toxin MqsR degrades YgiS mRNA, which encodes a periplasmic protein that promotes deoxycholate uptake and reduces tolerance to deoxycholate exposure. The importance of reducing YgiS mRNA by MqsR is evidenced by improved growth, reduced cell death and reduced membrane damage when cells without ygiS are stressed with deoxycholate. Therefore, we propose that MqsR/MqsA is physiologically important for E. coli to thrive in the gallbladder and upper intestinal tract, where high bile concentrations are prominent.
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Affiliation(s)
- Brian W Kwan
- Department of Chemical Engineering, Pennsylvania State University, University Park, PA, 16802-4400, USA
| | - Dana M Lord
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI, 02912, USA
| | - Wolfgang Peti
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI, 02912, USA.,Department of Chemistry, Brown University, Providence, RI, 02912, USA
| | - Rebecca Page
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, 02912, USA
| | - Michael J Benedik
- Department of Biology, Texas A & M University, College Station, TX, 77845, USA
| | - Thomas K Wood
- Department of Chemical Engineering, Pennsylvania State University, University Park, PA, 16802-4400, USA.,Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, 16802-4400, USA
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Vuotto C, Donelli G. Anaerobes in Biofilm-Based Healthcare-Associated Infections. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 830:97-112. [DOI: 10.1007/978-3-319-11038-7_6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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The role of pgaC in Klebsiella pneumoniae virulence and biofilm formation. Microb Pathog 2014; 77:89-99. [PMID: 25450884 DOI: 10.1016/j.micpath.2014.11.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 09/19/2014] [Accepted: 11/05/2014] [Indexed: 11/23/2022]
Abstract
BACKGROUND Klebsiella pneumoniae has emerged as one of the major pathogens for community-acquired and nosocomial infections. A four-gene locus that had a high degree similarity with Escherichia coli pgaABCD and Yersinia pestis hmsHFRS was identified in K. pneumoniae genomes. The pgaABCD in E. coli encodes the envelope-spanning Pga machinery for the synthesis and secretion of poly-β-linked N-acetylglucosamine (PNAG). In a limited number of phylogenetically diverse bacteria, PNAG was demonstrated to mediate biofilm formation and had a role in the host-bacteria interactions. The presence of conserved pgaABCD locus among various K. pneumoniae strains suggested a putative requirement of PNAG for this bacterium. RESULTS In this study, an in-frame deletion of pgaC was generated in K. pneumoniae CG43 and named ΔpgaC. The loss of pgaC affected the production of PNAG and attenuated the enhancement of in vitro biofilm formation upon the addition of bile salts mixture. In mouse models, ΔpgaC exhibited a weakened ability to colonize the intestine, to disseminate extraintestinally, and to induce a systemic infection when compared to K. pneumoniae CG43. CONCLUSIONS Our study demonstrated that pgaC participated in the bile salts induced biofilm formation and was required for K. pneumoniae virulence in vivo.
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Silva JO, Martins Reis AC, Quesada-Gómez C, Pinheiro AQ, Freire RS, Oriá RB, de Carvalho CBM. In vitro effect of antibiotics on biofilm formation by Bacteroides fragilis group strains isolated from intestinal microbiota of dogs and their antimicrobial susceptibility. Anaerobe 2014; 28:24-8. [DOI: 10.1016/j.anaerobe.2014.04.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Revised: 04/17/2014] [Accepted: 04/18/2014] [Indexed: 10/25/2022]
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Ambalam P, Kondepudi KK, Nilsson I, Wadström T, Ljungh Å. Bile Enhances Cell Surface Hydrophobicity and Biofilm Formation of Bifidobacteria. Appl Biochem Biotechnol 2013; 172:1970-81. [DOI: 10.1007/s12010-013-0596-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 10/07/2013] [Indexed: 01/24/2023]
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The ABC-type efflux pump MacAB protects Salmonella enterica serovar typhimurium from oxidative stress. mBio 2013; 4:e00630-13. [PMID: 24169575 PMCID: PMC3809562 DOI: 10.1128/mbio.00630-13] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Multidrug efflux pumps are integral membrane proteins known to actively excrete antibiotics. The macrolide-specific pump MacAB, the only ABC-type drug efflux pump in Salmonella, has previously been linked to virulence in mice. The molecular mechanism of this link between macAB and infection is unclear. We demonstrate that macAB plays a role in the detoxification of reactive oxygen species (ROS), compounds that salmonellae are exposed to at various stages of infection. macAB is induced upon exposure to H2O2 and is critical for survival of Salmonella enterica serovar Typhimurium in the presence of peroxide. Furthermore, we determined that macAB is required for intracellular replication inside J774.A1 murine macrophages but is not required for survival in ROS-deficient J774.D9 macrophages. macAB mutants also had reduced survival in the intestine in the mouse colitis model, a model characterized by a strong neutrophilic intestinal infiltrate where bacteria may experience the cytotoxic actions of ROS. Using an Amplex red-coupled assay, macAB mutants appear to be unable to induce protection against exogenous H2O2in vitro, in contrast to the isogenic wild type. In mixed cultures, the presence of the wild-type organism, or media preconditioned by the growth of the wild-type organism, was sufficient to rescue the macAB mutant from peroxide-mediated killing. Our data indicate that the MacAB drug efflux pump has functions beyond resistance to antibiotics and plays a role in the protection of Salmonella against oxidative stress. Intriguingly, our data also suggest the presence of a soluble anti-H2O2 compound secreted by Salmonella cells through a MacAB-dependent mechanism. The ABC-type multidrug efflux pump MacAB is known to be required for Salmonella enterica serovar Typhimurium virulence after oral infection in mice, yet the function of this pump during infection is unknown. We show that this pump is necessary for colonization of niches in infected mice where salmonellae encounter oxidative stress during infection. MacAB is required for growth in cultured macrophages that produce reactive oxygen species (ROS) but is not needed in macrophages that do not generate ROS. In addition, we show that MacAB is required to resist peroxide-mediated killing in vitro and for the inactivation of peroxide in the media. Finally, wild-type organisms, or supernatant from wild-type organisms grown in the presence of peroxide, rescue the growth defect of macAB mutants in H2O2. MacAB appears to participate in the excretion of a compound that induces protection against ROS-mediated killing, revealing a new role for this multidrug efflux pump.
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Ferreira EDO, Teixeira FL, Cordeiro F, Araujo Lobo L, Rocha ER, Smith JC, Domingues RMCP. The Bfp60 surface adhesin is an extracellular matrix and plasminogen protein interacting in Bacteroides fragilis. Int J Med Microbiol 2013; 303:492-7. [PMID: 23850366 DOI: 10.1016/j.ijmm.2013.06.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 05/12/2013] [Accepted: 06/16/2013] [Indexed: 01/05/2023] Open
Abstract
Plasminogen (Plg) is a highly abundant protein found in the plasma component of blood and is necessary for the degradation of fibrin, collagen, and other structural components of tissues. This fibrinolytic system is utilized by several pathogenic species of bacteria to manipulate the host plasminogen system and facilitate invasion of tissues during infection by modifying the activation of this process through the binding of Plg at their surface. Bacteroides fragilis is the most commonly isolated Gram-negative obligate anaerobe from human clinical infections, such as intra-abdominal abscesses and anaerobic bacteraemia. The ability of B. fragilis to convert plasminogen (Plg) into plasmin has been associated with an outer membrane protein named Bfp60. In this study, we characterized the function of Bfp60 protein in B. fragilis 638R by constructing the bfp60 defective strain and comparing its with that of the wild type regarding binding to laminin-1 (LMN-1) and activation of Plg into plasmin. Although the results showed in this study indicate that Bfp60 surface protein of B. fragilis is important for the recognition of LMN-1 and Plg activation, a significant slow activation of Plg into plasmin was observed in the mutant strain. For that reason, the possibility of another unidentified mechanism activating Plg is also present in B. fragilis cannot be discarded. The results demonstrate that Bfp60 protein is responsible for the recognition of laminin and Plg-plasmin activation. Although the importance of this protein is still unclear in the pathogenicity of the species, it is accepted that since other pathogenic bacteria use this mechanism to disseminate through the extracellular matrix during the infection, it should also contribute to the virulence of B. fragilis.
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Affiliation(s)
- Eliane de Oliveira Ferreira
- Laboratório de Biologia de Anaeróbios, Departamento de Microbiologia Médica, UFRJ, Ilha do Fundão, CCS, Instituto de Microbiologia Prof. Paulo de Góes, Rio de Janeiro, Brazil; Universidade Federal do Rio de Janeiro - Polo Xerém, Estrada de Xerém, 27, Duque de Caxias, Rio de Janeiro, CEP: 25245-390, Brazil.
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Effect of Bacteriocins and Conditions that Mimic Food and Digestive Tract on Biofilm Formation, In Vitro Invasion of Eukaryotic Cells and Internalin Gene Expression by Listeria monocytogenes. Probiotics Antimicrob Proteins 2013; 5:153-64. [DOI: 10.1007/s12602-013-9135-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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67
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Barnett Foster D. Modulation of the enterohemorrhagic E. coli virulence program through the human gastrointestinal tract. Virulence 2013; 4:315-23. [PMID: 23552827 PMCID: PMC3710334 DOI: 10.4161/viru.24318] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Enteric pathogens must not only survive passage through the gastrointestinal tract but must also coordinate expression of virulence determinants in response to localized microenvironments with the host. Enterohemorrhagic Escherichia coli (EHEC), a serious food and waterborne human pathogen, is well equipped with an arsenal of molecular factors that allows it to survive passage through the gastrointestinal tract and successfully colonize the large intestine. This review will explore how EHEC responds to various environmental cues associated with particular microenvironments within the host and how it employs these cues to modulate virulence factor expression, with a view to developing a conceptual framework for understanding modulation of EHEC’s virulence program in response to the host. In vitro studies offer significant insights into the role of individual environmental cues but in vivo studies using animal models as well as data from natural infections will ultimately provide a more comprehensive picture of the highly regulated virulence program of this pathogen.
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Affiliation(s)
- Debora Barnett Foster
- Department of Chemistry and Biology, Faculty of Science, Ryerson University, Toronto, ONT, Canada.
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Alvarez-Ortega C, Olivares J, Martínez JL. RND multidrug efflux pumps: what are they good for? Front Microbiol 2013; 4:7. [PMID: 23386844 PMCID: PMC3564043 DOI: 10.3389/fmicb.2013.00007] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 01/07/2013] [Indexed: 01/27/2023] Open
Abstract
Multidrug efflux pumps are chromosomally encoded genetic elements capable of mediating resistance to toxic compounds in several life forms. In bacteria, these elements are involved in intrinsic and acquired resistance to antibiotics. Unlike other well-known horizontally acquired antibiotic resistance determinants, genes encoding for multidrug efflux pumps belong to the core of bacterial genomes and thus have evolved over millions of years. The selective pressure stemming from the use of antibiotics to treat bacterial infections is relatively recent in evolutionary terms. Therefore, it is unlikely that these elements have evolved in response to antibiotics. In the last years, several studies have identified numerous functions for efflux pumps that go beyond antibiotic extrusion. In this review we present some examples of these functions that range from bacterial interactions with plant or animal hosts, to the detoxification of metabolic intermediates or the maintenance of cellular homeostasis.
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Affiliation(s)
- Carolina Alvarez-Ortega
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas Madrid, Spain
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69
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Thornton RF, Murphy EC, Kagawa TF, O'Toole PW, Cooney JC. The effect of environmental conditions on expression of Bacteroides fragilis and Bacteroides thetaiotaomicron C10 protease genes. BMC Microbiol 2012; 12:190. [PMID: 22943521 PMCID: PMC3462683 DOI: 10.1186/1471-2180-12-190] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Accepted: 08/23/2012] [Indexed: 01/07/2023] Open
Abstract
Background Bacteroides fragilis and Bacteroides thetaiotaomicron are members of the normal human intestinal microbiota. However, both organisms are capable of causing opportunistic infections, during which the environmental conditions to which the bacteria are exposed change dramatically. To further explore their potential for contributing to infection, we have characterized the expression in B. thetaiotaomicron of four homologues of the gene encoding the C10 cysteine protease SpeB, a potent extracellular virulence factor produced by Streptococcus pyogenes. Results We identified a paralogous set of genes (btp genes) in the B. thetaiotaomicron genome, that were related to C10 protease genes we recently identified in B. fragilis. Similar to C10 proteases found in B. fragilis, three of the B. thetaiotaomicron homologues were transcriptionally coupled to genes encoding small proteins that are similar in structural architecture to Staphostatins, protease inhibitors associated with Staphopains in Staphylococcus aureus. The expression of genes for these C10 proteases in both B. fragilis and B. thetaiotaomicron was found to be regulated by environmental stimuli, in particular by exposure to oxygen, which may be important for their contribution to the development of opportunistic infections. Conclusions Genes encoding C10 proteases are increasingly identified in operons which also contain genes encoding proteins homologous to protease inhibitors. The Bacteroides C10 protease gene expression levels are responsive to different environmental stimuli suggesting they may have distinct roles in the bacterial-host interaction.
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70
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Ambalam P, Kondepudi KK, Nilsson I, Wadström T, Ljungh Å. Bile stimulates cell surface hydrophobicity, Congo red binding and biofilm formation of Lactobacillus strains. FEMS Microbiol Lett 2012; 333:10-9. [PMID: 22563647 DOI: 10.1111/j.1574-6968.2012.02590.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Revised: 04/20/2012] [Accepted: 04/25/2012] [Indexed: 11/28/2022] Open
Abstract
Seventeen Lactobacillus strains were tested for cell surface hydrophobicity (CSH) using the salt aggregation test (SAT) and Congo red binding (CRB) assay. CRB was dependent on pH and ionic strength and was protease-sensitive. In the presence of 100 μg mL(-1) cholesterol, the CRB was significantly reduced. Autoaggregating (AA) Lactobacillus crispatus strains showed 50% more CRB than the reference strain, the curli-producing Escherichia coli MC4 100. CRB of L. crispatus 12005, L. paracasei F8, L. plantarum F44 and L. paracasei F19 were enhanced when grown in Man Rogosa Sharpe (MRS) broth with 0.5% taurocholic acid (TA) or 5% porcine bile (PB) (P < 0.05). CSH was also enhanced for the non-AA strains L. plantarum F44, L. paracasei F19 and L. rhamnosus GG when grown in MRS broth with 0.5% TA, 5% PB or 0.25% mucin, with enhanced biofilm formation in MRS broth with bile (P < 0.05). Two AA strains, L. crispatus 12005 and L. paracasei F8, developed biofilm independent of bile or mucin. In summary, under bile-stressed growth conditions, early (24-h cultures) biofilm formation is associated with an increase in hydrophobic cell surface proteins and high CRB. Late mature (72-h culture) biofilm contained more carbohydrates, as shown by crystal violet staining.
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Affiliation(s)
- Padma Ambalam
- Division of Bacteriology, Department of Clinical Microbiology, Lund University Hospital, Lund, Sweden
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71
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Donelli G, Vuotto C, Cardines R, Mastrantonio P. Biofilm-growing intestinal anaerobic bacteria. ACTA ACUST UNITED AC 2012; 65:318-25. [PMID: 22444687 DOI: 10.1111/j.1574-695x.2012.00962.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 03/01/2012] [Accepted: 03/12/2012] [Indexed: 02/06/2023]
Abstract
Sessile growth of anaerobic bacteria from the human intestinal tract has been poorly investigated, so far. We recently reported data on the close association existing between biliary stent clogging and polymicrobial biofilm development in its lumen. By exploiting the explanted stents as a rich source of anaerobic bacterial strains belonging to the genera Bacteroides, Clostridium, Fusobacterium, Finegoldia, Prevotella, and Veillonella, the present study focused on their ability to adhere, to grow in sessile mode and to form in vitro mono- or dual-species biofilms. Experiments on dual-species biofilm formation were planned on the basis of the anaerobic strains isolated from each clogged biliary stent, by selecting those in which a couple of anaerobic strains belonging to different species contributed to the polymicrobial biofilm development. Then, strains were investigated by field emission scanning electron microscopy and confocal laser scanning microscopy to reveal if they are able to grow as mono- and/or dual-species biofilms. As far as we know, this is the first report on the ability to adhere and form mono/dual-species biofilms exhibited by strains belonging to the species Bacteroides oralis, Clostridium difficile, Clostridium baratii, Clostridium fallax, Clostridium bifermentans, Finegoldia magna, and Fusobacterium necrophorum.
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Affiliation(s)
- Gianfranco Donelli
- Microbial Biofilm Laboratory, IRCCS Fondazione Santa Lucia, Rome, Italy.
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72
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Dai X, Lv ZS. Role of gut barrier function in the pathogenesis of nonalcoholic fatty liver disease. Shijie Huaren Xiaohua Zazhi 2012; 20:656-661. [DOI: 10.11569/wcjd.v20.i8.656] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Nonalcoholic fatty liver disease (NAFLD) is one of the most common forms of chronic liver disease, and its incidence is increasing year by year. Many efforts have been made to investigate the pathogenesis of this disease. Since 1998 when Marshall proposed the conception of "gut-liver axis", more and more researchers have paid close attention to the role of gut barrier function in the pathogenesis of NAFLD. The four aspects of gut barrier function, including physical, chemical, biological and immunological barriers are interrelated closely and related to NAFLD. In this paper, we present a summary of research findings on the relationship between gut barrier dysfunction and the occurrence and development of NAFLD, aiming at illustrating the role of gut barrier function in the pathogenesis of this disease.
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Biofilm lifestyle enhances diesel bioremediation and biosurfactant production in the Antarctic polyhydroxyalkanoate producer Pseudomonas extremaustralis. Biodegradation 2012; 23:645-51. [DOI: 10.1007/s10532-012-9540-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Accepted: 01/20/2012] [Indexed: 10/14/2022]
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74
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Wexler HM. Pump it up: occurrence and regulation of multi-drug efflux pumps in Bacteroides fragilis. Anaerobe 2012; 18:200-8. [PMID: 22266580 DOI: 10.1016/j.anaerobe.2011.12.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 12/12/2011] [Accepted: 12/13/2011] [Indexed: 11/25/2022]
Abstract
Bacteroides fragilis is a gram-negative anaerobic commensal that can be a virulent pathogen when it escapes its normal niche in the human gut. Recent increases in reports of multi-drug resistance strains of this organism have lent urgency to understanding its mechanisms of antimicrobial resistance. We have identified and characterized RND-type multi-drug efflux pumps in B. fragilis which can pump out a variety of substrates and whose transcription levels can be elevated by a wide variety of antimicrobials, antiseptic agents, bile and other stressors. Our research is directed toward understanding how the efflux pump genes are controlled and how we may exploit that understanding to develop more effective, targeted therapy that will cure the infection without disrupting the entire gut microbiome that is so important in many aspects of human health.
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Affiliation(s)
- Hannah M Wexler
- GLAVAHCS, UCLA Department of Medicine, Los Angeles, CA 90073, USA.
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75
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Analysis of global transcriptional profiles of enterotoxigenic Escherichia coli isolate E24377A. Infect Immun 2012; 80:1232-42. [PMID: 22215741 DOI: 10.1128/iai.06138-11] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is an important pathogenic variant (pathovar) of E. coli in developing countries from a human health perspective, causing significant morbidity and mortality. Previous studies have examined specific regulatory networks in ETEC, although little is known about the global effects of inter- and intrakingdom signaling on the expression of virulence and colonization factors in ETEC. In this study, an E. coli/Shigella pan-genome microarray, combined with quantitative reverse transcriptase PCR (qRT-PCR) and RNA sequencing (RNA-seq), was used to quantify the expression of ETEC virulence and colonization factors. Biologically relevant chemical signals were combined with ETEC isolate E24377A during growth in either Luria broth (LB) or Dulbecco's modified Eagle medium (DMEM), and transcription was examined during different phases of the growth cycle; chemical signals examined included glucose, bile salts, and preconditioned media from E. coli/Shigella isolates. The results demonstrate that the presence of bile salts, which are found in the intestine and thought to be bactericidal, upregulates the expression of many ETEC virulence factors, including heat-stable (estA) and heat-labile (eltA) enterotoxin genes. In contrast, the ETEC colonization factors CS1 and CS3 were downregulated in the presence of bile, consistent with findings in studies of other enteric pathogens. RNA-seq analysis demonstrated that one of the most differentially expressed genes in the presence of bile is a unique plasmid-encoded AraC-like transcriptional regulator (peaR); other previously unknown genetic elements were found as well. These results provide transcriptional targets and putative mechanisms that should help improve understanding of the global regulatory networks and virulence expression in this important human pathogen.
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76
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Dowd SE, Wolcott RD, Kennedy J, Jones C, Cox SB. Molecular diagnostics and personalised medicine in wound care: assessment of outcomes. J Wound Care 2011; 20:232, 234-9. [PMID: 21647068 DOI: 10.12968/jowc.2011.20.5.232] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
OBJECTIVE This large, level A, retrospective cohort study set out to compare healing outcomes in three large cohorts of wound patients managed universally for bioburden: standard of care group, who were prescribed systemic antibiotics on the basis of empiric and traditional culture-based methodologies; treatment group 1, who were prescribed an improved selection of systemic antibiotics based on the results of molecular diagnostics; treatment group 2 who received personalised topical therapeutics (including antibiotics) based on the results of molecular diagnostics. METHOD Apart from the differences in diagnostic methods and antibiotic treatments described above, all three cohorts were subjected to the same biofilm-based wound care protocol, which included evaluation of the host and bioburden, frequent sharp debridement, use of wound dressings and comprehensive standard care (reperfusion therapy, nutritional support, offloading, compression and management of comorbidities). RESULTS In all, 1378 patients were recruited into the study. In the standard of care group 48.5% of patients (244/503) healed completely during the 7-month study period. This increased to 62.4% (298/479) in treatment group 1 and 90.4% (358/396) in treatment group 2. Cox proportional hazards analysis revealed the time to complete closure decreased by 26% in treatment group 1 (p<0.001) and 45.9% in treatment group 2 (p<0.001) compared with the standard of care group. Patients in treatment group 2 had >200% better odds of healing at any given time point compared with the other cohorts. CONCLUSION Implementation of personalised topical therapeutics guided by molecular diagnosis resulted in statistically and clinically significant improvements in outcome. The integration of molecular diagnostics and personalised medicine provides a directed and targeted approach to wound care. CONFLICT OF INTEREST SED and RDW are owners of PathoGenius Laboratories, a clinical diagnostic laboratory. SED and RDW are owners of Research and Testing Laboratory, which develops molecular diagnostics. CJ and JK are clinical advisors for PathoGenius. CJ and JK are owners of Southeastern Medical Compounding, Savannah, GA and Southeastern Medical Technologies, Savannah, GA.
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Affiliation(s)
- S E Dowd
- Research and Testing Laboratory and Pathogenius Diagnostics, Lubbock, TX, USA.
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77
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Bile salts induce resistance to polymyxin in enterohemorrhagic Escherichia coli O157:H7. J Bacteriol 2011; 193:4509-15. [PMID: 21725004 DOI: 10.1128/jb.00200-11] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many enteric bacteria use bile as an environmental cue to signal resistance and virulence gene expression. Microarray analysis of enterohemorrhagic Escherichia coli O157:H7 (EHEC) treated with bile salts revealed upregulation of genes for an efflux system (acrAB), a two-component signal transduction system (basRS/pmrAB), and lipid A modification (arnBCADTEF and ugd). Bile salt treatment of EHEC produced a basS- and arnT-dependent resistance to polymyxin.
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78
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Volynets V, Spruss A, Kanuri G, Wagnerberger S, Bischoff SC, Bergheim I. Protective effect of bile acids on the onset of fructose-induced hepatic steatosis in mice. J Lipid Res 2010; 51:3414-24. [PMID: 20847296 DOI: 10.1194/jlr.m007179] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Fructose intake is being discussed as a key dietary factor in the development of nonalcoholic fatty liver disease (NAFLD). Bile acids have been shown to modulate energy metabolism. We tested the effects of bile acids on fructose-induced hepatic steatosis. In C57BL/6J mice treated with a combination of chenodeoxycholic acid and cholic acid (100 mg/kg body weight each) while drinking water or a 30% fructose solution for eight weeks and appropriate controls, markers of hepatic steatosis, portal endotoxin levels, and markers of hepatic lipogenesis were determined. In mice concomitantly treated with bile acids, the onset of fructose-induced hepatic steatosis was markedly attenuated compared to mice only fed fructose. The protective effects of the bile acid treatment were associated with a downregulation of tumor necrosis factor (TNF)α, sterol regulatory element-binding protein (SREBP)1, FAS mRNA expression, and lipid peroxidation in the liver, whereas hepatic farnesoid X receptor (FXR) or short heterodimer partner (SHP) protein concentration did not differ between groups fed fructose. Rather, bile acid treatment normalized occludin protein concentration in the duodenum, portal endotoxin levels, and markers of Kupffer cell activation to the level of water controls. Taken together, these data suggest that bile acids prevent fructose-induced hepatic steatosis in mice through mechanisms involving protection against the fructose-induced translocation of intestinal bacterial endotoxin.
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Affiliation(s)
- Valentina Volynets
- Department of Nutritional Medicine, University of Hohenheim, Stuttgart, Germany
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79
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Xiao XL, Li YJ, Qin YY, Yu YG, Wu H. A multipathogen selective enrichment broth for simultaneous growth of Salmonella spp., Vibrio parahaemolyticus, and Vibrio cholerae. J GEN APPL MICROBIOL 2010; 56:465-74. [DOI: 10.2323/jgam.56.465] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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80
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Coats SR, Jones JW, Do CT, Braham PH, Bainbridge BW, To TT, Goodlett DR, Ernst RK, Darveau RP. Human Toll-like receptor 4 responses to P. gingivalis are regulated by lipid A 1- and 4'-phosphatase activities. Cell Microbiol 2009; 11:1587-99. [PMID: 19552698 PMCID: PMC3074576 DOI: 10.1111/j.1462-5822.2009.01349.x] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Signal transduction following binding of lipopolysaccharide (LPS) to Toll-like receptor 4 (TLR4) is an essential aspect of host innate immune responses to infection by Gram-negative pathogens. Here, we describe a novel molecular mechanism used by a prevalent human bacterial pathogen to evade and subvert the human innate immune system. We show that the oral pathogen, Porphyromonas gingivalis, uses endogenous lipid A 1- and 4'-phosphatase activities to modify its LPS, creating immunologically silent, non-phosphorylated lipid A. This unique lipid A provides a highly effective mechanism employed by this bacterium to evade TLR4 sensing and to resist killing by cationic antimicrobial peptides. In addition, lipid A 1-phosphatase activity is suppressed by haemin, an important nutrient in the oral cavity. Specifically, P. gingivalis grown in the presence of high haemin produces lipid A that acts as a potent TLR4 antagonist. These results suggest that haemin-dependent regulation of lipid A 1-dephosphorylation can shift P. gingivalis lipid A activity from TLR4 evasive to TLR4 suppressive, potentially altering critical interactions between this bacterium, the local microbial community and the host innate immune system.
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Affiliation(s)
- Stephen R Coats
- Department of Periodontics, School of Dentistry, University of Washington, 1959 NE Pacific St., Seattle, WA 98195-7444, USA.
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81
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Abstract
Drug efflux pumps play a key role in drug resistance and also serve other functions in bacteria. There has been a growing list of multidrug and drug-specific efflux pumps characterized from bacteria of human, animal, plant and environmental origins. These pumps are mostly encoded on the chromosome, although they can also be plasmid-encoded. A previous article in this journal provided a comprehensive review regarding efflux-mediated drug resistance in bacteria. In the past 5 years, significant progress has been achieved in further understanding of drug resistance-related efflux transporters and this review focuses on the latest studies in this field since 2003. This has been demonstrated in multiple aspects that include but are not limited to: further molecular and biochemical characterization of the known drug efflux pumps and identification of novel drug efflux pumps; structural elucidation of the transport mechanisms of drug transporters; regulatory mechanisms of drug efflux pumps; determining the role of the drug efflux pumps in other functions such as stress responses, virulence and cell communication; and development of efflux pump inhibitors. Overall, the multifaceted implications of drug efflux transporters warrant novel strategies to combat multidrug resistance in bacteria.
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Affiliation(s)
- Xian-Zhi Li
- Human Safety Division, Veterinary Drugs Directorate, Health Products and Food Branch, Health Canada, Ottawa, Ontario K1A OK9, Canada
| | - Hiroshi Nikaido
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA
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82
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Begley M, Kerr C, Hill C. Exposure to bile influences biofilm formation by Listeria monocytogenes. Gut Pathog 2009; 1:11. [PMID: 19476630 PMCID: PMC2693109 DOI: 10.1186/1757-4749-1-11] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Accepted: 05/28/2009] [Indexed: 01/10/2023] Open
Abstract
In the present study we demonstrate that the initial attachment of Listeria monocytogenes cells to plastic surfaces was significantly increased by growth in the presence of bile. Improved biofilm formation was confirmed by crystal violet staining, microscopy and bioluminescence detection of a luciferase-tagged strain. Enhanced biofilm formation in response to bile may influence the ability of L. monocytogenes to form biofilms in vivo during infection and may contribute to survival of this important pathogen in the human gastrointestinal tract and gallbladder.
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Affiliation(s)
- Máire Begley
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland.
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83
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Gueimonde M, Garrigues C, van Sinderen D, de los Reyes-Gavilán CG, Margolles A. Bile-inducible efflux transporter from Bifidobacterium longum NCC2705, conferring bile resistance. Appl Environ Microbiol 2009; 75:3153-60. [PMID: 19304838 PMCID: PMC2681658 DOI: 10.1128/aem.00172-09] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Accepted: 03/10/2009] [Indexed: 12/28/2022] Open
Abstract
Bifidobacteria are normal inhabitants of the human gut. Some strains of this genus are considered health promoting or probiotic, being included in numerous food products. In order to exert their health benefits, these bacteria must overcome biological barriers, including bile salts, to colonize and survive in specific parts of the intestinal tract. The role of multidrug resistance (MDR) transporters in bile resistance of probiotic bacteria and the effect of bile on probiotic gene expression are not fully understood. In the present study, the effect of subinhibitory concentrations of bile on the expression levels of predicted MDR genes from three different bifidobacterial strains, belonging to Bifidobacterium longum subsp. longum, Bifidobacterium breve, and Bifidobacterium animalis subsp. lactis, was tested. In this way, two putative MDR genes whose expression was induced by bile, BL0920 from B. longum and its homolog, Bbr0838, from B. breve, were identified. The expression of the BL0920 gene in Escherichia coli was shown to confer resistance to bile, likely to be mediated by active efflux from the cells. To the best of our knowledge, this represents the first identified bifidobacterial bile efflux pump whose expression is induced by bile.
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Affiliation(s)
- Miguel Gueimonde
- Department of Microbiology and Biochemistry of Dairy Products, Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Villaviciosa, Asturias, Spain
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84
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Nickel promotes biofilm formation by Escherichia coli K-12 strains that produce curli. Appl Environ Microbiol 2009; 75:1723-33. [PMID: 19168650 DOI: 10.1128/aem.02171-08] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The survival of bacteria exposed to toxic compounds is a multifactorial phenomenon, involving well-known molecular mechanisms of resistance but also less-well-understood mechanisms of tolerance that need to be clarified. In particular, the contribution of biofilm formation to survival in the presence of toxic compounds, such as nickel, was investigated in this study. We found that a subinhibitory concentration of nickel leads Escherichia coli bacteria to change their lifestyle, developing biofilm structures rather than growing as free-floating cells. Interestingly, whereas nickel and magnesium both alter the global cell surface charge, only nickel promotes biofilm formation in our system. Genetic evidence indicates that biofilm formation induced by nickel is mediated by the transcriptional induction of the adhesive curli-encoding genes. Biofilm formation induced by nickel does not rely on efflux mechanisms using the RcnA pump, as these require a higher concentration of nickel to be activated. Our results demonstrate that the nickel-induced biofilm formation in E. coli is an adaptational process, occurring through a transcriptional effect on genes coding for adherence structures. The biofilm lifestyle is obviously a selective advantage in the presence of nickel, but the means by which it improves bacterial survival needs to be investigated.
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85
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Bile affects the synthesis of exopolysaccharides by Bifidobacterium animalis. Appl Environ Microbiol 2008; 75:1204-7. [PMID: 19088310 DOI: 10.1128/aem.00908-08] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
By using cryo-scanning electron microscopy and quantification with lectin-conjugated probes, we have detected the production of exopolysaccharides (EPS) in Bifidobacterium animalis subsp. lactis in the presence of bile. In addition, the expression of gtf01207, which codifies a putative priming glycosyltransferase involved in EPS synthesis, was induced by bile.
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86
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Sartor RB. Microbial influences in inflammatory bowel diseases. Gastroenterology 2008; 134:577-94. [PMID: 18242222 DOI: 10.1053/j.gastro.2007.11.059] [Citation(s) in RCA: 1371] [Impact Index Per Article: 80.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Accepted: 11/28/2007] [Indexed: 02/07/2023]
Abstract
The predominantly anaerobic microbiota of the distal ileum and colon contain an extraordinarily complex variety of metabolically active bacteria and fungi that intimately interact with the host's epithelial cells and mucosal immune system. Crohn's disease, ulcerative colitis, and pouchitis are the result of continuous microbial antigenic stimulation of pathogenic immune responses as a consequence of host genetic defects in mucosal barrier function, innate bacterial killing, or immunoregulation. Altered microbial composition and function in inflammatory bowel diseases result in increased immune stimulation, epithelial dysfunction, or enhanced mucosal permeability. Although traditional pathogens probably are not responsible for these disorders, increased virulence of commensal bacterial species, particularly Escherichia coli, enhance their mucosal attachment, invasion, and intracellular persistence, thereby stimulating pathogenic immune responses. Host genetic polymorphisms most likely interact with functional bacterial changes to stimulate aggressive immune responses that lead to chronic tissue injury. Identification of these host and microbial alterations in individual patients should lead to selective targeted interventions that correct underlying abnormalities and induce sustained and predictable therapeutic responses.
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Affiliation(s)
- R Balfour Sartor
- Department of Medicine, Center for Gastrointestinal Biology and Disease, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
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87
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Honma M, Sato Y, Kagiwada N, Kitamura M. Chronic superior mesenteric venous thrombosis revealed by diabetic ketonuria and bacteremia. Intern Med 2008; 47:1905-9. [PMID: 18981635 DOI: 10.2169/internalmedicine.47.1382] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
We report a patient with superior mesenteric venous thrombosis presenting as diabetic ketonuria and bacteremia. The patient was a 65-year-old man with a history of diabetes mellitus, and was admitted to our hospital due to high fever. Tests revealed diabetic ketonuria and Bacteroides fragilis bacteremia. Abdominal computed tomographic scan and Doppler sonography revealed an old thrombus in the superior mesenteric vein with good flow through collateral vessels, causing the patient to have an absence of abdominal symptoms. There was no evidence of hereditary thrombophilia. The thrombus was secondary to a combination of comorbidities, including dehydration, hyperosmolarity, and diabetes mellitus.
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Affiliation(s)
- Masashi Honma
- Division of Nephrology and Diabetes and Department of Internal Medicine, Tokai University Oiso Hospital, Kanagawa.
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88
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Abstract
SUMMARY Bacteroides species are significant clinical pathogens and are found in most anaerobic infections, with an associated mortality of more than 19%. The bacteria maintain a complex and generally beneficial relationship with the host when retained in the gut, but when they escape this environment they can cause significant pathology, including bacteremia and abscess formation in multiple body sites. Genomic and proteomic analyses have vastly added to our understanding of the manner in which Bacteroides species adapt to, and thrive in, the human gut. A few examples are (i) complex systems to sense and adapt to nutrient availability, (ii) multiple pump systems to expel toxic substances, and (iii) the ability to influence the host immune system so that it controls other (competing) pathogens. B. fragilis, which accounts for only 0.5% of the human colonic flora, is the most commonly isolated anaerobic pathogen due, in part, to its potent virulence factors. Species of the genus Bacteroides have the most antibiotic resistance mechanisms and the highest resistance rates of all anaerobic pathogens. Clinically, Bacteroides species have exhibited increasing resistance to many antibiotics, including cefoxitin, clindamycin, metronidazole, carbapenems, and fluoroquinolones (e.g., gatifloxacin, levofloxacin, and moxifloxacin).
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Lebeer S, Verhoeven TLA, Perea Vélez M, Vanderleyden J, De Keersmaecker SCJ. Impact of environmental and genetic factors on biofilm formation by the probiotic strain Lactobacillus rhamnosus GG. Appl Environ Microbiol 2007; 73:6768-75. [PMID: 17827316 PMCID: PMC2074970 DOI: 10.1128/aem.01393-07] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Lactobacillus rhamnosus GG (ATCC 53103) is one of the clinically best-studied probiotic organisms. Moreover, L. rhamnosus GG displays very good in vitro adherence to epithelial cells and mucus. Here, we report that L. rhamnosus GG is able to form biofilms on abiotic surfaces, in contrast to other strains of the Lactobacillus casei group tested under the same conditions. Microtiter plate biofilm assays indicated that in vitro biofilm formation by L. rhamnosus GG is strongly modulated by culture medium factors and conditions related to the gastrointestinal environment, including low pH; high osmolarity; and the presence of bile, mucins, and nondigestible polysaccharides. Additionally, phenotypic analysis of mutants affected in exopolysaccharides (wzb), lipoteichoic acid (dltD), and central metabolism (luxS) showed their relative importance in biofilm formation by L. rhamnosus GG.
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Affiliation(s)
- Sarah Lebeer
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, 3001 Leuven, Belgium
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