301
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Li W, He ZG. LtmA, a novel cyclic di-GMP-responsive activator, broadly regulates the expression of lipid transport and metabolism genes in Mycobacterium smegmatis. Nucleic Acids Res 2012; 40:11292-307. [PMID: 23047950 PMCID: PMC3526308 DOI: 10.1093/nar/gks923] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
In a bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP)/transcription factor binding screen, we identified Mycobacterium smegmatis Ms6479 as the first c-di-GMP-responsive transcriptional factor in mycobacteria. Ms6479 could specifically bind with c-di-GMP and recognize the promoters of 37 lipid transport and metabolism genes. c-di-GMP could enhance the ability of Ms6479 to bind to its target DNA. Furthermore, our results establish Ms6479 as a global activator that positively regulates the expression of diverse target genes. Overexpression of Ms6479 in M. smegmatis significantly reduced the permeability of the cell wall to crystal violet and increased mycobacterial resistance to anti-tuberculosis antibiotics. Interestingly, Ms6479 lacks the previously reported c-di-GMP binding motifs. Our findings introduce Ms6479 (here designated LtmA for lipid transport and metabolism activator) as a new c-di-GMP-responsive regulator.
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Affiliation(s)
- Weihui Li
- National Key Laboratory of Agricultural Microbiology, Center for Proteomics Research, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
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302
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Robinson CM, Jung JY, Nau GJ. Interferon-γ, tumor necrosis factor, and interleukin-18 cooperate to control growth of Mycobacterium tuberculosis in human macrophages. Cytokine 2012; 60:233-41. [PMID: 22749533 PMCID: PMC3429699 DOI: 10.1016/j.cyto.2012.06.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Revised: 04/25/2012] [Accepted: 06/04/2012] [Indexed: 12/19/2022]
Abstract
Mycobacterium tuberculosis (MTB) remains a leading infectious threat to human health. Macrophages are the cells targeted for infection by the bacterium as well as key effector cells for clearance of the pathogen. Interleukin (IL)-27 opposes macrophage-mediated control of MTB because supplying IL-12 and blocking the activity of IL-27 limits bacterial growth in primary human macrophages. The purpose of this study was to determine the immunological regulators of this macrophage mechanism to restrict MTB growth. Interferon (IFN)-γ, TNF-α, and IL-18 were all demonstrated to be important to the environment that limits bacterial growth when IL-12 is supplied and IL-27 is neutralized. We find IL-18 works in conjunction with IL-12 to achieve optimal IFN-γ production in this system. We also demonstrate novel interactions between these cytokines to influence the expression or responsiveness to one another. Quantitative assays show that IFN-γ enhances expression of the IL-18 receptor signaling chain, as well as TNF expression and secretion. In turn, TNF-α augments expression of the receptor for IFN-γ, the amount at the cell surface, and the extent of IFN-γ -induced signaling. We further define how the cytokine environment supports an enhanced state of classical macrophage activation. Collectively, these results describe novel immunological mechanisms that provide additional insights into the effects of IL-12 and IL-27 on macrophage regulation during MTB infection.
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Affiliation(s)
- Cory M Robinson
- Department of Pathology, Microbiology, and Immunology, University of South Carolina School of Medicine, Columbia, SC 29209, USA.
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303
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Pan J, Bahar AA, Syed H, Ren D. Reverting antibiotic tolerance of Pseudomonas aeruginosa PAO1 persister cells by (Z)-4-bromo-5-(bromomethylene)-3-methylfuran-2(5H)-one. PLoS One 2012; 7:e45778. [PMID: 23029239 PMCID: PMC3447867 DOI: 10.1371/journal.pone.0045778] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 08/24/2012] [Indexed: 01/23/2023] Open
Abstract
Background Bacteria are well known to form dormant persister cells that are tolerant to most antibiotics. Such intrinsic tolerance also facilitates the development of multidrug resistance through acquired mechanisms. Thus persister cells are a promising target for developing more effective methods to control chronic infections and help prevent the development of multidrug-resistant bacteria. However, control of persister cells is still an unmet challenge. Methodology/Principal Findings We show in this report that (Z)-4-bromo-5-(bromomethylene)-3-methylfuran-2(5H)-one (BF8) can restore the antibiotic susceptibility of Pseudomonas aeruginosa PAO1 persister cells at growth non-inhibitory concentrations. Persister control by BF8 was found to be effective against both planktonic and biofilm cells of P. aeruginosa PAO1. Interestingly, although BF8 is an inhibitor of quorum sensing (QS) in Gram-negative bacteria, the data in this study suggest that the activities of BF8 to revert antibiotic tolerance of P. aeruginosa PAO1 persister cells is not through QS inhibition and may involve other targets. Conclusion BF8 can sensitize P. aeruginosa persister cells to antibiotics.
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Affiliation(s)
- Jiachuan Pan
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York, United States of America
- Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York, United States of America
| | - Ali Adem Bahar
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York, United States of America
- Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York, United States of America
| | - Haseeba Syed
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York, United States of America
- Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York, United States of America
| | - Dacheng Ren
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York, United States of America
- Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York, United States of America
- Department of Civil and Environmental Engineering, Syracuse University, Syracuse, New York, United States of America
- Department of Biology, Syracuse University, Syracuse, New York, United States of America
- * E-mail:
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304
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Franzblau SG, DeGroote MA, Cho SH, Andries K, Nuermberger E, Orme IM, Mdluli K, Angulo-Barturen I, Dick T, Dartois V, Lenaerts AJ. Comprehensive analysis of methods used for the evaluation of compounds against Mycobacterium tuberculosis. Tuberculosis (Edinb) 2012; 92:453-88. [PMID: 22940006 DOI: 10.1016/j.tube.2012.07.003] [Citation(s) in RCA: 159] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Revised: 07/02/2012] [Accepted: 07/09/2012] [Indexed: 02/01/2023]
Abstract
In drug development, there are typically a series of preclinical studies that must be completed with new compounds or regimens before use in humans. A sequence of in vitro assays followed by in vivo testing in validated animal models to assess the activity against Mycobacterium tuberculosis, pharmacology and toxicity is generally used for advancing compounds against tuberculosis in a preclinical stage. A plethora of different assay systems and conditions are used to study the effect of drug candidates on the growth of M. tuberculosis, making it difficult to compare data from one laboratory to another. The Bill and Melinda Gates Foundation recognized the scientific gap to delineate the spectrum of variables in experimental protocols, identify which of these are biologically significant, and converge towards a rationally derived standard set of optimized assays for evaluating compounds. The goals of this document are to recommend protocols and hence accelerate the process of TB drug discovery and testing. Data gathered from preclinical in vitro and in vivo assays during personal visits to laboratories and an electronic survey of methodologies sent to investigators is reported. Comments, opinions, experiences as well as final recommendations from those currently engaged in such preclinical studies for TB drug testing are being presented. Certain in vitro assays and mouse efficacy models were re-evaluated in the laboratory as head-to-head experiments and a summary is provided on the results obtained. It is our hope that this information will be a valuable resource for investigators in the field to move forward in an efficient way and that key variables of assays are included to ensure accuracy of results which can then be used for designing human clinical trials. This document then concludes with remaining questions and critical gaps that are in need of further validation and experimentation.
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Affiliation(s)
- Scott G Franzblau
- Institute for Tuberculosis Research, College of Pharmacy, University of Illinois at Chicago, 833 S Wood Street, Chicago, IL 60621-7231, USA
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305
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Marine-derived fungal sesterterpenes, ophiobolins, inhibit biofilm formation of Mycobacterium species. J Nat Med 2012; 67:271-5. [DOI: 10.1007/s11418-012-0676-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 05/17/2012] [Indexed: 11/27/2022]
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306
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Verschoor JA, Baird MS, Grooten J. Towards understanding the functional diversity of cell wall mycolic acids of Mycobacterium tuberculosis. Prog Lipid Res 2012; 51:325-39. [PMID: 22659327 DOI: 10.1016/j.plipres.2012.05.002] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Revised: 03/05/2012] [Accepted: 05/23/2012] [Indexed: 01/08/2023]
Abstract
Mycolic acids constitute the waxy layer of the outer cell wall of Mycobacterium spp. and a few other genera. They are diverse in structure, providing a unique chromatographic foot-print for almost each of the more than 70 Mycobacterium species. Although mainly esterified to cell wall arabinogalactan, trehalose or glucose, some free mycolic acid is secreted during in vitro growth of Mycobacterium tuberculosis. In M. tuberculosis, α-, keto- and methoxy-mycolic acids are the main classes, each differing in their ability to attract neutrophils, induce foamy macrophages or adopt an antigenic structure for antibody recognition. Of interest is their particular relationship to cholesterol, discovered by their ability to attract cholesterol, to bind Amphotericin B or to be recognised by monoclonal antibodies that cross-react with cholesterol. The structural elements that determine this diverse functionality include the carboxylic acid in the mycolic motif, as well as the nature and stereochemistry of the two functional groups in the merochain. The functional diversity of mycolic acid classes implies that much information may be contained in the selective expression and secretion of mycolic acids to establish tuberculosis after infection of the host. Their cholesteroid nature may relate to how they utilize host cholesterol for their persistent survival.
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Affiliation(s)
- Jan A Verschoor
- Department Biochemistry, University of Pretoria, Pretoria 0002, South Africa.
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307
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Brambilla C, Sánchez-Chardi A, Pérez-Trujillo M, Julián E, Luquin M. Cyclopropanation of α-mycolic acids is not required for cording in Mycobacterium brumae and Mycobacterium fallax. MICROBIOLOGY-SGM 2012; 158:1615-1621. [PMID: 22493302 DOI: 10.1099/mic.0.057919-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The capacity to form microscopic cords (cording) of Mycobacterium species has been related to their virulence. The compounds responsible for cording are unknown, but a recent study has shown that cording could be related to the fine structure of α-mycolic acids. This investigation attributes the need for a proximal cyclopropane in α-mycolic acids for cording in Mycobacterium tuberculosis and Mycobacterium bovis BCG and proposes cyclopropanases as good targets for new chemotherapeutic agents. As other Mycobacterium species in addition to M. tuberculosis and M. bovis form microscopic cords, it would be of major interest to know whether the relationship between proximal cyclopropanation of α-mycolic acids and cording could be extended to non-tuberculous mycobacteria. In this study, we have examined the correlation between the cording and cyclopropanation of α-mycolic acids in two species, Mycobacterium brumae and Mycobacterium fallax. Scanning electron microscopy images showed, for the first time to our knowledge, the fine structure of microscopic cords of M. brumae and M. fallax, confirming that these two species form true cords. Furthermore, NMR analysis performed on the same cording cultures corroborates the absence of cyclopropane rings in their α-mycolic acids. Therefore, we can conclude that the correlation between cording and cyclopropanation of α-mycolic acids cannot be extended to all mycobacteria. As M. brumae and M. fallax grow rapidly and have a simple pattern of mycolic acids (only α-unsaturated mycolic acids), we propose these two species as suitable models for the study of the role of mycolic acids in cording.
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Affiliation(s)
- Cecilia Brambilla
- Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Barcelona, Spain
| | | | - Míriam Pérez-Trujillo
- Servei de Ressonància Magnètica Nuclear, Universitat Autònoma de Barcelona, 08193 Barcelona, Spain
| | - Esther Julián
- Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Barcelona, Spain
| | - Marina Luquin
- Departament de Genètica i de Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Barcelona, Spain
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308
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Abstract
Mycobacterium tuberculosis, the etiologic agent of human tuberculosis, has an extraordinary ability to survive against environmental stresses including antibiotics. Although stress tolerance of M. tuberculosis is one of the likely contributors to the 6-month long chemotherapy of tuberculosis (1), the molecular mechanisms underlying this characteristic phenotype of the pathogen remain unclear. Many microbial species have evolved to survive in stressful environments by self-assembling in highly organized, surface attached, and matrix encapsulated structures called biofilms (2-4). Growth in communities appears to be a preferred survival strategy of microbes, and is achieved through genetic components that regulate surface attachment, intercellular communications, and synthesis of extracellular polymeric substances (EPS) (5,6). The tolerance to environmental stress is likely facilitated by EPS, and perhaps by the physiological adaptation of individual bacilli to heterogeneous microenvironments within the complex architecture of biofilms (7). In a series of recent papers we established that M. tuberculosis and Mycobacterium smegmatis have a strong propensity to grow in organized multicellular structures, called biofilms, which can tolerate more than 50 times the minimal inhibitory concentrations of the anti-tuberculosis drugs isoniazid and rifampicin (8-10). M. tuberculosis, however, intriguingly requires specific conditions to form mature biofilms, in particular 9:1 ratio of headspace: media as well as limited exchange of air with the atmosphere (9). Requirements of specialized environmental conditions could possibly be linked to the fact that M. tuberculosis is an obligate human pathogen and thus has adapted to tissue environments. In this publication we demonstrate methods for culturing M. tuberculosis biofilms in a bottle and a 12-well plate format, which is convenient for bacteriological as well as genetic studies. We have described the protocol for an attenuated strain of M. tuberculosis, mc(2)7000, with deletion in the two loci, panCD and RD1, that are critical for in vivo growth of the pathogen (9). This strain can be safely used in a BSL-2 containment for understanding the basic biology of the tuberculosis pathogen thus avoiding the requirement of an expensive BSL-3 facility. The method can be extended, with appropriate modification in media, to grow biofilm of other culturable mycobacterial species. Overall, a uniform protocol of culturing mycobacterial biofilms will help the investigators interested in studying the basic resilient characteristics of mycobacteria. In addition, a clear and concise method of growing mycobacterial biofilms will also help the clinical and pharmaceutical investigators to test the efficacy of a potential drug.
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Affiliation(s)
- Kathleen Kulka
- Department of Infectious Diseases and Microbiology, University of Pittsburgh, Pittsburgh, PA, USA
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309
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Vergidis P, Lesnick T, Kremers W, Razonable R. Prosthetic joint infection in solid organ transplant recipients: a retrospective case-control study. Transpl Infect Dis 2012; 14:380-6. [DOI: 10.1111/j.1399-3062.2011.00708.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 08/19/2011] [Accepted: 10/06/2011] [Indexed: 01/21/2023]
Affiliation(s)
| | - T.G. Lesnick
- Division of Biomedical Statistics and Informatics; College of Medicine; Mayo Clinic; Rochester; Minnesota; USA
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310
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Low dose aerosol fitness at the innate phase of murine infection better predicts virulence amongst clinical strains of Mycobacterium tuberculosis. PLoS One 2012; 7:e29010. [PMID: 22235258 PMCID: PMC3250398 DOI: 10.1371/journal.pone.0029010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Accepted: 11/18/2011] [Indexed: 01/06/2023] Open
Abstract
Background Evaluation of a quick and easy model to determine the intrinsic ability of clinical strains to generate active TB has been set by assuming that this is linked to the fitness of Mycobacterium tuberculosis strain at the innate phase of the infection. Thus, the higher the bacillary load, the greater the possibility of inducting liquefaction, and thus active TB, once the adaptive response is set. Methodology/Principal Findings The virulence of seven clinical Mycobacterium tuberculosis strains isolated in Spain was tested by determining the bacillary concentration in the spleen and lung of mice at weeks 0, 1 and 2 after intravenous (IV) inoculation of 104 CFU, and by determining the growth in vitro until the stationary phase had been reached. Cord distribution automated analysis showed two clear patterns related to the high and low fitness in the lung after IV infection. This pattern was not seen in the in vitro fitness tests, which clearly favored the reference strain (H37Rv). Subsequent determination using a more physiological low-dose aerosol (AER) inoculation with 102 CFU showed a third pattern in which the three best values coincided with the highest dissemination capacity according to epidemiological data. Conclusions/Significance The fitness obtained after low dose aerosol administration in the presence of the innate immune response is the most predictive factor for determining the virulence of clinical strains. This gives support to a mechanism of the induction of active TB derived from the dynamic hypothesis of latent tuberculosis infection.
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311
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Soluble Urokinase Plasminogen Activator Receptor Levels in Tuberculosis Patients at High Risk for Multidrug Resistance. Tuberc Res Treat 2012; 2012:240132. [PMID: 23304490 PMCID: PMC3532865 DOI: 10.1155/2012/240132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 11/19/2012] [Indexed: 11/17/2022] Open
Abstract
The soluble urokinase plasminogen activator receptor (suPAR) has been shown to be a strong prognostic biomarker for tuberculosis (TB). In the present study, the profiles of plasma suPAR levels in pulmonary TB patients at high risk for multidrug resistance were analyzed and compared with those in multidrug resistant (MDR)-TB patients. Forty patients were prospectively included, consisting of 10 MDR-TB patients and 30 TB patients at high risk for MDR, underwent clinical assesment. Plasma suPAR levels were measured using ELISA (SUPARnostic, Denmark) and bacterial cultures were performed in addition to drug susceptibility tests. All patients of suspected MDR-TB group demonstrated significantly higher suPAR levels compared with the healthy TB-negative group (1.79 ng/mL). Among the three groups at high risk for MDR-TB, only the relapse group (7.87 ng/mL) demonstrated suPAR levels comparable with those of MDR-TB patients (7.67 ng/mL). suPAR levels in the two-month negative acid-fast bacilli conversion group (9.29 ng/mL) were higher than positive control, whereas levels in the group consisting of therapy failure patients (5.32 ng/mL) were lower. Our results strongly suggest that suPAR levels enable rapid screening of suspected MDR-TB patients, but cannot differentiate between groups.
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312
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Uptake of sulfate but not phosphate by Mycobacterium tuberculosis is slower than that for Mycobacterium smegmatis. J Bacteriol 2011; 194:956-64. [PMID: 22194452 DOI: 10.1128/jb.06132-11] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Knowledge of the metabolic pathways used by Mycobacterium tuberculosis during infection is important for understanding its nutrient requirements and host adaptation. However, uptake, the first step in the utilization of nutrients, is poorly understood for many essential nutrients, such as inorganic anions. Here, we show that M. tuberculosis utilizes nitrate as the sole nitrogen source, albeit at lower efficiency than asparagine, glutamate, and arginine. The growth of the porin triple mutant M. smegmatis ML16 in media with limiting amounts of nitrate and sulfate as sole nitrogen and sulfur sources, respectively, was delayed compared to that of the wild-type strain. The uptake of sulfate was 40-fold slower than that of the wild-type strain, indicating that the efficient uptake of these anions is dependent on porins. The uptake by M. tuberculosis of sulfate and phosphate was approximately 40- and 10-fold slower than that of M. smegmatis, respectively, which is consistent with the slower growth of M. tuberculosis. However, the uptake of these anions by M. tuberculosis is orders of magnitude faster than diffusion through lipid membranes, indicating that unknown outer membrane proteins are required to facilitate this process.
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313
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The polyketide Pks1 contributes to biofilm formation in Mycobacterium tuberculosis. J Bacteriol 2011; 194:715-21. [PMID: 22123254 DOI: 10.1128/jb.06304-11] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Infections caused by biofilms are abundant and highly persistent, displaying phenotypic resistance to high concentrations of antimicrobials and modulating host immune systems. Tuberculosis (TB), caused by Mycobacterium tuberculosis, shares these qualities with biofilm infections. To identify genetic determinants of biofilm formation in M. tuberculosis, we performed a small-scale transposon screen using an in vitro pellicle biofilm assay. We identified five M. tuberculosis mutants that were reproducibly attenuated for biofilm production relative to that of the parent strain H37Rv. One of the most attenuated mutants is interrupted in pks1, a polyketide synthase gene. When fused with pks15, as in some M. tuberculosis isolates, pks1 contributes to synthesis of the immunomodulatory phenolic glycolipids (PGLs). However, in strains such as H37Rv with split pks15 and pks1 loci, PGL is not produced and pks1 has no previously defined role. We showed that pks1 complementation restores biofilm production independently of the known role of pks1 in PGL synthesis. We also assessed the relationship among biofilm formation, the pks15/1 genotype, and M. tuberculosis phylogeography. A global survey of M. tuberculosis clinical isolates revealed surprising sequence variability in the pks15/1 locus and substantial variation in biofilm phenotypes. Our studies identify novel M. tuberculosis genes that contribute to biofilm production, including pks1. In addition, we find that the ability to make pellicle biofilms is common among M. tuberculosis isolates from throughout the world, suggesting that this trait is relevant to TB propagation or persistence.
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314
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Deletion and overexpression studies on DacB2, a putative low molecular mass penicillin binding protein from Mycobacterium tuberculosis H(37)Rv. Microb Pathog 2011; 52:109-16. [PMID: 22138550 DOI: 10.1016/j.micpath.2011.11.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Revised: 11/14/2011] [Accepted: 11/21/2011] [Indexed: 11/20/2022]
Abstract
Mycobacterium tuberculosis genome encodes several high and low molecular mass penicillin binding proteins. One such low molecular mass protein is DacB2 encoded by open reading frame Rv2911 of M. tuberculosis which is predicted to play a role in peptidoglycan synthesis. In this study we have tried to gain an insight into the role of this accessory cell division protein in mycobacterial physiology by performing overexpression and deletion studies. The overproduction of DacB2 in non-pathogenic, fast growing mycobacterium Mycobacterium smegmatis mc(2)155 resulted in reduced growth, an altered colony morphology, a defect in sliding motility and biofilm formation. A point mutant of DacB2 was made wherein the active site serine residue was mutated to cysteine to abolish the penicillin binding function of protein. The overexpression of mutant protein showed similar results indicating that the effects produced were independent of protein's penicillin binding function. The gene encoding DacB2 was deleted in M. tuberculosis by specialized transduction method. The deletion mutant showed reduced growth in Sauton's medium under acidic and low oxygen availability. The in vitro infection studies with THP-1 cells showed increased intracellular survival of dacB2 mutant compared to parent and complemented strains. The colony morphology and antibiotic sensitivity of mutant and wild-type strains were similar.
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315
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PPE38 modulates the innate immune response and is required for Mycobacterium marinum virulence. Infect Immun 2011; 80:43-54. [PMID: 22038915 DOI: 10.1128/iai.05249-11] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The proline-glutamic acid (PE) and proline-proline-glutamic acid (PPE) family proteins are prevalent in pathogenic mycobacteria and play a diverse role in mycobacterial pathogenesis. While some members have been studied, the function of most PE/PPE proteins remains unknown. In this study, we isolated a transposon-inactivated PPE38 mutant of Mycobacterium marinum and characterized its phenotype. We found that the PPE38 protein is associated with the cell wall and exposed on the cell surface. The inactivation of PPE38 altered the bacterial cell surface properties and led to deficiencies in cord formation, sliding motility, and biofilm formation. The PPE38 mutant was defective in phagocytosis by macrophages and exhibited reduced virulence in adult zebrafish. We also found that PPE38 is involved in the induction of proinflammatory cytokines in infected macrophages. Together, our results indicate that PPE38, a previously uncharacterized protein, plays a role in mycobacterial virulence, presumably by modulating the host innate immune response.
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316
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Ishida S, Arai M, Niikawa H, Kobayashi M. Inhibitory effect of cyclic trihydroxamate siderophore, desferrioxamine E, on the biofilm formation of Mycobacterium species. Biol Pharm Bull 2011; 34:917-20. [PMID: 21628895 DOI: 10.1248/bpb.34.917] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Formation of biofilm in pathogenic bacteria defends them from antibiotics and the immune system of a host's life. Hence, investigation of the molecular mechanisms of biofilm formation and search for new substances counteracting this formation are becoming an attractive research area. In the course of our search for new inhibitors of biofilm formation in Mycobacterium species, we rediscovered a cyclic trihydroxamate siderophore, desferrioxamine E, from the culture of the marine-derived Actinomycete MS67. Desferrioxamine E inhibited biofilm formation of Mycobacterium smegmatis and M. bovis BACILLE de CALMETTE et GUÉRIN (BCG) with minimum inhibitory concentration (MIC) value of 10 µM, while no anti-microbial activity was observed up to 160 µM. Desferrioxamine E was also able to restore the anti-microbial activity of isoniazid against M. smegmatis by inhibiting biofilm formation. Mechanistic analysis of desferrioxamine E suggested that such inhibition might come from the depletion of iron in the medium, which is essential for biofilm formation in Mycobacterium species.
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Affiliation(s)
- Shunsuke Ishida
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
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317
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Orme IM. Development of new vaccines and drugs for TB: limitations and potential strategic errors. Future Microbiol 2011; 6:161-77. [PMID: 21366417 DOI: 10.2217/fmb.10.168] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The concomitant HIV and TB epidemics pose an enormous threat to humanity. After invading the host Mycobacterium tuberculosis initially behaves as an intracellular pathogen, which elicits the emergence of acquired specific resistance in the form of a T-helper-1 T-cell response, and involves the secretion of a myriad of cytokines and chemokines to drive protective immunity and granuloma formation. However, after that, a second phase of the disease process involves survival of bacilli in an extracellular state that is still poorly understood. This article briefly reviews the various strategies currently being used to improve both vaccination and drug therapy of TB, and attempts to make the argument that current viewpoints that dominate [both the field and the current literature] may be seriously flawed. This includes both the choice of new vaccine and drug candidates, and also the ways these are being tested in animal models, which in the opinion of the author run the risk of driving the field backwards rather than forward.
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Affiliation(s)
- Ian M Orme
- Department of Microbiology, Immunology & Pathology, Colorado State University, Colorado, CO 80523, USA.
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318
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Control of bacterial persister cells by Trp/Arg-containing antimicrobial peptides. Appl Environ Microbiol 2011; 77:4878-85. [PMID: 21622798 DOI: 10.1128/aem.02440-10] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Persister cells are dormant phenotypic variants inherent in a bacterial population. They play important roles in chronic infections and present great challenges to therapy due to extremely enhanced tolerance to antibiotics compared to that of normal cells of the same genotype. In this study, we report that cationic membrane-penetrating peptides containing various numbers of arginine and tryptophan repeats are effective in killing persister cells of Escherichia coli HM22, a hyper-persister producer. The activities of three linear peptides [(RW)(n)-NH(2), where n is 2, 3, or 4] and a dendrimeric peptide, (RW)(4D), in killing bacterial persisters were compared. Although the dendrimeric peptide (RW)(4D) requires a lower threshold to kill planktonic persisters, octameric peptide (RW)(4)-NH(2) is the most effective against planktonic persister cells at high concentrations. For example, treatment with 80 μM (RW)(4)-NH(2) for 60 min led to a 99.7% reduction in the number of viable persister cells. The viability of persister cells residing in surface-attached biofilms was also significantly reduced by (RW)(4)-NH(2) and (RW)(4D). These two peptides were also found to significantly enhance the susceptibility of biofilm cells to ofloxacin. The potency of (RW)(4)-NH(2) was further marked by its ability to disperse and kill preformed biofilms harboring high percentages of persister cells. Interestingly, approximately 70% of the dispersed cells were found to have lost their intrinsic tolerance and become susceptible to ampicillin if not killed directly by this peptide. These results are helpful for better understanding the activities of these peptides and may aid in future development of more effective therapies of chronic infections.
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319
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Montamat-Sicotte DJ, Millington KA, Willcox CR, Hingley-Wilson S, Hackforth S, Innes J, Kon OM, Lammas DA, Minnikin DE, Besra GS, Willcox BE, Lalvani A. A mycolic acid-specific CD1-restricted T cell population contributes to acute and memory immune responses in human tuberculosis infection. J Clin Invest 2011; 121:2493-503. [PMID: 21576820 DOI: 10.1172/jci46216] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 03/30/2011] [Indexed: 11/17/2022] Open
Abstract
Current tuberculosis (TB) vaccine strategies are largely aimed at activating conventional T cell responses to mycobacterial protein antigens. However, the lipid-rich cell wall of Mycobacterium tuberculosis (M. tuberculosis) is essential for pathogenicity and provides targets for unconventional T cell recognition. Group 1 CD1-restricted T cells recognize mycobacterial lipids, but their function in human TB is unclear and their ability to establish memory is unknown. Here, we characterized T cells specific for mycolic acid (MA), the predominant mycobacterial cell wall lipid and key virulence factor, in patients with active TB infection. MA-specific T cells were predominant in TB patients at diagnosis, but were absent in uninfected bacillus Calmette-Guérin-vaccinated (BCG-vaccinated) controls. These T cells were CD1b restricted, detectable in blood and disease sites, produced both IFN-γ and IL-2, and exhibited effector and central memory phenotypes. MA-specific responses contracted markedly with declining pathogen burden and, in patients followed longitudinally, exhibited recall expansion upon antigen reencounter in vitro long after successful treatment, indicative of lipid-specific immunological memory. T cell recognition of MA is therefore a significant component of the acute adaptive and memory immune response in TB, suggesting that mycobacterial lipids may be promising targets for improved TB vaccines.
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Affiliation(s)
- Damien J Montamat-Sicotte
- Tuberculosis Research Unit, National Heart and Lung Institute, Imperial College London, London, United Kingdom
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320
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Nikitushkin VD, Demina GR, Kaprelyants AS. Effect of secreted Rpf protein on intracellular contacts in Micrococcus luteus and Mycobacterium smegmatis cultures. Microbiology (Reading) 2011. [DOI: 10.1134/s0026261711020123] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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321
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Fauvart M, De Groote VN, Michiels J. Role of persister cells in chronic infections: clinical relevance and perspectives on anti-persister therapies. J Med Microbiol 2011; 60:699-709. [PMID: 21459912 DOI: 10.1099/jmm.0.030932-0] [Citation(s) in RCA: 298] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Certain infectious diseases caused by pathogenic bacteria are typically chronic in nature. Potentially deadly examples include tuberculosis, caused by Mycobacterium tuberculosis, cystic fibrosis-associated lung infections, primarily caused by Pseudomonas aeruginosa, and candidiasis, caused by the fungal pathogen Candida albicans. A hallmark of this type of illness is the recalcitrance to treatment with antibiotics, even in the face of laboratory tests showing the causative agents to be sensitive to drugs. Recent studies have attributed this treatment failure to the presence of a small, transiently multidrug-tolerant subpopulation of cells, so-called persister cells. Here, we review our current understanding of the role that persisters play in the treatment and outcome of chronic infections. In a second part, we offer a perspective on the development of anti-persister therapies based on genes and mechanisms that have been implicated in persistence over the last decade.
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Affiliation(s)
- Maarten Fauvart
- Centre of Microbial and Plant Genetics, K.U.Leuven, Leuven, Belgium
| | | | - Jan Michiels
- Centre of Microbial and Plant Genetics, K.U.Leuven, Leuven, Belgium
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322
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Hoff DR, Ryan GJ, Driver ER, Ssemakulu CC, De Groote MA, Basaraba RJ, Lenaerts AJ. Location of intra- and extracellular M. tuberculosis populations in lungs of mice and guinea pigs during disease progression and after drug treatment. PLoS One 2011; 6:e17550. [PMID: 21445321 PMCID: PMC3061964 DOI: 10.1371/journal.pone.0017550] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 02/08/2011] [Indexed: 11/18/2022] Open
Abstract
The lengthy treatment regimen for tuberculosis is necessary to eradicate a small sub-population of M. tuberculosis that persists in certain host locations under drug pressure. Limited information is available on persisting bacilli and their location within the lung during disease progression and after drug treatment. Here we provide a comprehensive histopathological and microscopic evaluation to elucidate the location of bacterial populations in animal models for TB drug development.To detect bacilli in tissues, a new combination staining method was optimized using auramine O and rhodamine B for staining acid-fast bacilli, hematoxylin QS for staining tissue and DAPI for staining nuclei. Bacillary location was studied in three animal models used in-house for TB drug evaluations: C57BL/6 mice, immunocompromised GKO mice and guinea pigs. In both mouse models, the bacilli were found primarily intracellularly in inflammatory lesions at most stages of disease, except for late stage GKO mice, which showed significant necrosis and extracellular bacilli after 25 days of infection. This is also the time when hypoxia was initially visualized in GKO mice by 2-piminidazole. In guinea pigs, the majority of bacteria in lungs are extracellular organisms in necrotic lesions and only few, if any, were ever visualized in inflammatory lesions. Following drug treatment in mice a homogenous bacillary reduction across lung granulomas was observed, whereas in guinea pigs the remaining extracellular bacilli persisted in lesions with residual necrosis. In summary, differences in pathogenesis between animal models infected with M. tuberculosis result in various granulomatous lesion types, which affect the location, environment and state of bacilli. The majority of M. tuberculosis bacilli in an advanced disease state were found to be extracellular in necrotic lesions with an acellular rim of residual necrosis. Drug development should be designed to target this bacillary population and should evaluate drug regimens in the appropriate animal models.
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Affiliation(s)
- Donald R. Hoff
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
| | - Gavin J. Ryan
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
| | - Emily R. Driver
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
| | - Cornelius C. Ssemakulu
- Council for Scientific and Industrial Research (CSIR), CSIR Biosciences,
Pretoria, South Africa
| | - Mary A. De Groote
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
| | - Randall J. Basaraba
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
| | - Anne J. Lenaerts
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
- * E-mail:
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323
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Ortíz-Pérez A, Martín-de-Hijas N, Alonso-Rodríguez N, Molina-Manso D, Fernández-Roblas R, Esteban J. Importance of antibiotic penetration in the antimicrobial resistance of biofilm formed by non-pigmented rapidly growing mycobacteria against amikacin, ciprofloxacin and clarithromycin. Enferm Infecc Microbiol Clin 2011; 29:79-84. [DOI: 10.1016/j.eimc.2010.08.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2010] [Revised: 08/24/2010] [Accepted: 08/27/2010] [Indexed: 10/18/2022]
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324
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Sartain MJ, Dick DL, Rithner CD, Crick DC, Belisle JT. Lipidomic analyses of Mycobacterium tuberculosis based on accurate mass measurements and the novel "Mtb LipidDB". J Lipid Res 2011; 52:861-72. [PMID: 21285232 DOI: 10.1194/jlr.m010363] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The cellular envelope of Mycobacterium tuberculosis is highly distinctive and harbors a wealth of unique lipids possessing diverse structural and biological properties. However, the ability to conduct global analyses on the full complement of M. tuberculosis lipids has been missing from the repertoire of tools applied to the study of this important pathogen. We have established methods to detect and identify lipids from all major M. tuberculosis lipid classes through LC/MS lipid profiling. This methodology is based on efficient chromatographic separation and automated ion identification through accurate mass determination and searching of a newly created database (Mtb LipidDB) that contains 2,512 lipid entities. We demonstrate the sensitive detection of molecules representing all known classes of M. tuberculosis lipids from a single crude extract. We also demonstrate the ability of this methodology to identify changes in lipid content in response to cellular growth phases. This work provides a customizable framework and resource to facilitate future studies on mycobacterial lipid biosynthesis and metabolism.
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Affiliation(s)
- Mark J Sartain
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
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325
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Hurdle JG, O'Neill AJ, Chopra I, Lee RE. Targeting bacterial membrane function: an underexploited mechanism for treating persistent infections. Nat Rev Microbiol 2011; 9:62-75. [PMID: 21164535 DOI: 10.1038/nrmicro2474] [Citation(s) in RCA: 583] [Impact Index Per Article: 44.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Persistent infections involving slow-growing or non-growing bacteria are hard to treat with antibiotics that target biosynthetic processes in growing cells. Consequently, there is a need for antimicrobials that can treat infections containing dormant bacteria. In this Review, we discuss the emerging concept that disrupting the bacterial membrane bilayer or proteins that are integral to membrane function (including membrane potential and energy metabolism) in dormant bacteria is a strategy for treating persistent infections. The clinical applicability of these approaches is exemplified by the efficacy of lipoglycopeptides that damage bacterial membranes and of the diarylquinoline TMC207, which inhibits membrane-bound ATP synthase. Despite some drawbacks, membrane-active agents form an important new means of eradicating recalcitrant, non-growing bacteria.
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Affiliation(s)
- Julian G Hurdle
- Department of Biology, University of Texas at Arlington, Arlington, Texas 76019, USA.
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326
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Yadav AB, Singh AK, Verma RK, Mohan M, Agrawal AK, Misra A. The devil’s advocacy: When and why inhaled therapies for tuberculosis may not work. Tuberculosis (Edinb) 2011; 91:65-6. [DOI: 10.1016/j.tube.2010.10.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 10/07/2010] [Accepted: 10/07/2010] [Indexed: 11/26/2022]
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327
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Vander Beken S, Al Dulayymi JR, Naessens T, Koza G, Maza-Iglesias M, Rowles R, Theunissen C, De Medts J, Lanckacker E, Baird MS, Grooten J. Molecular structure of the Mycobacterium tuberculosis virulence factor, mycolic acid, determines the elicited inflammatory pattern. Eur J Immunol 2010; 41:450-60. [PMID: 21268014 DOI: 10.1002/eji.201040719] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 10/20/2010] [Accepted: 11/17/2010] [Indexed: 11/12/2022]
Abstract
Mycolic acids (MAs) occur in the cell wall of Mycobacterium tuberculosis as variable mixtures of different classes and chain lengths. Here, we address the relationship between the structure and its inflammatory function of this virulence factor using single synthetic MA isomers, differing in oxygenation class and cis- versus α-methyl-trans proximal cyclopropane orientation. Analysis of bronchoalveolar inflammation, lung histopathology and alveolar macrophage transcription revealed a strong dependence on these meromycolic chemistries of mouse pulmonary inflammation in response to intratracheal treatments with MAs. Whereas α-MA was inert, oxygenated methoxy- and keto-MA with cis-cyclopropane stereochemistry elicited solid to mild inflammatory responses respectively. In trans-cyclopropane orientation, methoxy-MA partially lost its inflammatory activity and keto-MA exerted anti-inflammatory alternative activation of alveolar macrophages and counteracted cis-methoxy-MA induced airway inflammation. The differential innate immune activities of MAs demonstrated here, dependent on oxygenation class and cis versus α-methyl-trans cyclopropane chemistry, identify a novel means for M. tuberculosis to steer host immune responses during infection.
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Affiliation(s)
- Seppe Vander Beken
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
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328
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Kruh NA, Troudt J, Izzo A, Prenni J, Dobos KM. Portrait of a pathogen: the Mycobacterium tuberculosis proteome in vivo. PLoS One 2010; 5:e13938. [PMID: 21085642 PMCID: PMC2978697 DOI: 10.1371/journal.pone.0013938] [Citation(s) in RCA: 159] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Accepted: 10/07/2010] [Indexed: 12/23/2022] Open
Abstract
Background Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is a facultative intracellular pathogen that can persist within the host. The bacteria are thought to be in a state of reduced replication and metabolism as part of the chronic lung infection. Many in vitro studies have dissected the hypothesized environment within the infected lung, defining the bacterial response to pH, starvation and hypoxia. While these experiments have afforded great insight, the picture remains incomplete. The only way to study the combined effects of these environmental factors and the mycobacterial response is to study the bacterial response in vivo. Methodology/Principal Findings We used the guinea pig model of tuberculosis to examine the bacterial proteome during the early and chronic stages of disease. Lungs were harvested thirty and ninety days after aerosol challenge with Mtb, and analyzed by liquid chromatography-mass spectrometry. To date, in vivo proteomics of the tubercle bacillus has not been described and this work has generated the first large-scale shotgun proteomic data set, comprising over 500 unique protein identifications. Cell wall and cell wall processes, and intermediary metabolism and respiration were the two major functional classes of proteins represented in the infected lung. These classes of proteins displayed the greatest heterogeneity indicating important biological processes for establishment of a productive bacterial infection and its persistence. Proteins necessary for adaptation throughout infection, such as nitrate/nitrite reduction were found at both time points. The PE-PPE protein class, while not well characterized, represented the third most abundant category and showed the most consistent expression during the infection. Conclusions/Significance Cumulatively, the results of this work may provide the basis for rational drug design – identifying numerous Mtb proteins, from essential kinases to products involved in metal regulation and cell wall remodeling, all present throughout the course of infection.
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Affiliation(s)
- Nicole A. Kruh
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Jolynn Troudt
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Angelo Izzo
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Jessica Prenni
- Proteomics and Metabolomics Facility, Colorado State University, Fort Collins, Colorado, United States of America
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Karen M. Dobos
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail:
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329
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Molle V, Gulten G, Vilchèze C, Veyron-Churlet R, Zanella-Cléon I, Sacchettini JC, Jacobs Jr WR, Kremer L. Phosphorylation of InhA inhibits mycolic acid biosynthesis and growth of Mycobacterium tuberculosis. Mol Microbiol 2010; 78:1591-605. [DOI: 10.1111/j.1365-2958.2010.07446.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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330
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Abstract
Bacterial biofilms are structured communities of bacterial cells enclosed in a self-produced polymer matrix that is attached to a surface. Biofilms protect and allow bacteria to survive and thrive in hostile environments. Bacteria within biofilms can withstand host immune responses, and are much less susceptible to antibiotics and disinfectants when compared with their planktonic counterparts. The ability to form biofilms is now considered a universal attribute of micro-organisms. Diseases associated with biofilms require novel methods for their prevention, diagnosis and treatment; this is largely due to the properties of biofilms. Surprisingly, biofilm formation by bacterial pathogens of veterinary importance has received relatively little attention. Here, we review the current knowledge of bacterial biofilms as well as studies performed on animal pathogens.
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331
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Activities of TMC207, rifampin, and pyrazinamide against Mycobacterium tuberculosis infection in guinea pigs. Antimicrob Agents Chemother 2010; 55:124-31. [PMID: 20937788 DOI: 10.1128/aac.00978-10] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The experimental compound TMC207 is showing promise against infections caused by Mycobacterium tuberculosis both in a variety of animal studies and in the field. In this study, we used the guinea pig model, a species that shows several similarities to human tuberculosis, including the hallmark of primary granuloma necrosis, to determine the efficacy of a combination regimen combining TMC207 with rifampin and pyrazinamide. This drug regimen rapidly reduced the bacterial load in the lungs to undetectable levels by 8 weeks of treatment. This reduction was associated with a substantial improvement in lung pathology, but despite this effect areas of residual necrosis still remained. In the draining lymph nodes, however, tissue damage was rapid and not significantly reversed by the drug treatment. Approximately 10 to 11 months after the treatment had ended, the animals began to trigger a Karnovsky scale indicating bacterial regrowth and potential relapse, an event confirmed by the new development of both pulmonary and extrapulmonary granulomatous lesions. Interestingly, a similar rate of relapse was also seen in animals receiving 24 weeks of rifampin, pyrazinamide, and isoniazid standard chemotherapy. These data indicate that TMC207 could be a useful addition to current treatment regimens for tuberculosis.
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332
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Molle V, Kremer L. Division and cell envelope regulation by Ser/Thr phosphorylation: Mycobacterium shows the way. Mol Microbiol 2010; 75:1064-77. [PMID: 20487298 DOI: 10.1111/j.1365-2958.2009.07041.x] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mycobacterium tuberculosis (M. tb) has a complex lifestyle in different environments and involving several developmental stages. The success of M. tb results from its remarkable capacity to survive within the infected host, where it can persist in a non-replicating state for several decades. The survival strategies developed by M. tb are linked to the presence of an unusual cell envelope. However, little is known regarding its capacity to modulate and adapt production of cell wall components in response to environmental conditions or to changes in cell shape and cell division. Signal sensing leading to cellular responses must be tightly regulated to allow survival under variable conditions. Although prokaryotes generally control their signal transduction processes through two-component systems, signalling through Ser/Thr phosphorylation has recently emerged as a critical regulatory mechanism in bacteria. The genome of M. tb possesses a large family of eukaryotic-like Ser/Thr protein kinases (STPKs). The physiological roles of several mycobacterial STPK substrates are connected to cell shape/division and cell envelope biosynthesis. Although these regulatory mechanisms have mostly been studied in Mycobacterium, Ser/Thr phosphorylation appears also to regulate cell division and peptidoglycan synthesis in Corynebacterium and Streptomyces. This review focuses on the proteins which have been identified as STPK substrates and involved in the synthesis of major cell envelope components and cell shape/division in actinomycetes. It is also intended to describe how phosphorylation affects the activity of peptidoglycan biosynthetic enzymes or cell division proteins.
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Affiliation(s)
- Virginie Molle
- Institut de Biologie et Chimie des Protéines (IBCP UMR 5086), CNRS, Université Lyon1, IFR128 BioSciences, Lyon-Gerland, 7 passage du Vercors, 69367 Lyon Cedex 07, France.
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333
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Beukes M, Lemmer Y, Deysel M, Al Dulayymi JR, Baird MS, Koza G, Iglesias MM, Rowles RR, Theunissen C, Grooten J, Toschi G, Roberts VV, Pilcher L, Van Wyngaardt S, Mathebula N, Balogun M, Stoltz AC, Verschoor JA. Structure-function relationships of the antigenicity of mycolic acids in tuberculosis patients. Chem Phys Lipids 2010; 163:800-8. [PMID: 20875402 PMCID: PMC3025329 DOI: 10.1016/j.chemphyslip.2010.09.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 09/14/2010] [Accepted: 09/17/2010] [Indexed: 11/17/2022]
Abstract
Cell wall mycolic acids (MA) from Mycobacterium tuberculosis (M.tb) are CD1b presented antigens that can be used to detect antibodies as surrogate markers of active TB, even in HIV coinfected patients. The use of the complex mixtures of natural MA is complicated by an apparent antibody cross-reactivity with cholesterol. Here firstly we report three recombinant monoclonal scFv antibody fragments in the chicken germ-line antibody repertoire, which demonstrate the possibilities for cross-reactivity: the first recognized both cholesterol and mycolic acids, the second mycolic acids but not cholesterol, and the third cholesterol but not mycolic acids. Secondly, MA structure is experimentally interrogated to try to understand the cross-reactivity. Unique synthetic mycolic acids representative of the three main functional classes show varying antigenicity against human TB patient sera, depending on the functional groups present and on their stereochemistry. Oxygenated (methoxy- and keto-) mycolic acid was found to be more antigenic than alpha-mycolic acids. Synthetic methoxy-mycolic acids were the most antigenic, one containing a trans-cyclopropane apparently being somewhat more antigenic than the natural mixture. Trans-cyclopropane-containing keto- and hydroxy-mycolic acids were also found to be the most antigenic among each of these classes. However, none of the individual synthetic mycolic acids significantly and reproducibly distinguished the pooled serum of TB positive patients from that of TB negative patients better than the natural mixture of MA. This argues against the potential to improve the specificity of serodiagnosis of TB with a defined single synthetic mycolic acid antigen from this set, although sensitivity may be facilitated by using a synthetic methoxy-mycolic acid.
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Affiliation(s)
- Mervyn Beukes
- Department of Biochemistry, University of Pretoria, South Africa
| | - Yolandy Lemmer
- Department of Biochemistry, University of Pretoria, South Africa
| | - Madrey Deysel
- Department of Biochemistry, University of Pretoria, South Africa
| | | | - Mark S. Baird
- School of Chemistry, University of Wales, Bangor, United Kingdom
| | - Gani Koza
- School of Chemistry, University of Wales, Bangor, United Kingdom
| | | | | | | | - Johan Grooten
- Department of Molecular Biomedical Research, Molecular Immunology Unit, Gent University, Belgium
| | - Gianna Toschi
- Department of Biochemistry, University of Pretoria, South Africa
| | | | - Lynne Pilcher
- Department of Chemistry, University of Pretoria, South Africa
| | | | - Nsovo Mathebula
- Department of Chemistry, University of Pretoria, South Africa
| | | | - Anton C. Stoltz
- Department of Infectious Diseases, University of Pretoria, South Africa
| | - Jan A. Verschoor
- Department of Biochemistry, University of Pretoria, South Africa
- Corresponding author. Tel.: +27 124202477; fax: +27 123625302.
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Chandra H, Basir SF, Gupta M, Banerjee N. Glutamine synthetase encoded by glnA-1 is necessary for cell wall resistance and pathogenicity of Mycobacterium bovis. MICROBIOLOGY-SGM 2010; 156:3669-3677. [PMID: 20724386 DOI: 10.1099/mic.0.043828-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Pathogenic strains of mycobacteria produce copious amounts of glutamine synthetase (GS) in the culture medium. The enzyme activity is linked to synthesis of poly-α-l-glutamine (PLG) in the cell walls. This study describes a glnA-1 mutant of Mycobacterium bovis that produces reduced levels of GS. The mutant was able to grow in enriched 7H9 medium without glutamine supplementation. The glnA-1 strain contained no detectable PLG in the cell walls and showed marked sensitivity to different chemical and physical stresses such as lysozyme, SDS and sonication. The sensitivity of the mutant to two antitubercular drugs, rifampicin and d-cycloserine, was also increased. The glnA-1 strain infected THP-1 cells with reduced efficiency and was also attenuated for growth in macrophages. A Mycobacterium smegmatis strain containing the M. bovis glnA-1 gene survived longer in THP-1 cells than the wild-type strain and also produced cell wall-associated PLG. The M. bovis mutant was not able to replicate in the organs of BALB/c mice and was cleared within 4-6 weeks of infection. Disruption of the glnA-1 gene adversely affected biofilm formation on polystyrene surfaces. The results of this study demonstrate that the absence of glnA-1 not only attenuates the pathogen but also affects cell surface properties by altering the cell wall chemistry of the organism via the synthesis of PLG; this may be a target for drug development.
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Affiliation(s)
- Harish Chandra
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Seemi Farhat Basir
- Department of Biosciences, Jamia Millia Islamia, New Delhi 110025, India
| | - Manish Gupta
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Nirupama Banerjee
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India
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335
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Mycobacterial biofilms facilitate horizontal DNA transfer between strains of Mycobacterium smegmatis. J Bacteriol 2010; 192:5134-42. [PMID: 20675473 DOI: 10.1128/jb.00650-10] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Conjugal transfer of chromosomal DNA between strains of Mycobacterium smegmatis occurs by a novel mechanism. In a transposon mutagenesis screen, three transfer-defective insertions were mapped to the lsr2 gene of the donor strain mc(2)155. Because lsr2 encodes a nonspecific DNA-binding protein, mutations of lsr2 give rise to a variety of phenotypes, including an inability to form biofilms. In this study, we show that efficient DNA transfer between strains of M. smegmatis occurs in a mixed biofilm and that the process requires expression of lsr2 in the donor but not in the recipient strain. Testing cells from different strata of standing cultures showed that transfer occurred predominantly at the biofilm air-liquid interface, as other strata containing higher cell densities produced very few transconjugants. These data suggest that the biofilm plays a role beyond mere facilitation of cell-cell contact. Surprisingly, we found that under standard assay conditions the recipient strain does not form a biofilm. Taking these results together, we conclude that for transfer to occur, the recipient strain is actively recruited into the biofilm. In support of this idea, we show that donor and recipient cells are present in almost equal numbers in biofilms that produce transconjugants. Our demonstration of genetic exchange between mycobacteria in a mixed biofilm suggests that conjugation occurs in the environment. Since biofilms are considered to be the predominant natural microhabitat for bacteria, our finding emphasizes the importance of studying biological and physical processes that occur between cells in mixed biofilms.
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336
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Zhu K, Kaprelyants AS, Salina EG, Schuler M, Markx GH. Construction by dielectrophoresis of microbial aggregates for the study of bacterial cell dormancy. BIOMICROFLUIDICS 2010; 4:022810. [PMID: 20697590 PMCID: PMC2917868 DOI: 10.1063/1.3435336] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Accepted: 05/04/2010] [Indexed: 05/11/2023]
Abstract
A study of the effect of aggregate size on the resuscitation of dormant M. smegmatis was conducted by constructing cell aggregates with defined sizes and shapes using dielectrophoresis and monitoring the resuscitation process under controlled laboratorial conditions in a long-term cell feeding system. Differently sized cell aggregates were created on the surface of indium tin oxide coated microelectrodes, their heights and shapes controlled by the strength of the induced electric field and the shape of the microelectrodes. Both two-dimensional (ring-patterned) and three-dimensional cell aggregates were produced. The cell aggregates were maintained under sterile conditions at 37 degrees C for up to 14 days by continuously flushing Sauton's medium through the chamber. Resuscitation of dormant M. smegmatis was evaluated by the production of the fluorescent dye 5-cyano-2,3-ditolyltetrazolium chloride. The results confirm that the resuscitation of dormant M. smegmatis is triggered by the accumulation of a resuscitation promoting factor inside the aggregates by diffusion limitation.
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337
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Ojha AK, Trivelli X, Guerardel Y, Kremer L, Hatfull GF. Enzymatic hydrolysis of trehalose dimycolate releases free mycolic acids during mycobacterial growth in biofilms. J Biol Chem 2010; 285:17380-9. [PMID: 20375425 PMCID: PMC2878501 DOI: 10.1074/jbc.m110.112813] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 04/02/2010] [Indexed: 02/02/2023] Open
Abstract
Mycobacterial species, like other microbes, spontaneously form multicellular drug-tolerant biofilms when grown in vitro in detergent-free liquid media. The structure of Mycobacterium tuberculosis biofilms is formed through genetically programmed pathways and is built upon a large abundance of novel extracellular free mycolic acids (FM), although the mechanism of FM synthesis remained unclear. Here we show that the FM in Mycobacterium smegmatis biofilms is produced through the enzymatic release from constitutively present mycolyl derivatives. One of the precursors for FM is newly synthesized trehalose dimycolate (TDM), which is cleaved by a novel TDM-specific serine esterase, Msmeg_1529. Disruption of Msmeg_1529 leads to undetectable hydrolytic activity, reduced levels of FM in the mutant, and retarded biofilm growth. Furthermore, enzymatic hydrolysis of TDM remains conserved in M. tuberculosis, suggesting the presence of a TDM-specific esterase in this pathogen. Overall, this study provides the first evidence for an enzymatic release of free mycolic acids from cell envelope mycolates during mycobacterial growth.
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Affiliation(s)
- Anil K Ojha
- Department of Infectious Diseases and Microbiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
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338
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Alibaud L, Alahari A, Trivelli X, Ojha AK, Hatfull GF, Guerardel Y, Kremer L. Temperature-dependent regulation of mycolic acid cyclopropanation in saprophytic mycobacteria: role of the Mycobacterium smegmatis 1351 gene (MSMEG_1351) in CIS-cyclopropanation of alpha-mycolates. J Biol Chem 2010; 285:21698-707. [PMID: 20457615 DOI: 10.1074/jbc.m110.125724] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cell envelope is a crucial determinant of virulence and drug resistance in Mycobacterium tuberculosis. Several features of pathogenesis and immunomodulation of host responses are attributable to the structural diversity in cell wall lipids, particularly in the mycolic acids. Structural modification of the alpha-mycolic acid by introduction of cyclopropane rings as catalyzed by the methyltransferase, PcaA, is essential for a lethal, persistent infection and the cording phenotype in M. tuberculosis. Here, we demonstrate the presence of cyclopropanated cell wall mycolates in the nonpathogenic strain Mycobacterium smegmatis and identify MSMEG_1351 as a gene encoding a PcaA homologue. Interestingly, alpha-mycolic acid cyclopropanation was inducible in cultures grown at 25 degrees C. The growth temperature modulation of the cyclopropanating activity was determined by high resolution magic angle spinning NMR analyses on whole cells. In parallel, quantitative reverse transcription-PCR analysis showed that MSMEG_1351 gene expression is up-regulated at 25 degrees C compared with 37 degrees C. An MSMEG_1351 knock-out strain of M. smegmatis, generated by recombineering, exhibited a deficiency in cyclopropanation of alpha-mycolates. The functional equivalence of PcaA and MSMEG_1351 was established by cross-complementation in the MSMEG_1351 knock-out mutant and also in a DeltapcaA strain of Mycobacterium bovis BCG. Overexpression of MSMEG_1351 restored the wild-type mycolic acid profile and the cording phenotype in BCG. Although the biological significance of mycolic acid cyclopropanation in nonpathogenic mycobacteria remains unclear, it likely represents a mechanism of adaptation of cell wall structure and composition to cope with environmental factors.
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Affiliation(s)
- Laeticia Alibaud
- Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Université de Montpellier II et I, CNRS, UMR 5235, Case 107, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France
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339
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Andrews JS, Rolfe SA, Huang WE, Scholes JD, Banwart SA. Biofilm formation in environmental bacteria is influenced by different macromolecules depending on genus and species. Environ Microbiol 2010; 12:2496-507. [PMID: 20406292 DOI: 10.1111/j.1462-2920.2010.02223.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The formation of biofilms by diverse bacteria isolated from contaminated soil and groundwater on model substrata with different surface properties was assessed in a multifactorial screen. Diverse attachment phenotypes were observed as measured by crystal violet dye retention and confocal laser scanning microscopy (CLSM). Bulk measurements of cell hydrophobicity had little predictive ability in determining whether biofilms would develop on hydrophobic or hydrophilic substrata. Therefore selected pairs of bacteria from the genera Rhodococcus, Pseudomonas and Sphingomonas that exhibited different attachment phenotypes were examined in more detail using CLSM and the lipophilic dye, Nile Red. The association of Rhodococcus sp. cell membranes with lipids was shown to influence the attachment properties of these cells, but this approach was not informative for Pseudomonas and Sphingomonas sp. Confocal Raman Microspectroscopy of Rhodococcus biofilms confirmed the importance of lipids in their formation and indicated that in Pseudomonas and Sphingomonas biofilms, nucleic acids and proteins, respectively, were important in identifying the differences in attachment phenotypes of the selected strains. Treatment of biofilms with DNase I confirmed a determining role for nucleic acids as predicted for Pseudomonas. This work demonstrates that the attachment phenotypes of microbes from environmental samples to different substrata varies markedly, a diverse range of macromolecules may be involved and that these differ significantly between genera. A combination of CLSM and Raman spectroscopy distinguished between phenotypes and could be used to identify the key macromolecules involved in cell attachment to surfaces for the specific cases studied.
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Affiliation(s)
- Johanna S Andrews
- The Cell-Mineral Research Centre, Kroto Research Institute, University of Sheffield, Broad Lane, Sheffield S3 7HQ, UK
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340
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Nguyen HT, Wolff KA, Cartabuke RH, Ogwang S, Nguyen L. A lipoprotein modulates activity of the MtrAB two-component system to provide intrinsic multidrug resistance, cytokinetic control and cell wall homeostasis in Mycobacterium. Mol Microbiol 2010; 76:348-64. [PMID: 20233304 DOI: 10.1111/j.1365-2958.2010.07110.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The MtrAB signal transduction system, which participates in multiple cellular processes related to growth and cell wall homeostasis, is the only two-component system known to be essential in Mycobacterium. In a screen for antibiotic resistance determinants in Mycobacterium smegmatis, we identified a multidrug-sensitive mutant with a transposon insertion in lpqB, the gene located immediately downstream of mtrA-mtrB. The lpqB mutant exhibited increased cell-cell aggregation and severe defects in surface motility and biofilm growth. lpqB cells displayed hyphal growth and polyploidism, reminiscent of the morphology of Streptomyces, a related group of filamentous Actinobacteria. Heterologous expression of M. tuberculosis LpqB restored wild-type characteristics to the lpqB mutant. LpqB interacts with the extracellular domain of MtrB, and influences MtrA phosphorylation and promoter activity of dnaA, an MtrA-regulated gene that affects cell division. Furthermore, in trans expression of the non-phosphorylated, inactive form of MtrA in wild-type M. smegmatis resulted in phenotypes similar to those of lpqB deletion, whereas expression of the constitutively active form of MtrA restored wild-type characteristics to the lpqB mutant. These results support a model in which LpqB, MtrB and MtrA form a three-component system that co-ordinates cytokinetic and cell wall homeostatic processes.
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Affiliation(s)
- Hoa T Nguyen
- Department of Molecular Biology and Microbiology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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341
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Veyron-Churlet R, Zanella-Cléon I, Cohen-Gonsaud M, Molle V, Kremer L. Phosphorylation of the Mycobacterium tuberculosis beta-ketoacyl-acyl carrier protein reductase MabA regulates mycolic acid biosynthesis. J Biol Chem 2010; 285:12714-25. [PMID: 20178986 DOI: 10.1074/jbc.m110.105189] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mycolic acids are key cell wall components for the survival, pathogenicity, and antibiotic resistance of the human tubercle bacillus. Although it was thought that Mycobacterium tuberculosis tightly regulates their production to adapt to prevailing environmental conditions, the molecular mechanisms governing mycolic acid biosynthesis remained extremely obscure. Meromycolic acids, the direct precursors of mycolic acids, are synthesized by a type II fatty acid synthase from acyl carrier protein-bound substrates that are extended iteratively, with a reductive cycle in each round of extension, the second step of which is catalyzed by the essential beta-ketoacyl-acyl carrier protein reductase, MabA. In this study, we investigated whether post-translational modifications of MabA might represent a strategy employed by M. tuberculosis to regulate mycolic acid biosynthesis. Indeed, we show here that MabA was efficiently phosphorylated in vitro by several M. tuberculosis Ser/Thr protein kinases, including PknB, as well as in vivo in mycobacteria. Mass spectrometric analyses using LC-ESI/MS/MS and site-directed mutagenesis identified three phosphothreonines, with Thr(191) being the primary phosphor-acceptor. A MabA_T191D mutant, designed to mimic constitutive phosphorylation, exhibited markedly decreased ketoacyl reductase activity compared with the wild-type protein, as well as impaired binding of the NADPH cofactor, as demonstrated by fluorescence spectroscopy. The hypothesis that phosphorylation of Thr(191) alters the enzymatic activity of MabA, and subsequently mycolic acid biosynthesis, was further supported by the fact that constitutive overexpression of the mabA_T191D allele in Mycobacterium bovis BCG strongly impaired mycobacterial growth. Importantly, conditional expression of the phosphomimetic MabA_T191D led to a significant inhibition of de novo biosynthesis of mycolic acids. This study provides the first information on the molecular mechanism(s) involved in mycolic acid regulation through Ser/Thr protein kinase-dependent phosphorylation of a type II fatty acid synthase enzyme.
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Affiliation(s)
- Romain Veyron-Churlet
- Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Université de Montpellier I, CNRS, UMR 5235, case 107, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France
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342
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Evaluation of standard chemotherapy in the guinea pig model of tuberculosis. Antimicrob Agents Chemother 2010; 54:1820-33. [PMID: 20160055 DOI: 10.1128/aac.01521-09] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The purpose of this study was 2-fold. First, we evaluated standard chemotherapy in the guinea pig model of tuberculosis to determine if this animal species could productively be used for this purpose. Second, given the similarities of the pathology of disease in guinea pigs and humans, we wished to evaluate additional parameters, including magnetic resonance imaging, microscopy, and cytokine expression and lymphocyte phenotypes, in response to an infection treated with drug therapy. This study shows that conventional rifampin-isoniazid-pyrazinamide chemotherapy significantly decreased the numbers of the highly virulent Erdman K01 strain of Mycobacterium tuberculosis, with most of the bacilli being eliminated in a month. Despite this result, bacteria could still be detected in the lungs and other tissues for at least another 3 to 4 months. Resolution of the nonnecrotic granulomas in the lungs and lymph nodes could be clearly visualized by magnetic resonance imaging at the macroscopic level. Microscopically, the majority of the pulmonary and extrapulmonary inflammation resolved spontaneously, leaving residual lesions composed of dystrophic calcification and fibrosis marking the site of necrosis of the primary lesion. Residual calcified lesions, which were also associated with pulmonary lymphangitis, contained acid-fast bacilli even following aggressive chemotherapy. The presence of intact extracellular bacilli within these lesions suggests that these could serve as the primary sites of disease reactivation. The chemotherapy reduced the level of T-cell influx into infected tissues and was accompanied by a large and sustained increase in TH1 cytokine expression. Chemotherapy also prevented the emergence in lung tissues of high levels of interleukin-10 and Foxp3-positive cells, known markers of regulatory T cells.
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343
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Abstract
A bacterial colony may develop a small number of cells genetically identical to, but phenotypically different from, other normally growing bacteria. These so-called persister cells keep themselves in a dormant state and thus are insensitive to antibiotic treatment, resulting in serious problems of drug resistance. In this paper, we proposed a novel strategy to 'kill' persister cells by triggering them to switch, in a fast and synchronized way, into normally growing cells that are susceptible to antibiotics. The strategy is based on resonant activation (RA), a well-studied phenomenon in physics where the internal noise of a system can constructively facilitate fast and synchronized barrier crossings. Through stochastic Gilliespie simulation with a generic toggle switch model, we demonstrated that RA exists in the phenotypic switching of a single bacterium. Further, by coupling single cell level and population level simulations, we showed that with RA, one can greatly reduce the time and total amount of antibiotics needed to sterilize a bacterial population. We suggest that resonant activation is a general phenomenon in phenotypic transition, and can find other applications such as cancer therapy.
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Affiliation(s)
- Yan Fu
- Interdisciplinary Program of Genetics, Bioinformatics, and Computational Biology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060, USA
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344
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Microscopic cords, a virulence-related characteristic of Mycobacterium tuberculosis, are also present in nonpathogenic mycobacteria. J Bacteriol 2010; 192:1751-60. [PMID: 20097851 DOI: 10.1128/jb.01485-09] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The aggregation of mycobacterial cells in a definite order, forming microscopic structures that resemble cords, is known as cord formation, or cording, and is considered a virulence factor in the Mycobacterium tuberculosis complex and the species Mycobacterium marinum. In the 1950s, cording was related to a trehalose dimycolate lipid that, consequently, was named the cord factor. However, modern techniques of microbial genetics have revealed that cording can be affected by mutations in genes not directly involved in trehalose dimycolate biosynthesis. Therefore, questions such as "How does mycobacterial cord formation occur?" and "Which molecular factors play a role in cord formation?" remain unanswered. At present, one of the problems in cording studies is the correct interpretation of cording morphology. Using optical microscopy, it is sometimes difficult to distinguish between cording and clumping, which is a general property of mycobacteria due to their hydrophobic surfaces. In this work, we provide a new way to visualize cords in great detail using scanning electron microscopy, and we show the first scanning electron microscopy images of the ultrastructure of mycobacterial cords, making this technique the ideal tool for cording studies. This technique has enabled us to affirm that nonpathogenic mycobacteria also form microscopic cords. Finally, we demonstrate that a strong correlation exists between microscopic cords, rough colonial morphology, and increased persistence of mycobacteria inside macrophages.
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345
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Hunter RL, Armitige L, Jagannath C, Actor JK. TB research at UT-Houston--a review of cord factor: new approaches to drugs, vaccines and the pathogenesis of tuberculosis. Tuberculosis (Edinb) 2009; 89 Suppl 1:S18-25. [PMID: 20006299 PMCID: PMC3682682 DOI: 10.1016/s1472-9792(09)70007-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Tuberculosis remains a major threat as drug resistance continues to increase. Pulmonary tuberculosis in adults is responsible for 80% of clinical cases and nearly 100% of transmission of infection. Unfortunately, since we have no animal models of adult type pulmonary tuberculosis, the most important type of disease remains largely out of reach of modern science and many fundamental questions remain unanswered. This paper reviews research dating back to the 1950's providing compelling evidence that cord factor (trehalose 6,6 dimycolate [TDM]) is essential for understanding tuberculosis. However, the original papers by Bloch and Noll were too far ahead of their time to have immediate impact. We can now recognize that the physical and biologic properties of cord factor are unprecedented in science, especially its ability to switch between two sets of biologic activities with changes in conformation. While TDM remains on organisms, it protects them from killing within macrophages, reduces antibiotic effectiveness and inhibits the stimulation of protective immune responses. If it comes off organisms and associates with lipid, TDM becomes a driver of tissue damage and necrosis. Studies emanating from cord factor research have produced (1) a rationale for improving vaccines, (2) an approach to new drugs that overcome natural resistance to antibiotics, (3) models of caseating granulomas that reproduce multiple manifestations of human tuberculosis. (4) evidence that TDM is a key T cell antigen in destructive lesions of tuberculosis, and (5) a new understanding of the pathology and pathogenesis of postprimary tuberculosis that can guide more informative studies of long standing mysteries of tuberculosis.
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Affiliation(s)
- Robert L Hunter
- University of Texas--Houston Medical School, Department of Pathology and Laboratory, Houston, TX 77030, USA
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346
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Koza G, Rowles R, Theunissen C, Al-Dulayymi JR, Baird MS. The synthesis of single enantiomers of trans-alkene-containing mycolic acids. Tetrahedron Lett 2009. [DOI: 10.1016/j.tetlet.2009.10.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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347
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Al Dulayymi JR, Baird MS, Maza-Iglesias M, Beken SV, Grooten J. The first unique synthetic mycobacterial cord factors. Tetrahedron Lett 2009. [DOI: 10.1016/j.tetlet.2009.03.213] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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348
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Sampson T, Broussard GW, Marinelli LJ, Jacobs-Sera D, Ray M, Ko CC, Russell D, Hendrix RW, Hatfull GF. Mycobacteriophages BPs, Angel and Halo: comparative genomics reveals a novel class of ultra-small mobile genetic elements. MICROBIOLOGY-SGM 2009; 155:2962-2977. [PMID: 19556295 DOI: 10.1099/mic.0.030486-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Mycobacteriophages BPs, Angel and Halo are closely related viruses isolated from Mycobacterium smegmatis, and possess the smallest known mycobacteriophage genomes, 41,901 bp, 42,289 bp and 41,441 bp, respectively. Comparative genome analysis reveals a novel class of ultra-small mobile genetic elements; BPs and Halo each contain an insertion of the proposed mobile elements MPME1 and MPME2, respectively, at different locations, while Angel contains neither. The close similarity of the genomes provides a comparison of the pre- and post-integration sequences, revealing an unusual 6 bp insertion at one end of the element and no target duplication. Nine additional copies of these mobile elements are identified in a variety of different contexts in other mycobacteriophage genomes. In addition, BPs, Angel and Halo have an unusual lysogeny module in which the repressor and integrase genes are closely linked. The attP site is located within the repressor-coding region, such that prophage formation results in expression of a C-terminally truncated, but active, form of the repressor.
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Affiliation(s)
- Timothy Sampson
- Pittsburgh Bacteriophage Institute and Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Gregory W Broussard
- Pittsburgh Bacteriophage Institute and Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Laura J Marinelli
- Pittsburgh Bacteriophage Institute and Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Deborah Jacobs-Sera
- Pittsburgh Bacteriophage Institute and Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Mondira Ray
- Pittsburgh Bacteriophage Institute and Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Ching-Chung Ko
- Pittsburgh Bacteriophage Institute and Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Daniel Russell
- Pittsburgh Bacteriophage Institute and Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Roger W Hendrix
- Pittsburgh Bacteriophage Institute and Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Graham F Hatfull
- Pittsburgh Bacteriophage Institute and Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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349
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Payne K, Sun Q, Sacchettini J, Hatfull GF. Mycobacteriophage Lysin B is a novel mycolylarabinogalactan esterase. Mol Microbiol 2009; 73:367-81. [PMID: 19555454 DOI: 10.1111/j.1365-2958.2009.06775.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Mycobacteriophages encounter a unique problem among phages of Gram-positive bacteria, in that lysis must not only degrade the peptidoglycan layer but also circumvent a mycolic acid-rich outer membrane covalently attached to the arabinogalactan-peptidoglycan complex. Mycobacteriophages accomplish this by producing two lysis enzymes, Lysin A (LysA) that hydrolyses peptidoglycan, and Lysin B (LysB), a novel mycolylarabinogalactan esterase, that cleaves the mycolylarabinogalactan bond to release free mycolic acids. The D29 LysB structure shows an alpha/beta hydrolase organization with a catalytic triad common to cutinases, but which contains an additional four-helix domain implicated in the binding of lipid substrates. Whereas LysA is essential for mycobacterial lysis, a Giles DeltalysB mutant mycobacteriophage is viable, but defective in the normal timing, progression and completion of host cell lysis. We propose that LysB facilitates lysis by compromising the integrity of the mycobacterial outer membrane linkage to the arabinogalactan-peptidoglycan layer.
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Affiliation(s)
- Kimberly Payne
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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350
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Piuri M, Jacobs WR, Hatfull GF. Fluoromycobacteriophages for rapid, specific, and sensitive antibiotic susceptibility testing of Mycobacterium tuberculosis. PLoS One 2009; 4:e4870. [PMID: 19300517 PMCID: PMC2654538 DOI: 10.1371/journal.pone.0004870] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Accepted: 02/16/2009] [Indexed: 11/19/2022] Open
Abstract
Rapid antibiotic susceptibility testing of Mycobacterium tuberculosis is of paramount importance as multiple- and extensively- drug resistant strains of M. tuberculosis emerge and spread. We describe here a virus-based assay in which fluoromycobacteriophages are used to deliver a GFP or ZsYellow fluorescent marker gene to M. tuberculosis, which can then be monitored by fluorescent detection approaches including fluorescent microscopy and flow cytometry. Pre-clinical evaluations show that addition of either Rifampicin or Streptomycin at the time of phage addition obliterates fluorescence in susceptible cells but not in isogenic resistant bacteria enabling drug sensitivity determination in less than 24 hours. Detection requires no substrate addition, fewer than 100 cells can be identified, and resistant bacteria can be detected within mixed populations. Fluorescence withstands fixation by paraformaldehyde providing enhanced biosafety for testing MDR-TB and XDR-TB infections.
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Affiliation(s)
- Mariana Piuri
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - William R. Jacobs
- Howard Hughes Medical Institute, Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Graham F. Hatfull
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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