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Lu Y, Chen F, Zhao Q, Cao Q, Chen R, Pan H, Wang Y, Huang H, Huang R, Liu Q, Li M, Bae T, Liang H, Lan L. Modulation of MRSA virulence gene expression by the wall teichoic acid enzyme TarO. Nat Commun 2023; 14:1594. [PMID: 36949052 PMCID: PMC10032271 DOI: 10.1038/s41467-023-37310-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 03/10/2023] [Indexed: 03/24/2023] Open
Abstract
Phenol-soluble modulins (PSMs) and Staphylococcal protein A (SpA) are key virulence determinants for community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), an important human pathogen that causes a wide range of diseases. Here, using chemical and genetic approaches, we show that inhibition of TarO, the first enzyme in the wall teichoic acid (WTA) biosynthetic pathway, decreases the expression of genes encoding PSMs and SpA in the prototypical CA-MRSA strain USA300 LAC. Mechanistically, these effects are linked to the activation of VraRS two-component system that directly represses the expression of accessory gene regulator (agr) locus and spa. The activation of VraRS was due in part to the loss of the functional integrity of penicillin-binding protein 2 (PBP2) in a PBP2a-dependent manner. TarO inhibition can also activate VraRS in a manner independent of PBP2a. We provide multiple lines of evidence that accumulation of lipid-linked peptidoglycan precursors is a trigger for the activation of VraRS. In sum, our results reveal that WTA biosynthesis plays an important role in the regulation of virulence gene expression in CA-MRSA, underlining TarO as an attractive target for anti-virulence therapy. Our data also suggest that acquisition of PBP2a-encoding mecA gene can impart an additional regulatory layer for the modulation of key signaling pathways in S. aureus.
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Affiliation(s)
- Yunfu Lu
- School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, China
| | - Feifei Chen
- School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- College of Life Science, Northwest University, Xi'an, 710127, China
| | - Qingmin Zhao
- School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, China
| | - Qiao Cao
- School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- College of Life Science, Northwest University, Xi'an, 710127, China
| | - Rongrong Chen
- School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, China
| | - Huiwen Pan
- School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, China
| | - Yanhui Wang
- School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, China
| | - Haixin Huang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Ruimin Huang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, China
| | - Qian Liu
- Department of Laboratory Medicine, School of Medicine, Renji Hospital, Shanghai Jiao Tong University, Shanghai, 200127, China
| | - Min Li
- Department of Laboratory Medicine, School of Medicine, Renji Hospital, Shanghai Jiao Tong University, Shanghai, 200127, China
| | - Taeok Bae
- Department of Microbiology and Immunology, Indiana University School of Medicine-Northwest, Gary, IN, 46408, USA
| | - Haihua Liang
- College of Life Science, Northwest University, Xi'an, 710127, China.
- School of Medicine, Southern University of Science and Technology, Shenzhen, 518055, China.
| | - Lefu Lan
- School of Pharmaceutical Science and Technology, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China.
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.
- University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, China.
- College of Life Science, Northwest University, Xi'an, 710127, China.
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2
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Jahan S, Davis H, Ashcraft DS, Pankey GA. Evaluation of the in vitro interaction of fosfomycin and meropenem against metallo-β-lactamase-producing Pseudomonas aeruginosa using Etest and time-kill assay. J Investig Med 2020; 69:371-376. [PMID: 33122248 DOI: 10.1136/jim-2020-001573] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/07/2020] [Indexed: 11/04/2022]
Abstract
Pseudomonas aeruginosa is a nosocomial pathogen containing various resistance mechanisms. Among them, metallo-β-lactamase (MBL)-producing Pseudomonas are difficult to treat. Fosfomycin is an older antibiotic that has recently seen increased usage due to its activity against a broad spectrum of multidrug-resistant organisms. Our aim was to evaluate the combination of fosfomycin and meropenem against 20 MBL-producing P. aeruginosa (100% meropenem-resistant and 20% fosfomycin-resistant) using both an Etest minimal inhibitory concentration (MIC): MIC method and time-kill assay. MICs for fosfomycin and meropenem were determined by Etest and by broth microdilution method for the latter. The combination demonstrated synergy by Etest in 3/20 (15%) isolates and 5/20 (25%) isolates by time-kill assay. Results from the Etest method and time-kill assay were in agreement for 14/20 (70%) of isolates. No antagonism was found. Comparing both methods, Etest MIC: MIC method may be useful to rapidly evaluate other antimicrobial combinations.
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Affiliation(s)
- Sanjida Jahan
- Infectious Disease Translational Research, Ochsner Clinic Foundation, New Orleans, Louisiana, USA
| | - Heather Davis
- Infectious Disease Translational Research, Ochsner Clinic Foundation, New Orleans, Louisiana, USA
| | - Deborah S Ashcraft
- Infectious Disease Translational Research, Ochsner Clinic Foundation, New Orleans, Louisiana, USA
| | - George A Pankey
- Infectious Disease Translational Research, Ochsner Clinic Foundation, New Orleans, Louisiana, USA .,Infectious Disease Translational Research, Ochsner Clinic Foundation, New Orleans, Louisiana, USA
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Salas JR, Jaberi-Douraki M, Wen X, Volkova VV. Mathematical modeling of the 'inoculum effect': six applicable models and the MIC advancement point concept. FEMS Microbiol Lett 2020; 367:5710933. [PMID: 31960902 PMCID: PMC7317156 DOI: 10.1093/femsle/fnaa012] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 01/17/2020] [Indexed: 01/09/2023] Open
Abstract
Antimicrobial treatment regimens against bacterial pathogens are designed using the drug's minimum inhibitory concentration (MIC) measured at a bacterial density of 5.7 log10(colony-forming units (CFU)/mL) in vitro. However, MIC changes with pathogen density, which varies among infectious diseases and during treatment. Incorporating this into treatment design requires realistic mathematical models of the relationships. We compared the MIC–density relationships for Gram-negative Escherichia coli and non-typhoidal Salmonella enterica subsp. enterica and Gram-positive Staphylococcus aureus and Streptococcus pneumonia (for n = 4 drug-susceptible strains per (sub)species and 1–8 log10(CFU/mL) densities), for antimicrobial classes with bactericidal activity against the (sub)species: β-lactams (ceftriaxone and oxacillin), fluoroquinolones (ciprofloxacin), aminoglycosides (gentamicin), glycopeptides (vancomycin) and oxazolidinones (linezolid). Fitting six candidate mathematical models to the log2(MIC) vs. log10(CFU/mL) curves did not identify one model best capturing the relationships across the pathogen–antimicrobial combinations. Gompertz and logistic models (rather than a previously proposed Michaelis–Menten model) fitted best most often. Importantly, the bacterial density after which the MIC sharply increases (an MIC advancement-point density) and that density's intra-(sub)species range evidently depended on the antimicrobial mechanism of action. Capturing these dependencies for the disease–pathogen–antimicrobial combination could help determine the MICs for which bacterial densities are most informative for treatment regimen design.
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Affiliation(s)
- Jessica R Salas
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, KS 66506, USA
| | - Majid Jaberi-Douraki
- Department of Mathematics, Kansas State University, Manhattan, KS 66506, USA.,Institute of Computational Comparative Medicine, Department of Anatomy and Physiology, Kansas State University, Manhattan, KS 66506, USA
| | - Xuesong Wen
- Institute of Computational Comparative Medicine, Department of Anatomy and Physiology, Kansas State University, Manhattan, KS 66506, USA.,Department of Anatomy and Physiology, Kansas State University, Manhattan, KS 66506, USA
| | - Victoriya V Volkova
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, KS 66506, USA.,Center for Outcomes Research and Epidemiology, Kansas State University, Manhattan, KS 66506, USA
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Hasan I, Ozeki Y. Histochemical localization of N-acetylhexosamine-binding lectin HOL-18 in Halichondria okadai (Japanese black sponge), and its antimicrobial and cytotoxic anticancer effects. Int J Biol Macromol 2018; 124:819-827. [PMID: 30496858 DOI: 10.1016/j.ijbiomac.2018.11.222] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Revised: 11/25/2018] [Accepted: 11/25/2018] [Indexed: 10/27/2022]
Abstract
We studied localization and physiological activities of a lectin showing specific binding to N-acetylhexosamines, termed HOL-18, purified from Japanese black sponge (Halichondria okadai). Antiserum against the lectin was generated in rabbit and applied for immunohistochemical analyses. HOL-18 was expressed specifically around water pores and on spicules of sponge tissues. It showed strong binding to a variety of N-acetylhexosamines: N-acetyl D-glucosamine, N-acetyl D-galactosamine, N-acetyl mannosamine, N-acetyl muramic acid, and N-acetyl neuraminic acid. Hemagglutination induced by the lectin was inhibited by lipopolysaccharides and a peptidoglycan. HOL-18 inhibited growth of a gram-positive bacterium (Listeria monocytogenes), gram-negative bacteria (Escherichia coli, Shigella boydii, Pseudomonas aeruginosa), and a fungus (Aspergillus niger). It displayed anti-biofilm activity against P. aeruginosa. HOL-18 was internalized into conidiophores of A. niger, and displayed notable antifungal activity. Fluorescence microscopy revealed binding and incorporation of the lectin into human cancer cell lines HeLa, MCF-7, and T47D, but not Caco-2. HOL-18 displayed dose-dependent cytotoxic effects against HeLa, MCF-7, and T47D, with respective IC50 values 40, 52, and 63 μg/mL. In HeLa cells, it activated phosphorylation of MAPK pathway molecule (ERK1/2) and activated caspase-3 to trigger apoptosis. HOL-18 thus has the potential to upregulate metabolic pathways in higher animal cells through binding to N-acetylhexosamines.
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Affiliation(s)
- Imtiaj Hasan
- Laboratory of Glycobiology and Marine Biochemistry, Department of Life and Environmental System Science, Graduate School of NanoBiosciences, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama 236-0027, Japan; Department of Biochemistry and Molecular Biology, Faculty of Science, University of Rajshahi, Rajshahi 6205, Bangladesh.
| | - Yasuhiro Ozeki
- Laboratory of Glycobiology and Marine Biochemistry, Department of Life and Environmental System Science, Graduate School of NanoBiosciences, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama 236-0027, Japan.
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5
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Inferring within-host bottleneck size: A Bayesian approach. J Theor Biol 2017; 435:218-228. [PMID: 28919397 DOI: 10.1016/j.jtbi.2017.09.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Revised: 08/07/2017] [Accepted: 09/13/2017] [Indexed: 12/21/2022]
Abstract
Recent technical developments in microbiology have led to new discoveries on the within-host dynamics of bacterial infections in laboratory animals. In particular, they have highlighted the importance of stochastic bottlenecks at the onset of invasive disease. A number of approaches exist for bottleneck-size estimation with respect to within-host bacterial infections; however, some are more appropriate than others under certain circumstances. A Bayesian comparison of several approaches is made in terms of the availability of isogenic multitype bacteria (e.g., WITS), knowledge of post-bottleneck dynamics, and the suitability of dilution with monotype bacteria. A sampling approach to bottleneck-size estimation is also introduced. The results are summarised by a guiding flowchart, which we hope will promote the use of quantitative models in microbiology to refine the analysis of animal experiment data.
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Ali-Ahmad A, Fadel F, Sebban-Kreuzer C, Ba M, Pélissier GD, Bornet O, Guerlesquin F, Bourne Y, Bordi C, Vincent F. Structural and functional insights into the periplasmic detector domain of the GacS histidine kinase controlling biofilm formation in Pseudomonas aeruginosa. Sci Rep 2017; 7:11262. [PMID: 28900144 PMCID: PMC5595915 DOI: 10.1038/s41598-017-11361-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 08/17/2017] [Indexed: 11/15/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogenic bacterium responsible for both acute and chronic infections and has developed resistance mechanisms due to its ability to promote biofilm formation and evade host adaptive immune responses. Here, we investigate the functional role of the periplasmic detector domain (GacSPD) from the membrane-bound GacS histidine kinase, which is one of the key players for biofilm formation and coordination of bacterial lifestyles. A gacS mutant devoid of the periplasmic detector domain is severely defective in biofilm formation. Functional assays indicate that this effect is accompanied by concomitant changes in the expression of the two RsmY/Z small RNAs that control activation of GacA-regulated genes. The solution NMR structure of GacSPD reveals a distinct PDC/PAS α/β fold characterized by a three-stranded β-sheet flanked by α-helices and an atypical major loop. Point mutations in a putative ligand binding pocket lined by positively-charged residues originating primarily from the major loop impaired biofilm formation. These results demonstrate the functional role of GacSPD, evidence critical residues involved in GacS/GacA signal transduction system that regulates biofilm formation, and document the evolutionary diversity of the PDC/PAS domain fold in bacteria.
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Affiliation(s)
| | - Firas Fadel
- CNRS, Aix Marseille Univ, AFMB, Marseille, France
- LISM, IMM, Aix-Marseille Univ and CNRS, Marseille, 13402, France
| | | | - Moly Ba
- LISM, IMM, Aix-Marseille Univ and CNRS, Marseille, 13402, France
| | | | - Olivier Bornet
- LISM, IMM, Aix-Marseille Univ and CNRS, Marseille, 13402, France
| | | | - Yves Bourne
- CNRS, Aix Marseille Univ, AFMB, Marseille, France
| | - Christophe Bordi
- LISM, IMM, Aix-Marseille Univ and CNRS, Marseille, 13402, France.
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Yang Y, Ricke SC, Tellez G, Kwon YM. Quantitative Tracking of Salmonella Enteritidis Transmission Routes Using Barcode-Tagged Isogenic Strains in Chickens: Proof-of-Concept Study. Front Vet Sci 2017; 4:15. [PMID: 28261587 PMCID: PMC5306393 DOI: 10.3389/fvets.2017.00015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 01/30/2017] [Indexed: 11/13/2022] Open
Abstract
Salmonella is an important foodborne bacterial pathogen, however, a fundamental understanding on Salmonella transmission routes within a poultry flock remains unclear. In this study, a series of barcode-tagged strains were constructed by inserting six random nucleotides into a functionally neutral region on the chromosome of S. Enteritidis as a tool for quantitative tracking of Salmonella transmission in chickens. Six distinct barcode-tagged strains were used for infection or contamination at either low dose (103 CFUs; three strains) or high dose (105 CFUs; three strains) in three independent experiments (Experiment 1 oral gavage; Experiment 2 contaminated feed; Experiment 3 contaminated water). For all chick experiments, cecal and foot-wash samples were collected from a subset of the chickens at days 7 or/and 14, from which genomic DNA was extracted and used to amplify the barcode regions. After the resulting PCR amplicons were pooled and analyzed by MiSeq sequencing, a total of approximately 1.5 million reads containing the barcode sequences were analyzed to determine the relative frequency of every barcode-tagged strain in each sample. In Experiment 1, the high dose of oral infection was correlated with greater dominance of the strains in the ceca of the respective seeder chickens and also in the contact chickens yet at lesser degrees. When chicks were exposed to contaminated feed (Experiment 2) or water (Experiment 3), there were no clear patterns of the barcode-tagged strains in relation to the dosage, except that the strains introduced at low dose required a longer time to colonize the ceca with contaminated feed. Most foot-wash samples contained only one to three strains for the majority of the samples, suggesting potential existence of an unknown mechanism(s) for strain exclusion. These results demonstrated the proof of concept of using barcode tagged to investigate transmission dynamics of Salmonella in chickens in a quantitative manner.
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Affiliation(s)
- Yichao Yang
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, USA
| | - Steven C. Ricke
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, USA
- Department of Food Science, University of Arkansas, Fayetteville, AR, USA
- Center of Food Safety, University of Arkansas, Fayetteville, AR, USA
| | - Guillermo Tellez
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, USA
| | - Young Min Kwon
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, USA
- Cell and Molecular Biology Program, University of Arkansas, Fayetteville, AR, USA
- Center of Food Safety, University of Arkansas, Fayetteville, AR, USA
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Ruwandeepika HAD, Karunasagar I, Bossier P, Defoirdt T. Expression and Quorum Sensing Regulation of Type III Secretion System Genes of Vibrio harveyi during Infection of Gnotobiotic Brine Shrimp. PLoS One 2015; 10:e0143935. [PMID: 26636765 PMCID: PMC4670211 DOI: 10.1371/journal.pone.0143935] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 11/11/2015] [Indexed: 12/24/2022] Open
Abstract
Type III secretion systems enable pathogens to inject their virulence factors directly into the cytoplasm of the host cells. The type III secretion system of Vibrio harveyi, a major pathogen of aquatic organisms and a model species in quorum sensing studies, is repressed by the quorum sensing master regulator LuxR. In this study, we found that during infection of gnotobiotic brine shrimp larvae, the expression levels of three type III secretion operons in V. harveyi increased within the first 12h after challenge and decreased again thereafter. The in vivo expression levels were highest in a mutant with a quorum sensing system that is locked in low cell density configuration (minimal LuxR levels) and lowest in a mutant with a quorum sensing system that is locked in the high cell density configuration (maximal LuxR levels), which is consistent with repression of type III secretion by LuxR. Remarkably, in vivo expression levels of the type III secretion system genes were much (> 1000 fold) higher than the in vitro expression levels, indicating that (currently unknown) host factors significantly induce the type III secretion system. Given the fact that type III secretion is energy-consuming, repression by the quorum sensing master regulators might be a mechanism to save energy under conditions where it does not provide an advantage to the cells.
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Affiliation(s)
- H. A. Darshanee Ruwandeepika
- Department of Livestock Production, Faculty of Agricultural Sciences, Sabaragamuwa University of Sri Lanka, Belihuloya, Sri Lanka
- Centre for Science Education and Research, UNESCO MIRCEN for Medical and Marine Biotechnology, Nitte University, Mangalore, India
| | - Indrani Karunasagar
- Centre for Science Education and Research, UNESCO MIRCEN for Medical and Marine Biotechnology, Nitte University, Mangalore, India
| | - Peter Bossier
- Laboratory of Aquaculture & Artemia Reference Center, Ghent University, Ghent, Belgium
| | - Tom Defoirdt
- Laboratory of Aquaculture & Artemia Reference Center, Ghent University, Ghent, Belgium
- * E-mail:
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Lee SW, Shet UK, Park SW, Lim HP, Yun KD, Kang SS, Kim SE. Identification of Enterococcus faecalis antigens specifically expressed in vivo. Restor Dent Endod 2015; 40:306-11. [PMID: 26587417 PMCID: PMC4650527 DOI: 10.5395/rde.2015.40.4.306] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 08/10/2015] [Indexed: 01/05/2023] Open
Abstract
Objectives Molecular mechanism of the pathogenicity of Enterococcus faecalis (E. faecalis), a suspected endodontic pathogen, has not yet been adequately elucidated due to limited information on its virulence factors. Here we report the identification of in vivo expressed antigens of E. faecalis by using a novel immunoscreening technique called change-mediated antigen technology (CMAT) and an experimental animal model of endodontic infection. Materials and Methods Among 4,500 E. coli recombinant clones screened, 19 positive clones reacted reproducibly with hyperimmune sera obtained from rabbits immunized with E. faecalis cells isolated from an experimental endodontic infection. DNA sequences from 16 of these in vivo-induced (IVI) genes were determined. Results Identified protein antigens of E. faecalis included enzymes involved in housekeeping functions, copper resistance protein, putative outer membrane proteins, and proteins of unknown function. Conclusions In vivo expressed antigens of E. faecalis could be identified by using a novel immune-screening technique CMAT and an experimental animal model of endodontic infection. Detailed analysis of these IVI genes will lead to a better understanding of the molecular mechanisms involved in the endodontic infection of E. faecalis.
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Affiliation(s)
- Seok-Woo Lee
- Department of Dental Education, Dental Science Research Institute and BK21 Project, School of Dentistry, Gwangju, Korea. ; Department of Periodontology, Dental Science Research Institute and BK21 Project, School of Dentistry, Gwangju, Korea
| | - Uttom K Shet
- Department of Maxillofacial Surgery, Dental Science Research Institute and BK21 Project, School of Dentistry, Gwangju, Korea
| | - Sang-Won Park
- Department of Prosthodontics, Dental Science Research Institute and BK21 Project, School of Dentistry, Gwangju, Korea
| | - Hyun-Pil Lim
- Department of Prosthodontics, Dental Science Research Institute and BK21 Project, School of Dentistry, Gwangju, Korea
| | - Kwi-Dug Yun
- Department of Prosthodontics, Dental Science Research Institute and BK21 Project, School of Dentistry, Gwangju, Korea
| | - Seong Soo Kang
- Department of Veterinary Medicine, Chonnam National University, Gwangju, Korea
| | - Se Eun Kim
- Department of Veterinary Medicine, Chonnam National University, Gwangju, Korea
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10
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Le Roux F, Wegner KM, Baker-Austin C, Vezzulli L, Osorio CR, Amaro C, Ritchie JM, Defoirdt T, Destoumieux-Garzón D, Blokesch M, Mazel D, Jacq A, Cava F, Gram L, Wendling CC, Strauch E, Kirschner A, Huehn S. The emergence of Vibrio pathogens in Europe: ecology, evolution, and pathogenesis (Paris, 11-12th March 2015). Front Microbiol 2015; 6:830. [PMID: 26322036 PMCID: PMC4534830 DOI: 10.3389/fmicb.2015.00830] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 07/28/2015] [Indexed: 02/02/2023] Open
Abstract
Global change has caused a worldwide increase in reports of Vibrio-associated diseases with ecosystem-wide impacts on humans and marine animals. In Europe, higher prevalence of human infections followed regional climatic trends with outbreaks occurring during episodes of unusually warm weather. Similar patterns were also observed in Vibrio-associated diseases affecting marine organisms such as fish, bivalves and corals. Basic knowledge is still lacking on the ecology and evolutionary biology of these bacteria as well as on their virulence mechanisms. Current limitations in experimental systems to study infection and the lack of diagnostic tools still prevent a better understanding of Vibrio emergence. A major challenge is to foster cooperation between fundamental and applied research in order to investigate the consequences of pathogen emergence in natural Vibrio populations and answer federative questions that meet societal needs. Here we report the proceedings of the first European workshop dedicated to these specific goals of the Vibrio research community by connecting current knowledge to societal issues related to ocean health and food security.
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Affiliation(s)
- Frédérique Le Roux
- Unié Physiologie Fonctionnelle des Organismes Marins, Ifremer , Plouzané, France ; CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Sorbonne Universités, UPMC Paris 06 , Roscoff cedex, France
| | - K Mathias Wegner
- Coastal Ecology, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research , List, Germany
| | | | - Luigi Vezzulli
- Department of Earth, Environmental and Life Sciences, University of Genoa , Genoa, Italy
| | - Carlos R Osorio
- Departamento de Microbioloxía e Parasitoloxía, Instituto de Acuicultura, Universidade de Santiago de Compostela , Santiago de Compostela, Spain
| | - Carmen Amaro
- Estructura de Investigación Interdisciplinar en Biotecnología y Biomedicina, Department of Microbiology and Ecology, University of Valencia , Valencia, Spain
| | - Jennifer M Ritchie
- Faculty of Health and Medical Sciences, University of Surrey , Guildford, UK
| | - Tom Defoirdt
- UGent Aquaculture R&D Consortium, Ghent University , Ghent, Belgium
| | - Delphine Destoumieux-Garzón
- Interactions Hôtes-Pathogènes-Environnements, UMR 5244, CNRS, Ifremer, Université de Perpignan Via Domita, Université de Montpellier , Montpellier, France
| | - Melanie Blokesch
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne , Lausanne, Switzerland
| | - Didier Mazel
- Département Génomes et Génétique, CNRS UMR3525, Unité Plasticité du Génome Bactérien, Institut Pasteur , Paris, France
| | - Annick Jacq
- Institute for Integrative Biology of the Cell, CEA, CNRS, Université Paris-Sud , Orsay, France
| | - Felipe Cava
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University , Umeå, Sweden
| | - Lone Gram
- Department of Systems Biology, Technical University of Denmark , Kongens Lyngby, Denmark
| | | | - Eckhard Strauch
- Federal Institute for Risk Assessment, National Reference Laboratory for Monitoring Bacteriological Contamination of Bivalve Molluscs , Berlin, Germany
| | - Alexander Kirschner
- Institute for Hygiene and Applied Immunology, Medical University of Vienna , Vienna, Austria
| | - Stephan Huehn
- Institute of Food Hygiene, Free University Berlin , Berlin, Germany
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Alteri CJ, Himpsl SD, Mobley HLT. Preferential use of central metabolism in vivo reveals a nutritional basis for polymicrobial infection. PLoS Pathog 2015; 11:e1004601. [PMID: 25568946 PMCID: PMC4287612 DOI: 10.1371/journal.ppat.1004601] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Accepted: 12/04/2014] [Indexed: 12/04/2022] Open
Abstract
The human genitourinary tract is a common anatomical niche for polymicrobial infection and a leading site for the development of bacteremia and sepsis. Most uncomplicated, community-acquired urinary tract infections (UTI) are caused by Escherichia coli, while another bacterium, Proteus mirabilis, is more often associated with complicated UTI. Here, we report that uropathogenic E. coli and P. mirabilis have divergent requirements for specific central pathways in vivo despite colonizing and occupying the same host environment. Using mutants of specific central metabolism enzymes, we determined glycolysis mutants lacking pgi, tpiA, pfkA, or pykA all have fitness defects in vivo for P. mirabilis but do not affect colonization of E. coli during UTI. Similarly, the oxidative pentose phosphate pathway is required only for P. mirabilis in vivo. In contrast, gluconeogenesis is required only for E. coli fitness in vivo. The remarkable difference in central pathway utilization between E. coli and P. mirabilis during experimental UTI was also observed for TCA cycle mutants in sdhB, fumC, and frdA. The distinct in vivo requirements between these pathogens suggest E. coli and P. mirabilis are not direct competitors within host urinary tract nutritional niche. In support of this, we found that co-infection with E. coli and P. mirabilis wild-type strains enhanced bacterial colonization and persistence of both pathogens during UTI. Our results reveal that complementary utilization of central carbon metabolism facilitates polymicrobial disease and suggests microbial activity in vivo alters the host urinary tract nutritional niche. The human urinary tract is a leading source for polymicrobial infections and for the development of bacteremia and sepsis. Treating these potentially dangerous infections have recently become more challenging due to the appearance of uropathogenic strains that are resistant to the many of the most commonly prescribed antibiotics. The majority of urinary tract infections (UTI) are caused by Escherichia coli, while another bacterium, Proteus mirabilis, is more likely to cause catheter-associated UTI. Here, we report that uropathogenic E. coli and P. mirabilis have divergent nutritional requirements despite growing in the same host environment. This result indicates that E. coli and P. mirabilis do not directly compete for nutrients during UTI. Indeed, we found that persistence of both pathogens is enhanced when they co-colonize the host. This work represents an important step toward understanding the basic nutritional requirements for two major pathogens that cause UTI and shows how mixed infections can change these requirements. Understanding how bacteria grow during infections is fundamental to ultimately uncover new ways to combat increasingly drug-resistant bacterial infections.
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Affiliation(s)
- Christopher J. Alteri
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Stephanie D. Himpsl
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Harry L. T. Mobley
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- * E-mail:
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12
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Pélissier MC, Sebban-Kreuzer C, Guerlesquin F, Brannigan JA, Bourne Y, Vincent F. Structural and functional characterization of the Clostridium perfringens N-acetylmannosamine-6-phosphate 2-epimerase essential for the sialic acid salvage pathway. J Biol Chem 2014; 289:35215-24. [PMID: 25320079 DOI: 10.1074/jbc.m114.604272] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pathogenic bacteria are endowed with an arsenal of specialized enzymes to convert nutrient compounds from their cell hosts. The essential N-acetylmannosamine-6-phosphate 2-epimerase (NanE) belongs to a convergent glycolytic pathway for utilization of the three amino sugars, GlcNAc, ManNAc, and sialic acid. The crystal structure of ligand-free NanE from Clostridium perfringens reveals a modified triose-phosphate isomerase (β/α)8 barrel in which a stable dimer is formed by exchanging the C-terminal helix. By retaining catalytic activity in the crystalline state, the structure of the enzyme bound to the GlcNAc-6P product identifies the topology of the active site pocket and points to invariant residues Lys(66) as a putative single catalyst, supported by the structure of the catalytically inactive K66A mutant in complex with substrate ManNAc-6P. (1)H NMR-based time course assays of native NanE and mutated variants demonstrate the essential role of Lys(66) for the epimerization reaction with participation of neighboring Arg(43), Asp(126), and Glu(180) residues. These findings unveil a one-base catalytic mechanism of C2 deprotonation/reprotonation via an enolate intermediate and provide the structural basis for the development of new antimicrobial agents against this family of bacterial 2-epimerases.
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Affiliation(s)
- Marie-Cécile Pélissier
- From the Aix-Marseille University, AFMB UMR7257, 163 avenue de Luminy 13288 Marseille, France, the CNRS, AFMB UMR7257, 163 avenue de Luminy, 13288 Marseille, France
| | - Corinne Sebban-Kreuzer
- the Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS UMR7255, Aix-Marseille Université, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France, and
| | - Françoise Guerlesquin
- the Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS UMR7255, Aix-Marseille Université, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France, and
| | - James A Brannigan
- the Department of Chemistry, Structural Biology Laboratory, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Yves Bourne
- From the Aix-Marseille University, AFMB UMR7257, 163 avenue de Luminy 13288 Marseille, France, the CNRS, AFMB UMR7257, 163 avenue de Luminy, 13288 Marseille, France
| | - Florence Vincent
- From the Aix-Marseille University, AFMB UMR7257, 163 avenue de Luminy 13288 Marseille, France, the CNRS, AFMB UMR7257, 163 avenue de Luminy, 13288 Marseille, France,
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13
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Coward C, Restif O, Dybowski R, Grant AJ, Maskell DJ, Mastroeni P. The effects of vaccination and immunity on bacterial infection dynamics in vivo. PLoS Pathog 2014; 10:e1004359. [PMID: 25233077 PMCID: PMC4169467 DOI: 10.1371/journal.ppat.1004359] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 07/25/2014] [Indexed: 01/31/2023] Open
Abstract
Salmonella enterica infections are a significant global health issue, and development of vaccines against these bacteria requires an improved understanding of how vaccination affects the growth and spread of the bacteria within the host. We have combined in vivo tracking of molecularly tagged bacterial subpopulations with mathematical modelling to gain a novel insight into how different classes of vaccines and branches of the immune response protect against secondary Salmonella enterica infections of the mouse. We have found that a live Salmonella vaccine significantly reduced bacteraemia during a secondary challenge and restrained inter-organ spread of the bacteria in the systemic organs. Further, fitting mechanistic models to the data indicated that live vaccine immunisation enhanced both the bacterial killing in the very early stages of the infection and bacteriostatic control over the first day post-challenge. T-cell immunity induced by this vaccine is not necessary for the enhanced bacteriostasis but is required for subsequent bactericidal clearance of Salmonella in the blood and tissues. Conversely, a non-living vaccine while able to enhance initial blood clearance and killing of virulent secondary challenge bacteria, was unable to alter the subsequent bacterial growth rate in the systemic organs, did not prevent the resurgence of extensive bacteraemia and failed to control the spread of the bacteria in the body. The bacterium Salmonella enterica causes gastroenteritis and the severe systemic diseases typhoid, paratyphoid fever and non-typhoidal septicaemia (NTS). Treatment of systemic disease with antibiotics is becoming increasingly difficult due to the acquisition of resistance. Licensed vaccines are available for the prevention of typhoid, but not paratyphoid fever or NTS. Vaccines can be either living (attenuated strains) or non-living (e.g. inactivated whole cells or surface polysaccharides) and these different classes potentially activate different components of the host immune system. Improvements in vaccine design require a better understanding of how different vaccine types differ in their ability to control a subsequent infection. We have improved a previously developed experimental system and mathematical model to investigate how these different vaccine types act. We show that the inactivated vaccine can only control bacterial numbers by a transient increase in bactericidal activity whereas the living vaccine is superior as it can induce an immune response that rapidly kills, then restrains the growth and spread of infecting bacteria.
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Affiliation(s)
- Chris Coward
- University of Cambridge, Department of Veterinary Medicine, Cambridge, United Kingdom
| | - Olivier Restif
- University of Cambridge, Department of Veterinary Medicine, Cambridge, United Kingdom
| | - Richard Dybowski
- University of Cambridge, Department of Veterinary Medicine, Cambridge, United Kingdom
| | - Andrew J Grant
- University of Cambridge, Department of Veterinary Medicine, Cambridge, United Kingdom
| | - Duncan J Maskell
- University of Cambridge, Department of Veterinary Medicine, Cambridge, United Kingdom
| | - Pietro Mastroeni
- University of Cambridge, Department of Veterinary Medicine, Cambridge, United Kingdom
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14
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Meadows JA, Wargo MJ. Catabolism of host-derived compounds during extracellular bacterial infections. J Cell Biochem 2014; 115:217-23. [PMID: 24038340 DOI: 10.1002/jcb.24664] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 09/03/2013] [Indexed: 11/07/2022]
Abstract
Efficient catabolism of host-derived compounds is essential for bacterial survival and virulence. While these links in intracellular bacteria are well studied, such studies in extracellular bacteria lag behind, mostly for technical reasons. The field has identified important metabolic pathways, but the mechanisms by which they impact infection and in particular, establishing the importance of a compound's catabolism versus alternate metabolic roles has been difficult. In this review we will examine evidence for catabolism during extracellular bacterial infections in animals and known or potential roles in virulence. In the process, we point out key gaps in the field that will require new or newly adapted techniques.
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Affiliation(s)
- Jamie A Meadows
- Department of Microbiology and Molecular Genetics, University of Vermont College of Medicine, Burlington, Vermont, 05405
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15
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Alternative strategies for proof-of-principle studies of antibacterial agents. Antimicrob Agents Chemother 2014; 58:4257-63. [PMID: 24867989 DOI: 10.1128/aac.02473-14] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The proof that a new antibacterial agent is not only active in vitro but also effective in vivo under clinically relevant conditions is currently provided (i) by using appropriate nonclinical models of infection and pharmacokinetic-pharmacodynamic (PK-PD) analysis providing evidence of the likelihood of clinical efficacy and (ii) by examining the study drug in exploratory clinical trials, as well as dose and schedule finding during phase II of clinical development. This approach is both time-consuming and costly. Furthermore, PK-PD targets for any novel antibacterial agent cannot be derived from studies with experimental animals. Therefore, alternative strategies have to be identified to prove the principle that a novel antibacterial agent is active under clinically relevant conditions. This review summarizes evidence that the quantitative analysis of shifts in the viable counts of pathogens in infected patients or the evaluation of the PD effect of an investigational agent on indicator organisms of the human resident microflora or colonizers of healthy volunteers, if paralleled with PK monitoring of serum and the target site, provides an alternative to a classical proof-of-principle study in the course of a phase II study program.
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16
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Rashid MU, Dalhoff A, Bäckström T, Björkhem-Bergman L, Panagiotidis G, Weintraub A, Nord CE. Ecological impact of MCB3837 on the normal human microbiota. Int J Antimicrob Agents 2014; 44:125-30. [PMID: 24931053 DOI: 10.1016/j.ijantimicag.2014.03.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 03/26/2014] [Accepted: 03/30/2014] [Indexed: 11/30/2022]
Abstract
MCB3837 is a novel, water-soluble, injectable prodrug that is rapidly converted to the active substance MCB3681 in vivo following intravenous (i.v.) administration. Both MCB3837 and MCB3681 are oxazolidinone-quinolone hybrid molecules. The purpose of the present study was to investigate the effect of MCB3681 on the human skin, nose, oropharyngeal and intestinal microbiota following administration of MCB3837. Twelve healthy male subjects received i.v. MCB3837 (6 mg/kg body weight) once daily for 5 days. Skin, nose, saliva and faecal samples were collected on Day -1 (pre dose), during administration on Days 2 and 5, and post dose on Days 8, 12 and 19. Micro-organisms were identified to genus level. No measurable concentrations of MCB3681 were found in any saliva samples or in the faecal samples on Day -1. On Day 2, 10 volunteers had faecal MCB3681 concentrations between 16.5 mg/kg faeces and 275.1mg/kg faeces; no MCB3681 in faeces could be detected in two of the volunteers. On Day 5, all volunteers had faecal concentrations of MCB3681 ranging from 98.9 to 226.3 mg/kg. MCB3681 caused no ecological changes in the skin, nasal and oropharyngeal microbiota. The numbers of enterococci, bifidobacteria, lactobacilli and clostridia decreased in the intestinal microbiota during administration of the drug. Numbers of Escherichia coli, other enterobacteria and Candida were not affected during the study. There was no impact on the number of Bacteroides. The faecal microbiota was normalised on Day 19. No new colonising aerobic or anaerobic Gram-positive bacteria with MCB3681 minimum inhibitory concentrations of ≥4 mg/L were found.
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Affiliation(s)
- Mamun-Ur Rashid
- Department of Laboratory Medicine, Karolinska University Hospital, Karolinska Institutet, SE-141 86 Stockholm, Sweden
| | - Axel Dalhoff
- University Medical Center Schleswig-Holstein, Institute for Infection Medicine, Brunswiker Str. 4, D-24105 Kiel, Germany
| | - Tobias Bäckström
- Department of Laboratory Medicine, Karolinska University Hospital, Karolinska Institutet, SE-141 86 Stockholm, Sweden
| | - Linda Björkhem-Bergman
- Department of Laboratory Medicine, Karolinska University Hospital, Karolinska Institutet, SE-141 86 Stockholm, Sweden
| | - Georgios Panagiotidis
- Department of Laboratory Medicine, Karolinska University Hospital, Karolinska Institutet, SE-141 86 Stockholm, Sweden
| | - Andrej Weintraub
- Department of Laboratory Medicine, Karolinska University Hospital, Karolinska Institutet, SE-141 86 Stockholm, Sweden
| | - Carl Erik Nord
- Department of Laboratory Medicine, Karolinska University Hospital, Karolinska Institutet, SE-141 86 Stockholm, Sweden.
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17
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Defoirdt T, Sorgeloos P. Monitoring of Vibrio harveyi quorum sensing activity in real time during infection of brine shrimp larvae. ISME JOURNAL 2012; 6:2314-9. [PMID: 22673627 DOI: 10.1038/ismej.2012.58] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Quorum sensing, bacterial cell-to-cell communication, has been linked to the virulence of pathogenic bacteria. Indeed, in vitro experiments have shown that many bacterial pathogens regulate the expression of virulence genes by this cell-to-cell communication process. Moreover, signal molecules have been detected in samples retrieved from infected hosts and quorum sensing disruption has been reported to result in reduced virulence in different host-pathogen systems. However, data on in vivo quorum sensing activity of pathogens during infection of a host are currently lacking. We previously reported that quorum sensing regulates the virulence of Vibrio harveyi in a standardised model system with gnotobiotic brine shrimp (Artemia franciscana) larvae. Here, we monitored quorum sensing activity in Vibrio harveyi during infection of the shrimp, using bioluminescence as a read-out. We found that wild-type Vibrio harveyi shows a strong increase in quorum sensing activity early during infection. In this respect, the bacteria behave remarkably similar in different larvae, despite the fact that only half of them survive the infection. Interestingly, when expressed per bacterial cell, Vibrio harveyi showed around 200-fold higher maximal quorum sensing-regulated bioluminescence when associated with larvae than in the culture water. Finally, the in vivo quorum sensing activity of mutants defective in the production of one of the three signal molecules is consistent with their virulence, with no detectable in vivo quorum sensing activity in AI-2- and CAI-1-deficient mutants. These results indicate that AI-2 and CAI-1 are the dominant signals during infection of brine shrimp.
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Affiliation(s)
- Tom Defoirdt
- Laboratory of Aquaculture & Artemia Reference Center, Ghent University, 9000 Gent, Belgium.
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18
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Macpherson HL, Bergh Ø, Birkbeck TH. An aerolysin-like enterotoxin from Vibrio splendidus may be involved in intestinal tract damage and mortalities in turbot, Scophthalmus maximus (L.), and cod, Gadus morhua L., larvae. JOURNAL OF FISH DISEASES 2012; 35:153-167. [PMID: 22233514 DOI: 10.1111/j.1365-2761.2011.01331.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Vibrio splendidus is a pathogen that can cause major losses during the early stages of larval turbot rearing when live feed (rotifers or Artemia) is used. As haemolytic bacteria have often been associated with larval rearing losses, we studied the role of the V. splendidus haemolysin in infection of larvae. From a bank of over 10,000 transposon mutants of V. splendidus, two different types of haemolysin-negative mutants were obtained. Both had lost virulence for larval fish, and immunohistochemistry showed that the transposon mutant studied colonized the turbot larval intestinal tract at a similar level to the wild-type organism but did not cause damage or signs of enteritis found with the wild-type organism. One transposon insertion site was located within a gene with high homology to aerolysin, the cytolytic toxin produced by several Aeromonas spp. The haemolysin, which we have termed vibrioaerolysin, had properties similar to aerolysin and osmotic protection studies showed that it formed pores in the membranes of erythrocytes of similar diameter to those of aerolysin. The Tn10 insertion site of the second transposon mutant was in an adjacent ToxR-like gene, suggesting that this might control expression of the vibrioaerolysin. The gastroenteritis caused by Aeromonas spp. in humans is considered to be due to production of aerolysin causing cyclic AMP-dependent chloride secretion in cells of the gastrointestinal tract. Damage to the intestinal tract of marine fish larvae could occur in a similar way, and it is possible that several Vibrio spp. found in the developing bacterial flora of the larval fish gut can secrete aerolysin-like toxins leading to death of larvae in the early rearing stages. Routine bacteriological screening on blood agar plates of live feed is recommended with measures to reduce the concentrations of haemolytic bacteria in rearing systems.
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Affiliation(s)
- H L Macpherson
- Division of Infection and Immunity, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, UK
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19
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Frizzo L, Soto L, Bertozzi E, Zbrun M, Signorini M, Sequeira G, Rodríguez Armesto R, Rosmini M. Intestinal populations of Lactobacilli and coliforms after in vivo Salmonella dublin challenge and their relationship with microbial translocation in calves supplemented with lactic acid bacteria and lactose. Anim Feed Sci Technol 2011. [DOI: 10.1016/j.anifeedsci.2011.07.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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20
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Venugopal A, Bryk R, Shi S, Rhee K, Rath P, Schnappinger D, Ehrt S, Nathan C. Virulence of Mycobacterium tuberculosis depends on lipoamide dehydrogenase, a member of three multienzyme complexes. Cell Host Microbe 2011; 9:21-31. [PMID: 21238944 DOI: 10.1016/j.chom.2010.12.004] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 10/18/2010] [Accepted: 12/01/2010] [Indexed: 01/24/2023]
Abstract
Mycobacterium tuberculosis (Mtb) adapts to persist in a nutritionally limited macrophage compartment. Lipoamide dehydrogenase (Lpd), the third enzyme (E3) in Mtb's pyruvate dehydrogenase complex (PDH), also serves as E1 of peroxynitrite reductase/peroxidase (PNR/P), which helps Mtb resist host-reactive nitrogen intermediates. In contrast to Mtb lacking dihydrolipoamide acyltransferase (DlaT), the E2 of PDH and PNR/P, Lpd-deficient Mtb is severely attenuated in wild-type and immunodeficient mice. This suggests that Lpd has a function that DlaT does not share. When DlaT is absent, Mtb upregulates an Lpd-dependent branched-chain keto acid dehydrogenase (BCKADH) encoded by pdhA, pdhB, pdhC, and lpdC. Without Lpd, Mtb cannot metabolize branched-chain amino acids and potentially toxic branched-chain intermediates accumulate. Mtb deficient in both DlaT and PdhC phenocopies Lpd-deficient Mtb. Thus, Mtb critically requires BCKADH along with PDH and PNR/P for pathogenesis. These findings position Lpd as a potential target for anti-infectives against Mtb.
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Affiliation(s)
- Aditya Venugopal
- Department of Microbiology and Immunology, Weill Cornell Medical College, 1300 York Avenue, New York, NY 10065, USA
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21
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Fang X, Wallqvist A, Reifman J. Development and analysis of an in vivo-compatible metabolic network of Mycobacterium tuberculosis. BMC SYSTEMS BIOLOGY 2010; 4:160. [PMID: 21092312 PMCID: PMC3225870 DOI: 10.1186/1752-0509-4-160] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 11/23/2010] [Indexed: 11/16/2022]
Abstract
Background During infection, Mycobacterium tuberculosis confronts a generally hostile and nutrient-poor in vivo host environment. Existing models and analyses of M. tuberculosis metabolic networks are able to reproduce experimentally measured cellular growth rates and identify genes required for growth in a range of different in vitro media. However, these models, under in vitro conditions, do not provide an adequate description of the metabolic processes required by the pathogen to infect and persist in a host. Results To better account for the metabolic activity of M. tuberculosis in the host environment, we developed a set of procedures to systematically modify an existing in vitro metabolic network by enhancing the agreement between calculated and in vivo-measured gene essentiality data. After our modifications, the new in vivo network contained 663 genes, 838 metabolites, and 1,049 reactions and had a significantly increased sensitivity (0.81) in predicted gene essentiality than the in vitro network (0.31). We verified the modifications generated from the purely computational analysis through a review of the literature and found, for example, that, as the analysis suggested, lipids are used as the main source for carbon metabolism and oxygen must be available for the pathogen under in vivo conditions. Moreover, we used the developed in vivo network to predict the effects of double-gene deletions on M. tuberculosis growth in the host environment, explore metabolic adaptations to life in an acidic environment, highlight the importance of different enzymes in the tricarboxylic acid-cycle under different limiting nutrient conditions, investigate the effects of inhibiting multiple reactions, and look at the importance of both aerobic and anaerobic cellular respiration during infection. Conclusions The network modifications we implemented suggest a distinctive set of metabolic conditions and requirements faced by M. tuberculosis during host infection compared with in vitro growth. Likewise, the double-gene deletion calculations highlight the importance of specific metabolic pathways used by the pathogen in the host environment. The newly constructed network provides a quantitative model to study the metabolism and associated drug targets of M. tuberculosis under in vivo conditions.
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Affiliation(s)
- Xin Fang
- Biotechnology HPC Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Materiel Command, Ft, Detrick, MD 21702, USA
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22
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Eisenreich W, Dandekar T, Heesemann J, Goebel W. Carbon metabolism of intracellular bacterial pathogens and possible links to virulence. Nat Rev Microbiol 2010; 8:401-12. [PMID: 20453875 DOI: 10.1038/nrmicro2351] [Citation(s) in RCA: 272] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
New technologies such as high-throughput methods and 13C-isotopologue-profiling analysis are beginning to provide us with insight into the in vivo metabolism of microorganisms, especially in the host cell compartments that are colonized by intracellular bacterial pathogens. In this Review, we discuss the recent progress made in determining the major carbon sources and metabolic pathways used by model intracellular bacterial pathogens that replicate either in the cytosol or in vacuoles of infected host cells. Furthermore, we highlight the possible links between intracellular carbon metabolism and the expression of virulence genes.
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Affiliation(s)
- Wolfgang Eisenreich
- Lehrstuhl für Biochemie, Technische Universität München, D-85747 Garching, Germany
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23
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In Vitro Synergy of Levofloxacin Plus Piperacillin/Tazobactam against Pseudomonas aeruginosa. Interdiscip Perspect Infect Dis 2009; 2009:984934. [PMID: 19911066 PMCID: PMC2774528 DOI: 10.1155/2009/984934] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 08/30/2009] [Accepted: 09/09/2009] [Indexed: 11/17/2022] Open
Abstract
In vitro synergy testing using levofloxacin (LVX) plus piperacillin/tazobactam (TZP) was performed by Etest and time-kill assay (TKA) for 31 unique fluoroquinolone-resistant Pseudomonas aeruginosa isolates. The Etest method showed synergy for 9/31 (29%) of isolates, while TKA showed synergy with 14/31 (45%) of isolates. When comparing the Etest method and TKA, concordant results for synergy, antagonism, and indifference were obtained for 24/31 (77%) of the isolates tested.
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Paterson GK, Cone DB, Northen H, Peters SE, Maskell DJ. Deletion of the gene encoding the glycolytic enzyme triosephosphate isomerase (tpi) alters morphology of Salmonella enterica serovar Typhimurium and decreases fitness in mice. FEMS Microbiol Lett 2009; 294:45-51. [PMID: 19493007 DOI: 10.1111/j.1574-6968.2009.01553.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The glycolytic enzyme triosephosphate isomerase (tpi) (EC 5.3.1.1) plays a key role in central carbon metabolism yet few studies have characterized isogenic bacterial mutants lacking this enzyme and none have examined its role in the in vivo fitness of a bacterial pathogen. Here we have deleted tpiA in Salmonella enterica serovar Typhimurium and found that the mutant had an altered morphology, displaying an elongated shape compared with the wild type. In a mouse model of typhoid fever the tpiA mutant was attenuated for growth as assessed by bacterial counts in the livers and spleens of infected mice. However, this attenuation was not deemed sufficient for consideration of a tpiA mutant as a live attenuated vaccine strain. These phenotypes were complemented by provision of tpiA on pBR322. We therefore provide the first demonstration that tpiA is required for full in vivo fitness of a bacterial pathogen, and that it has a discernable impact on cell morphology.
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Affiliation(s)
- Gavin K Paterson
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.
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25
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Paterson GK, Cone DB, Peters SE, Maskell DJ. Redundancy in the requirement for the glycolytic enzymes phosphofructokinase (Pfk) 1 and 2 in the in vivo fitness of Salmonella enterica serovar Typhimurium. Microb Pathog 2009; 46:261-5. [PMID: 19486643 DOI: 10.1016/j.micpath.2009.01.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Revised: 01/22/2009] [Accepted: 01/29/2009] [Indexed: 10/21/2022]
Abstract
To assess the role of the glycolytic enzyme phosphofructokinase (Pfk) in the in vivo fitness of the pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) we have generated single and double gene deletion mutants of the two known isoforms of this enzyme, pfkA and pfkB. In a mouse model of typhoid fever, bacterial counts in the spleen and liver were similar between wild type and single pfkA and pfkB mutant-infected mice. However, a double pfkAB mutant was significantly attenuated for growth in vivo. This defect was complemented by provision of either pfkA or pfkB on pBR322. Together these data show that Pfk activity is required for the full in vivo fitness of S. Typhimurium with functional redundancy between pfkA and pfkB. The level of attenuation of the pfkAB double mutant was not sufficient for its consideration as a live attenuated vaccine strain.
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Affiliation(s)
- G K Paterson
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK.
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Modelling within-host spatiotemporal dynamics of invasive bacterial disease. PLoS Biol 2008; 6:e74. [PMID: 18399718 PMCID: PMC2288627 DOI: 10.1371/journal.pbio.0060074] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Accepted: 02/13/2008] [Indexed: 12/16/2022] Open
Abstract
Mechanistic determinants of bacterial growth, death, and spread within mammalian hosts cannot be fully resolved studying a single bacterial population. They are also currently poorly understood. Here, we report on the application of sophisticated experimental approaches to map spatiotemporal population dynamics of bacteria during an infection. We analyzed heterogeneous traits of simultaneous infections with tagged Salmonella enterica populations (wild-type isogenic tagged strains [WITS]) in wild-type and gene-targeted mice. WITS are phenotypically identical but can be distinguished and enumerated by quantitative PCR, making it possible, using probabilistic models, to estimate bacterial death rate based on the disappearance of strains through time. This multidisciplinary approach allowed us to establish the timing, relative occurrence, and immune control of key infection parameters in a true host–pathogen combination. Our analyses support a model in which shortly after infection, concomitant death and rapid bacterial replication lead to the establishment of independent bacterial subpopulations in different organs, a process controlled by host antimicrobial mechanisms. Later, decreased microbial mortality leads to an exponential increase in the number of bacteria that spread locally, with subsequent mixing of bacteria between organs via bacteraemia and further stochastic selection. This approach provides us with an unprecedented outlook on the pathogenesis of S. enterica infections, illustrating the complex spatial and stochastic effects that drive an infectious disease. The application of the novel method that we present in appropriate and diverse host–pathogen combinations, together with modelling of the data that result, will facilitate a comprehensive view of the spatial and stochastic nature of within-host dynamics. Global patterns and mechanistic determinants of bacterial spread in mammalian organisms are difficult to obtain through numerical and topographical mapping of a single bacterial population. Appreciation of the true pathogenetic events during infections needs to be based on the understanding of the fine interactions that control the infection dynamics of individual subpopulations in the same host. We have used molecular techniques to tag individually otherwise identical subpopulations of bacteria. We have used these bacteria, called wild-type isogenic tagged strains (WITS), in simultaneous infections in the same animal to gather insights into the patterns of spread of individual subpopulations of bacteria in the tissues and interactions between bacteria and phagocytes. Combining numerical fluctuation in the WITS populations with mathematical modelling and statistical analysis, we have gathered data on the relative occurrence of bacterial growth and death in different phases of the disease process. Our analyses support a model in which shortly after infection, concomitant death and rapid bacterial replication lead to the establishment of independent bacterial subpopulations in different organs. Later, decreased microbial mortality leads to an exponential increase in the number of bacteria that spread locally, with subsequent mixing of bacteria between organs. The work illustrates the importance of unravelling heterogeneous traits of infections to reconstruct and understand the true nature of the global disease process. Genetically identical bacterial strains reveal the population dynamics and interactions of subpopulations of bacteria with the host's immune system in vivo during infection.
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Abstract
We characterized two sucrose-metabolizing systems -sus and scr- and describe their roles in the physiology and virulence of Streptococcus pneumoniae in murine models of carriage and pneumonia. The sus and scr systems are regulated by LacI family repressors SusR and ScrR respectively. SusR regulates an adjacent ABC transporter (susT1/susT2/susX) and sucrose-6-phosphate (S-6-P) hydrolase (susH). ScrR controls an adjacent PTS transporter (scrT), fructokinase (scrK) and second S-6-P hydrolase (scrH). sus and scr play niche-specific roles in virulence. The susH and sus locus mutants are attenuated in the lung, but dispensable in nasopharyngeal carriage. Conversely, the scrH and scr locus mutants, while dispensable in the lung, are attenuated for nasopharyngeal colonization. The scrH/susH double mutant is more attenuated than scrH in the nasopharynx, indicating SusH can substitute in this niche. Both systems are sucrose-inducible, with ScrH being the major in vitro hydrolase. The scrH/susH mutant does not grow on sucrose indicating that sus and scr are the only sucrose-metabolizing systems in S. pneumoniae. We propose a model describing hierarchical regulation of the scr and sus systems by the putative inducer, S-6-P. The transport and metabolism of sucrose or a related disaccharide thus contributes to S. pneumoniae colonization and disease.
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Affiliation(s)
- Ramkumar Iyer
- Howard Hughes Medical Institute, 136 Harrison Avenue, Tufts University, Boston, MA 02110, USA
| | - Andrew Camilli
- Department of Molecular Biology and Microbiology, 136 Harrison Avenue, Tufts University, Boston, MA 02110, USA
- For correspondence. ; Tel. (+1) 617 636 6933; Fax (+1) 617 636 2175
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Smith H, Tang CM, Exley RM. Effect of host lactate on gonococci and meningococci: new concepts on the role of metabolites in pathogenicity. Infect Immun 2007; 75:4190-8. [PMID: 17562766 PMCID: PMC1951187 DOI: 10.1128/iai.00117-07] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Affiliation(s)
- Harry Smith
- The Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
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Hodgson JC. Endotoxin and Mammalian Host Responses During Experimental Disease. J Comp Pathol 2006; 135:157-75. [PMID: 17101336 DOI: 10.1016/j.jcpa.2006.09.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2006] [Accepted: 09/04/2006] [Indexed: 10/23/2022]
Abstract
Endotoxin is an integral component of the outer membrane of Gram-negative bacteria and a prime example of unique and highly conserved bacterial surface molecules that engage with the innate immune system of the mammalian host via pattern recognition receptors on a range of host cells. The results of this interaction, which may be beneficial or detrimental to the development and welfare of the host, are reviewed, focusing on the different sensitivities and consequences in a range of hosts of experimental exposure to endotoxin, the disease outcomes and recent developments in our understanding of the mechanisms involved.
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Affiliation(s)
- J C Hodgson
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian EH26 0PZ, UK.
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Muñoz-Elías EJ, Upton AM, Cherian J, McKinney JD. Role of the methylcitrate cycle in Mycobacterium tuberculosis metabolism, intracellular growth, and virulence. Mol Microbiol 2006; 60:1109-22. [PMID: 16689789 DOI: 10.1111/j.1365-2958.2006.05155.x] [Citation(s) in RCA: 251] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Growth of bacteria and fungi on fatty acid substrates requires the catabolic beta-oxidation cycle and the anaplerotic glyoxylate cycle. Propionyl-CoA generated by beta-oxidation of odd-chain fatty acids is metabolized via the methylcitrate cycle. Mycobacterium tuberculosis possesses homologues of methylcitrate synthase (MCS) and methylcitrate dehydratase (MCD) but not 2-methylisocitrate lyase (MCL). Although MCLs share limited homology with isocitrate lyases (ICLs) of the glyoxylate cycle, these enzymes are thought to be functionally non-overlapping. Previously we reported that the M. tuberculosis ICL isoforms 1 and 2 are jointly required for growth on fatty acids, in macrophages, and in mice. ICL-deficient bacteria could not grow on propionate, suggesting that in M. tuberculosis ICL1 and ICL2 might function as ICLs in the glyoxylate cycle and as MCLs in the methylcitrate cycle. Here we provide biochemical and genetic evidence supporting this interpretation. The role of the methylcitrate cycle in M. tuberculosis metabolism was further evaluated by constructing a mutant strain in which prpC (encoding MCS) and prpD (encoding MCD) were deleted. The DeltaprpDC strain could not grow on propionate media in vitro or in murine bone marrow-derived macrophages infected ex vivo; growth under these conditions was restored by complementation with a plasmid containing prpDC. Paradoxically, bacterial growth and persistence, and tissue pathology, were indistinguishable in mice infected with wild-type or DeltaprpDC bacteria.
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Affiliation(s)
- Ernesto J Muñoz-Elías
- Laboratory of Infection Biology, The Rockefeller University, New York, NY 10021, USA
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Abstract
Bacterial metabolism has been studied intensively since the first observations of these 'animalcules' by Leeuwenhoek and their isolation in pure cultures by Pasteur. Metabolic studies have traditionally focused on a small number of model organisms, primarily the Gram negative bacillus Escherichia coli, adapted to artificial culture conditions in the laboratory. Comparatively little is known about the physiology and metabolism of wild microorganisms living in their natural habitats. For approximately 500-1000 species of commensals and symbionts, and a smaller number of pathogenic bacteria, that habitat is the human body. Emerging evidence suggests that the metabolism of bacteria grown in vivo differs profoundly from their metabolism in axenic cultures.
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Affiliation(s)
- Ernesto J Muñoz-Elías
- Laboratory of Infection Biology, The Rockefeller University, New York, NY 10021, USA
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Salim KY, Cvitkovitch DG, Chang P, Bast DJ, Handfield M, Hillman JD, de Azavedo JCS. Identification of group A Streptococcus antigenic determinants upregulated in vivo. Infect Immun 2005; 73:6026-38. [PMID: 16113323 PMCID: PMC1231132 DOI: 10.1128/iai.73.9.6026-6038.2005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Group A Streptococcus (GAS) causes a range of diseases in humans, from mild noninvasive infections to severe invasive infections. The molecular basis for the varying severity of disease remains unclear. We identified genes expressed during invasive disease using in vivo-induced antigen technology (IVIAT), applied for the first time in a gram-positive organism. Convalescent-phase sera from patients with invasive disease were pooled, adsorbed against antigens derived from in vitro-grown GAS, and used to screen a GAS genomic expression library. A murine model of invasive GAS disease was included as an additional source of sera for screening. Sequencing DNA inserts from clones reactive with both human and mouse sera indicated 16 open reading frames with homology to genes involved in metabolic activity to genes of unknown function. Of these, seven genes were assessed for their differential expression by quantitative real-time PCR both in vivo, utilizing a murine model of invasive GAS disease, and in vitro at different time points of growth. Three gene products-a putative penicillin-binding protein 1A, a putative lipoprotein, and a conserved hypothetical protein homologous to a putative translation initiation inhibitor in Vibrio vulnificus-were upregulated in vivo, suggesting that these genes play a role during invasive disease.
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Affiliation(s)
- Kowthar Y Salim
- Department of Microbiology, University of Toronto, Toronto, Ontario, Canada
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Pankey GA, Ashcraft DS. In vitro synergy of ciprofloxacin and gatifloxacin against ciprofloxacin-resistant Pseudomonas aeruginosa. Antimicrob Agents Chemother 2005; 49:2959-64. [PMID: 15980375 PMCID: PMC1168659 DOI: 10.1128/aac.49.7.2959-2964.2005] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Multidrug-resistant Pseudomonas aeruginosa with combined decreased susceptibility to ceftazidime, ciprofloxacin, imipenem, and piperacillin is increasingly being found as a cause of nosocomial infections. It is important to look for combinations of drugs that might be synergistic. Ciprofloxacin resistance by P. aeruginosa is mediated in part by an efflux pump mechanism. Gatifloxacin, an 8-methoxyfluoroquinolone, inhibits a staphylococcal efflux pump. An earlier in vitro study using an Etest synergy method and time-kill assay suggested synergy of ciprofloxacin and gatifloxacin against P. aeruginosa. Synergy testing was performed by Etest and time-kill assay for 31 clinically unique, plasmid DNA distinct, U.S. P. aeruginosa isolates. Etest MICs for ciprofloxacin were 4 to >32 microg/ml, and for gatifloxacin they were >32 microg/ml. Ciprofloxacin plus gatifloxacin showed synergy by the Etest method for 6 (19%) of the 31 P. aeruginosa isolates using a summation fractional inhibitory concentration of < or = 0.5 for synergy. Synergy was demonstrated for 13/31 (42%) of isolates by time-kill assay. No antagonism was detected. The remaining isolates were indifferent to the combination. The Etest method and time-kill assay were 65% (20/31) concordant. The mechanism of the in vitro synergy may include P. aeruginosa ciprofloxacin efflux pump inhibition by gatifloxacin.
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Affiliation(s)
- George A Pankey
- Infectious Diseases Research, Ochsner Clinic Foundation, 1514 Jefferson Highway, New Orleans, Louisiana 70121, USA.
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Muñoz-Elías EJ, McKinney JD. Mycobacterium tuberculosis isocitrate lyases 1 and 2 are jointly required for in vivo growth and virulence. Nat Med 2005; 11:638-44. [PMID: 15895072 PMCID: PMC1464426 DOI: 10.1038/nm1252] [Citation(s) in RCA: 557] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2004] [Accepted: 04/29/2005] [Indexed: 01/01/2023]
Abstract
Genes involved in fatty acid catabolism have undergone extensive duplication in the genus Mycobacterium, which includes the etiologic agents of leprosy and tuberculosis. Here, we show that prokaryotic- and eukaryotic-like isoforms of the glyoxylate cycle enzyme isocitrate lyase (ICL) are jointly required for fatty acid catabolism and virulence in Mycobacterium tuberculosis. Although deletion of icl1 or icl2, the genes that encode ICL1 and ICL2, respectively, had little effect on bacterial growth in macrophages and mice, deletion of both genes resulted in complete impairment of intracellular replication and rapid elimination from the lungs. The feasibility of targeting ICL1 and ICL2 for chemical inhibition was shown using a dual-specific ICL inhibitor, which blocked growth of M. tuberculosis on fatty acids and in macrophages. The absence of ICL orthologs in mammals should facilitate the development of glyoxylate cycle inhibitors as new drugs for the treatment of tuberculosis.
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Affiliation(s)
| | - John D. McKinney
- Laboratory of Infection Biology, The Rockefeller University, New York, NY 10021 USA
- *Corresponding author: John D. McKinney, Ph.D. Laboratory of Infection Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10021 USA. Tel: (+1) 212-327-7081. Fax: (+1) 212-327-7083. E-mail:
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Mahan MJ, Heithoff DM, Sinsheimer RL, Low DA. Assessment of bacterial pathogenesis by analysis of gene expression in the host. Annu Rev Genet 2001; 34:139-164. [PMID: 11092824 DOI: 10.1146/annurev.genet.34.1.139] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A number of techniques have been developed to assess the expression of microbial virulence genes within the host (in vivo). These studies have shown that bacteria employ a wide variety of mechanisms to coordinately regulate the expression of these genes during infection. Two tenets have emerged from these studies: bacterial adaptation responses are critical to growth within the host, and interactions between microorganisms and the microenvironments of their hosts cannot be revealed from in vitro studies alone. Results that support these tenets include (i) the prevalent class of in vivo expressed genes are involved in adaptation to environmental stresses, (ii) pathogens recovered from host tissues (versus laboratory growth) are often more resistant to host killing mechanisms, and (iii) virulence gene expression can differ in the animal compared to laboratory media. Thus, pathogenicity comprises the unique ability to adapt to the varied host milieus encountered as the infection proceeds.
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Affiliation(s)
- M J Mahan
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA.
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Abstract
Slalic acids are one of the most important molecules of life, since they occupy the terminal position on macromolecules and cell membranes and are involved in many biological and pathological phenomena. The structures of sialic acids, comprising a family of over 40 neuraminic acid derivatives, have been elucidated. However, many aspects of the regulation of their metabolism at the enzyme and gene levels, as well as of their functions remain mysterious. Sialic acids play a dual role, not only are they indispensable for the protection to and adaptation of life, but are also utilised by life-threatening infectious microorganisms. In this article the present state of knowledge in sialobiology, with an emphasis on my personal experience in this research area, is outlined including a discussion of necessary future work in this fascinating field of cell biology.
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Affiliation(s)
- R Schauer
- Biochemisches Institut, Christian-Albrechts-Universität, Kiel, Germany.
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