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Haggerty K, Cantlay S, Young E, Cashbaugh MK, Delatore Iii EF, Schreiber R, Hess H, Komlosi DR, Butler S, Bolon D, Evangelista T, Hager T, Kelly C, Phillips K, Voellinger J, Shanks RMQ, Horzempa J. Identification of an N-terminal tag (580N) that improves the biosynthesis of fluorescent proteins in Francisella tularensis and other Gram-negative bacteria. Mol Cell Probes 2024; 74:101956. [PMID: 38492609 PMCID: PMC11000650 DOI: 10.1016/j.mcp.2024.101956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 03/12/2024] [Accepted: 03/13/2024] [Indexed: 03/18/2024]
Abstract
Utilization of fluorescent proteins is widespread for the study of microbial pathogenesis and host-pathogen interactions. Here, we discovered that linkage of the 36 N-terminal amino acids of FTL_0580 (a hypothetical protein of Francisella tularensis) to fluorescent proteins increases the fluorescence emission of bacteria that express these recombinant fusions. This N-terminal peptide will be referred to as 580N. Western blotting revealed that the linkage of 580N to Emerald Green Fluorescent Protein (EmGFP) in F. tularensis markedly improved detection of this protein. We therefore hypothesized that transcripts containing 580N may be translated more efficiently than those lacking the coding sequence for this leader peptide. In support, expression of emGFPFt that had been codon-optimized for F. tularensis, yielded significantly enhanced fluorescence than its non-optimized counterpart. Furthermore, fusing emGFP with coding sequence for a small N-terminal peptide (Serine-Lysine-Isoleucine-Lysine), which had previously been shown to inhibit ribosomal stalling, produced robust fluorescence when expressed in F. tularensis. These findings support the interpretation that 580N enhances the translation efficiency of fluorescent proteins in F. tularensis. Interestingly, expression of non-optimized 580N-emGFP produced greater fluorescence intensity than any other construct. Structural predictions suggested that RNA secondary structure also may be influencing translation efficiency. When expressed in Escherichia coli and Klebsiella pneumoniae bacteria, 580N-emGFP produced increased green fluorescence compared to untagged emGFP (neither allele was codon optimized for these bacteria). In conclusion, fusing the coding sequence for the 580N leader peptide to recombinant genes might serve as an economical alternative to codon optimization for enhancing protein expression in bacteria.
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Affiliation(s)
- Kristen Haggerty
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Stuart Cantlay
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Emily Young
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Mariah K Cashbaugh
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Elio F Delatore Iii
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Rori Schreiber
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Hayden Hess
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Daniel R Komlosi
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Sarah Butler
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Dalton Bolon
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Theresa Evangelista
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Takoda Hager
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Claire Kelly
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Katherine Phillips
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Jada Voellinger
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA
| | - Robert M Q Shanks
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Joseph Horzempa
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, USA.
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Cantlay S, Garrison NL, Patterson R, Wagner K, Kirk Z, Fan J, Primerano DA, Sullivan MLG, Franks JM, Stolz DB, Horzempa J. Phenotypic and transcriptional characterization of F. tularensis LVS during transition into a viable but non-culturable state. Front Microbiol 2024; 15:1347488. [PMID: 38380104 PMCID: PMC10877056 DOI: 10.3389/fmicb.2024.1347488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 01/15/2024] [Indexed: 02/22/2024] Open
Abstract
Francisella tularensis is a gram-negative, intracellular pathogen which can cause serious, potentially fatal, illness in humans. Species of F. tularensis are found across the Northern Hemisphere and can infect a broad range of host species, including humans. Factors affecting the persistence of F. tularensis in the environment and its epidemiology are not well understood, however, the ability of F. tularensis to enter a viable but non-culturable state (VBNC) may be important. A broad range of bacteria, including many pathogens, have been observed to enter the VBNC state in response to stressful environmental conditions, such as nutrient limitation, osmotic or oxidative stress or low temperature. To investigate the transition into the VBNC state for F. tularensis, we analyzed the attenuated live vaccine strain, F. tularensis LVS grown under standard laboratory conditions. We found that F. tularensis LVS rapidly and spontaneously enters a VBNC state in broth culture at 37°C and that this transition coincides with morphological differentiation of the cells. The VBNC bacteria retained an ability to interact with both murine macrophages and human erythrocytes in in vitro assays and were insensitive to treatment with gentamicin. Finally, we present the first transcriptomic analysis of VBNC F. tularensis, which revealed clear differences in gene expression, and we identify sets of differentially regulated genes which are specific to the VBNC state. Identification of these VBNC specific genes will pave the way for future research aimed at dissecting the molecular mechanisms driving entry into the VBNC state.
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Affiliation(s)
- Stuart Cantlay
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, United States
| | - Nicole L. Garrison
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, United States
| | - Rachelle Patterson
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, United States
| | - Kassey Wagner
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, United States
| | - Zoei Kirk
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, United States
| | - Jun Fan
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV, United States
| | - Donald A. Primerano
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV, United States
| | - Mara L. G. Sullivan
- Department of Cell Biology, Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA, United States
| | - Jonathan M. Franks
- Department of Cell Biology, Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA, United States
| | - Donna B. Stolz
- Department of Cell Biology, Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA, United States
| | - Joseph Horzempa
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV, United States
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Dahlén T, Zhao J, Busch MP, Edgren G. Using routine health-care data to search for unknown transfusion-transmitted disease: a nationwide, agnostic retrospective cohort study. Lancet Digit Health 2024; 6:e105-e113. [PMID: 38278613 DOI: 10.1016/s2589-7500(23)00228-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 10/20/2023] [Accepted: 11/08/2023] [Indexed: 01/28/2024]
Abstract
BACKGROUND Identification and prevention of transfusion-transmitted disease is essential for blood transfusion safety. However, current surveillance systems are largely driven by reports of sentinel events, which is an approach that might be inadequate for identifying transmission of pathogens not known to be transmissible or pathogens with long incubation periods. Using a combination of health-data registers and blood-bank databases, we aimed to perform an agnostic search for potential transfusion-transmitted diseases and to identify unknown threats to the blood supply. METHODS In this nationwide, agnostic retrospective cohort study, we developed a systematic algorithm for performing a phenome-wide search for transfusion-transmitted disease without consideration of any a-priori suspicion of blood-borne transmissibility. We applied this algorithm to a nationwide Swedish transfusion database (SCANDAT-3S) to test for possible transmission of 1155 disease entities based on all relevant diagnostic coding systems in use during the period. We ascertained health outcomes of blood donors and transfusion recipients from the Swedish National Inpatient Register, Swedish Cause of Death Register, and Swedish Cancer Register. Analyses were two-pronged, studying both disease diagnosis concordance between donors and recipients and a possible shared increased disease risk among all recipients of a given donor. For both approaches, we used Cox proportional hazards regression models with time-dependent covariates. Adjustment for multiple comparisons was done using a false discovery rate method. FINDINGS The analyses included data on 1·72 million patients who had received 18·97 million transfusions (red blood cell, plasma, platelet, or whole blood units) between Jan 1, 1968, and Dec 31, 2017, from 1·04 million blood donors. The median follow-up was 4·5 (IQR 0·9-11·4) years for recipients and 18·5 (8·3-26·2) years for donors. We found evidence of transfusion-transmission for 15 diseases, of which 13 were validated using a second conceptually different approach. We identified transmission of viral hepatitis and its complications (eg, oesophageal varices) but also transmission of other conditions (eg, pneumonia of unknown origin). The diseases that could not be validated in this second approach, HIV and abnormal findings in specimens from male genital organs, were not statistically significant after adjustment for multiple testing. The effect sizes were small (close to 1) for other conditions. INTERPRETATION We find no strong evidence of unexpected, widespread transfusion-transmitted disease. This novel approach serves as a proof-of-concept for agnostic, data-driven surveillance for transfusion-transmitted disease using routinely collected blood-bank and health-care data. FUNDING Department of Health and Human Services, US National Heart, Lung, and Blood Institute, US National Institutes of Health, Swedish Research Council and Region Stockholm.
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Affiliation(s)
- Torsten Dahlén
- Department of Medicine, Clinical Epidemiology Division, Karolinska Institutet, Stockholm, Sweden; Department of Haematology, Karolinska University Hospital, Stockholm, Sweden
| | - Jingcheng Zhao
- Department of Medicine, Clinical Epidemiology Division, Karolinska Institutet, Stockholm, Sweden
| | - Michael P Busch
- Vitalant Research Institute, San Francisco, CA, USA; Department of Laboratory Medicine, UCSF, San Francisco, CA, USA
| | - Gustaf Edgren
- Department of Medicine, Clinical Epidemiology Division, Karolinska Institutet, Stockholm, Sweden; Department of Cardiology, Södersjukhuset, Stockholm, Sweden.
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Mlynek KD, Toothman RG, Martinez EE, Qiu J, Richardson JB, Bozue JA. Mutation of wbtJ, a N-formyltransferase involved in O-antigen synthesis, results in biofilm formation, phase variation and attenuation in Francisella tularensis. MICROBIOLOGY (READING, ENGLAND) 2024; 170:001437. [PMID: 38421161 PMCID: PMC10924466 DOI: 10.1099/mic.0.001437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 01/29/2024] [Indexed: 03/02/2024]
Abstract
Two clinically important subspecies, Francisella tularensis subsp. tularensis (type A) and F. tularensis subsp. holarctica (type B) are responsible for most tularaemia cases, but these isolates typically form a weak biofilm under in vitro conditions. Phase variation of the F. tularensis lipopolysaccharide (LPS) has been reported in these subspecies, but the role of variation is unclear as LPS is crucial for virulence. We previously demonstrated that a subpopulation of LPS variants can constitutively form a robust biofilm in vitro, but it is unclear whether virulence was affected. In this study, we show that biofilm-forming variants of both fully virulent F. tularensis subspecies were highly attenuated in the murine tularaemia model by multiple challenge routes. Genomic sequencing was performed on these strains, which revealed that all biofilm-forming variants contained a lesion within the wbtJ gene, a formyltransferase involved in O-antigen synthesis. A ΔwbtJ deletion mutant recapitulated the biofilm, O-antigen and virulence phenotypes observed in natural variants and could be rescued through complementation with a functional wbtJ gene. Since the spontaneously derived biofilm-forming isolates in this study were a subpopulation of natural variants, reversion events to the wbtJ gene were detected that eliminated the phenotypes associated with biofilm variants and restored virulence. These results demonstrate a role for WbtJ in biofilm formation, LPS variation and virulence of F. tularensis.
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Affiliation(s)
- Kevin D. Mlynek
- Bacteriology Division, US ARMY Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
| | - Ronald G. Toothman
- Bacteriology Division, US ARMY Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
| | - Elsie E. Martinez
- Bacteriology Division, US ARMY Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
| | - Ju Qiu
- Regulated Research Administration Division, USAMRIID, Frederick, MD, USA
| | | | - Joel A. Bozue
- Bacteriology Division, US ARMY Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
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Bonnier A, Saha S, Austin A, Saha BK. An Unusual Etiology of Fluorodeoxyglucose Avid Intrathoracic Lymph Nodes. Prague Med Rep 2024; 125:79-86. [PMID: 38380456 DOI: 10.14712/23362936.2024.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024] Open
Abstract
A middle-aged man in his 50s, active smoker, presented to the pulmonary office for lung cancer evaluation. On a low-dose computed tomography for lung cancer screening, he was found to have an 8 mm endobronchial lesion in the right main stem bronchus. A PET-CT revealed no endobronchial lesion, but incidentally, fluorodeoxyglucose (FDG) avidity was present in the right hilar (SUV 13.2) and paratracheal lymph nodes (LNs). He underwent bronchoscopy and EBUS-TBNA of station 7 and 10 R LNs. The fine needle aspiration (FNA) revealed necrotizing epithelioid granuloma. The acid-fast bacilli (AFB) and Grocott methenamine silver (GMS) stains were negative. He had suffered from pneumonic tularemia 13 months ago and immunohistochemical staining for Francisella tularensis on FNA samples at Center for Disease Control and Prevention was negative. The intense positron emission tomography (PET) avidity was attributed to prior tularemic intrathoracic lymphadenitis without active tularemia, a rare occurrence. To the best of our knowledge, PET-positive intrathoracic lymph node beyond one year without evidence of active tularemia has not been previously reported.
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Affiliation(s)
- Alyssa Bonnier
- Department of Critical Care Nursing, Goldfarb School of Nursing, Barnes Jewish College, Saint Louis, USA
| | - Santu Saha
- Department of Medicine, Saha Clinic, Bangladesh
| | - Adam Austin
- Department of Pulmonary, Critical Care and Sleep Medicine, University of Florida, Gainesville, USA
| | - Biplab K Saha
- Department of Pulmonary, Critical Care and Sleep Medicine, University of Florida, Gainesville, USA.
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Köppen K, Fatykhova D, Holland G, Rauch J, Tappe D, Graff M, Rydzewski K, Hocke AC, Hippenstiel S, Heuner K. Ex vivo infection model for Francisella using human lung tissue. Front Cell Infect Microbiol 2023; 13:1224356. [PMID: 37492528 PMCID: PMC10365108 DOI: 10.3389/fcimb.2023.1224356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 06/23/2023] [Indexed: 07/27/2023] Open
Abstract
Introduction Tularemia is mainly caused by Francisella tularensis (Ft) subsp. tularensis (Ftt) and Ft subsp. holarctica (Ftt) in humans and in more than 200 animal species including rabbits and hares. Human clinical manifestations depend on the route of infection and range from flu-like symptoms to severe pneumonia with a mortality rate up to 60% without treatment. So far, only 2D cell culture and animal models are used to study Francisella virulence, but the gained results are transferable to human infections only to a certain extent. Method In this study, we firstly established an ex vivo human lung tissue infection model using different Francisella strains: Ftt Life Vaccine Strain (LVS), Ftt LVS ΔiglC, Ftt human clinical isolate A-660 and a German environmental Francisella species strain W12-1067 (F-W12). Human lung tissue was used to determine the colony forming units and to detect infected cell types by using spectral immunofluorescence and electron microscopy. Chemokine and cytokine levels were measured in culture supernatants. Results Only LVS and A-660 were able to grow within the human lung explants, whereas LVS ΔiglC and F-W12 did not replicate. Using human lung tissue, we observed a greater increase of bacterial load per explant for patient isolate A-660 compared to LVS, whereas a similar replication of both strains was observed in cell culture models with human macrophages. Alveolar macrophages were mainly infected in human lung tissue, but Ftt was also sporadically detected within white blood cells. Although Ftt replicated within lung tissue, an overall low induction of pro-inflammatory cytokines and chemokines was observed. A-660-infected lung explants secreted slightly less of IL-1β, MCP-1, IP-10 and IL-6 compared to Ftt LVS-infected explants, suggesting a more repressed immune response for patient isolate A-660. When LVS and A-660 were used for simultaneous co-infections, only the ex vivo model reflected the less virulent phenotype of LVS, as it was outcompeted by A-660. Conclusion We successfully implemented an ex vivo infection model using human lung tissue for Francisella. The model delivers considerable advantages and is able to discriminate virulent Francisella from less- or non-virulent strains and can be used to investigate the role of specific virulence factors.
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Affiliation(s)
- Kristin Köppen
- Working group “Cellular Interactions of Bacterial Pathogens”, Centre for Biological Threats and Special Pathogens, Highly Pathogenic Microorganisms (ZBS 2), Robert Koch Institute, Berlin, Germany
| | - Diana Fatykhova
- Department of Infectious Diseases, Respiratory Medicine and Critical Care, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Gudrun Holland
- Advanced Light and Electron Microscopy, ZBS 4, Robert Koch Institute, Berlin, Germany
| | - Jessica Rauch
- Research Group Zoonoses, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Dennis Tappe
- Research Group Zoonoses, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Mareike Graff
- Department for General and Thoracic Surgery, DRK Clinics, Berlin, Germany
| | - Kerstin Rydzewski
- Working group “Cellular Interactions of Bacterial Pathogens”, Centre for Biological Threats and Special Pathogens, Highly Pathogenic Microorganisms (ZBS 2), Robert Koch Institute, Berlin, Germany
| | - Andreas C. Hocke
- Department of Infectious Diseases, Respiratory Medicine and Critical Care, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Stefan Hippenstiel
- Department of Infectious Diseases, Respiratory Medicine and Critical Care, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Klaus Heuner
- Working group “Cellular Interactions of Bacterial Pathogens”, Centre for Biological Threats and Special Pathogens, Highly Pathogenic Microorganisms (ZBS 2), Robert Koch Institute, Berlin, Germany
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Cantlay S, Kaftanic C, Horzempa J. PdpC, a secreted effector protein of the type six secretion system, is required for erythrocyte invasion by Francisella tularensis LVS. Front Cell Infect Microbiol 2022; 12:979693. [PMID: 36237421 PMCID: PMC9552824 DOI: 10.3389/fcimb.2022.979693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 09/02/2022] [Indexed: 12/01/2022] Open
Abstract
Francisella tularensis is a gram negative, intracellular pathogen that is the causative agent of the potentially fatal disease, tularemia. During infection, F. tularensis is engulfed by and replicates within host macrophages. Additionally, this bacterium has also been shown to invade human erythrocytes and, in both cases, the Type Six Secretion System (T6SS) is required for these host-pathogen interaction. One T6SS effector protein, PdpC, is important for macrophage infection, playing a role in phagolysosomal escape and intracellular replication. To determine if PdpC also plays a role in erythrocyte invasion, we constructed a pdpC-null mutant in the live vaccine strain, F. tularensis LVS. We show that PdpC is required for invasion of human and sheep erythrocytes during in vitro assays and that reintroduction of a copy of pdpC, in trans, rescues this phenotype. The interaction with human erythrocytes was further characterized using double-immunofluorescence microscopy to show that PdpC is required for attachment of F. tularensis LVS to erythrocytes as well as invasion. To learn more about the role of PdpC in erythrocyte invasion we generated a strain of F. tularensis LVS expressing pdpC-emgfp. PdpC-EmGFP localizes as discrete foci in a subset of F. tularensis LVS cells grown in broth culture and accumulates in erythrocytes during invasion assays. Our results are the first example of a secreted effector protein of the T6SS shown to be involved in erythrocyte invasion and indicate that PdpC is secreted into erythrocytes during invasion.
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Affiliation(s)
| | | | - Joseph Horzempa
- Department of Biological Sciences, West Liberty University, West Liberty, WV, United States
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Roberts LM, Wehrly TD, Leighton I, Hanley P, Lovaglio J, Smith BJ, Bosio CM. Circulating T Cells Are Not Sufficient for Protective Immunity against Virulent Francisella tularensis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2022; 208:1180-1188. [PMID: 35149529 PMCID: PMC8881340 DOI: 10.4049/jimmunol.2100915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 12/23/2021] [Indexed: 11/19/2022]
Abstract
Pulmonary infections elicit a combination of tissue-resident and circulating T cell responses. Understanding the contribution of these anatomically distinct cellular pools in protective immune responses is critical for vaccine development. Francisella tularensis is a highly virulent bacterium capable of causing lethal systemic disease following pulmonary infection for which there is no currently licensed vaccine. Although T cells are required for survival of F. tularensis infection, the relative contribution of tissue-resident and circulating T cells is not completely understood, hampering design of effective, long-lasting vaccines directed against this bacterium. We have previously shown that resident T cells were not sufficient to protect against F. tularensis, suggesting circulating cells may serve a critical role in host defense. To elucidate the role of circulating T cells, we used a model of vaccination and challenge of parabiotic mice. Intranasally infected naive mice conjoined to immune animals had increased numbers of circulating memory T cells and similar splenic bacterial burdens as vaccinated-vaccinated pairs. However, bacterial loads in the lungs of naive parabionts were significantly greater than those observed in vaccinated-vaccinated pairs, but despite early control of F. tularensis replication, all naive-vaccinated pairs succumbed to infection. Together, these data define the specific roles of circulating and resident T cells in defense against infection that is initiated in the pulmonary compartment but ultimately causes disseminated disease. These data also provide evidence for employing vaccination strategies that elicit both pools of T cells for immunity against F. tularensis and may be a common theme for other disseminating bacterial infections.
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Affiliation(s)
- Lydia M Roberts
- Immunity to Pulmonary Pathogens Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Tara D Wehrly
- Immunity to Pulmonary Pathogens Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Ian Leighton
- Immunity to Pulmonary Pathogens Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Patrick Hanley
- Rocky Mountain Veterinary Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Jamie Lovaglio
- Rocky Mountain Veterinary Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Brian J Smith
- Rocky Mountain Veterinary Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Catharine M Bosio
- Immunity to Pulmonary Pathogens Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT; and
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9
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OpiA, a Type Six Secretion System Substrate, Localizes to the Cell Pole and Plays a Role in Bacterial Growth and Viability in Francisella tularensis LVS. J Bacteriol 2020; 202:JB.00048-20. [PMID: 32366588 DOI: 10.1128/jb.00048-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 04/26/2020] [Indexed: 12/19/2022] Open
Abstract
Francisella tularensis is an intracellular pathogen and the causative agent of tularemia. The F. tularensis type six secretion system (T6SS) is required for a number of host-pathogen interactions, including phagolysosomal escape and invasion of erythrocytes. One known effector of the T6SS, OpiA, has recently been shown to be a phosphatidylinositol-3 kinase. To investigate the role of OpiA in erythrocyte invasion, we constructed an opiA-null mutant in the live vaccine strain, F. tularensis LVS. OpiA was not required for erythrocyte invasion; however, deletion of opiA affected growth of F. tularensis LVS in broth cultures in a medium-dependent manner. We also found that opiA influenced cell size, gentamicin sensitivity, bacterial viability, and the lipid content of F. tularensis A fluorescently tagged OpiA (OpiA-emerald-green fluorescent protein [EmGFP]) accumulated at the cell poles of F. tularensis, which is consistent with the location of the T6SS. However, OpiA-EmGFP also exhibited a highly dynamic localization, and this fusion protein was detected in erythrocytes and THP-1 cells in vitro, further supporting that OpiA is secreted. Similar to previous reports with F. novicida, our data demonstrated that opiA had a minimal effect on intracellular replication of F. tularensis in host immune cells in vitro However, THP-1 cells infected with the opiA mutant produced modestly (but significantly) higher levels of the proinflammatory cytokine tumor necrosis factor alpha compared to these host cells infected with wild-type bacteria. We conclude that, in addition to its role in host-pathogen interactions, our results reveal that the function of opiA is central to the biology of F. tularensis bacteria.IMPORTANCE F. tularensis is a pathogenic intracellular pathogen that is of importance for public health and strategic defense. This study characterizes the opiA gene of F. tularensis LVS, an attenuated strain that has been used as a live vaccine but that also shares significant genetic similarity to related Francisella strains that cause human disease. The data presented here provide the first evidence of a T6SS effector protein that affects the physiology of F. tularensis, namely, the growth, cell size, viability, and aminoglycoside resistance of F. tularensis LVS. This study also adds insight into our understanding of OpiA as a determinant of virulence. Finally, the fluorescence fusion constructs presented here will be useful tools for dissecting the role of OpiA in infection.
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Particle and bacteria uptake by Japanese flounder (Paralichthys olivaceus) red blood cells: Size dependence and pathway specificity. Tissue Cell 2019; 61:79-88. [DOI: 10.1016/j.tice.2019.09.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 09/12/2019] [Accepted: 09/13/2019] [Indexed: 12/31/2022]
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Valderrama K, Soto-Dávila M, Segovia C, Vásquez I, Dang M, Santander J. Aeromonas salmonicida infects Atlantic salmon (Salmo salar) erythrocytes. JOURNAL OF FISH DISEASES 2019; 42:1601-1608. [PMID: 31456227 DOI: 10.1111/jfd.13077] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 08/05/2019] [Accepted: 08/06/2019] [Indexed: 06/10/2023]
Abstract
Aeromonas salmonicida subsp. salmonicida (hereafter A. salmonicida) is the aetiological agent of furunculosis in marine and freshwater fish. Once A. salmonicida invade the fish host through skin, gut or gills, it spreads and colonizes the head kidney, liver, spleen and brain. A. salmonicida infects leucocytes and exhibits an extracellular phase in the blood of the host; however, it is unknown whether A. salmonicida have an intraerythrocytic phase. Here, we evaluate whether A. salmonicida infects Atlantic salmon (Salmo salar) erythrocytes in vitro and in vivo. A. salmonicida did not kill primary S. salar erythrocytes, even in the presence of high bacterial loads, but A. salmonicida invaded the S. salar erythrocytes in the absence of evident haemolysis. Naïve Atlantic salmon smolts intraperitoneally infected with A. salmonicida showed bacteraemia 5 days post-infection and the presence of intraerythrocytic A. salmonicida. Our results reveal a novel intraerythrocytic phase during A. salmonicida infection.
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Affiliation(s)
- Katherinne Valderrama
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Ocean Science Centre, Memorial University of Newfoundland, Saint John's, Canada
| | - Manuel Soto-Dávila
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Ocean Science Centre, Memorial University of Newfoundland, Saint John's, Canada
| | - Cristopher Segovia
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Ocean Science Centre, Memorial University of Newfoundland, Saint John's, Canada
| | - Ignacio Vásquez
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Ocean Science Centre, Memorial University of Newfoundland, Saint John's, Canada
| | - My Dang
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Ocean Science Centre, Memorial University of Newfoundland, Saint John's, Canada
| | - Javier Santander
- Marine Microbial Pathogenesis and Vaccinology Laboratory, Department of Ocean Sciences, Ocean Science Centre, Memorial University of Newfoundland, Saint John's, Canada
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12
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Castillo DJ, Rifkin RF, Cowan DA, Potgieter M. The Healthy Human Blood Microbiome: Fact or Fiction? Front Cell Infect Microbiol 2019; 9:148. [PMID: 31139578 PMCID: PMC6519389 DOI: 10.3389/fcimb.2019.00148] [Citation(s) in RCA: 168] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 04/23/2019] [Indexed: 12/21/2022] Open
Abstract
The blood that flows perpetually through our veins and arteries performs numerous functions essential to our survival. Besides distributing oxygen, this vast circulatory system facilitates nutrient transport, deters infection and dispenses heat throughout our bodies. Since human blood has traditionally been considered to be an entirely sterile environment, comprising only blood-cells, platelets and plasma, the detection of microbes in blood was consistently interpreted as an indication of infection. However, although a contentious concept, evidence for the existence of a healthy human blood-microbiome is steadily accumulating. While the origins, identities and functions of these unanticipated micro-organisms remain to be elucidated, information on blood-borne microbial phylogeny is gradually increasing. Given recent advances in microbial-hematology, we review current literature concerning the composition and origin of the human blood-microbiome, focusing on bacteria and their role in the configuration of both the diseased and healthy human blood-microbiomes. Specifically, we explore the ways in which dysbiosis in the supposedly innocuous blood-borne bacterial microbiome may stimulate pathogenesis. In addition to exploring the relationship between blood-borne bacteria and the development of complex disorders, we also address the matter of contamination, citing the influence of contaminants on the interpretation of blood-derived microbial datasets and urging the routine analysis of laboratory controls to ascertain the taxonomic and metabolic characteristics of environmentally-derived contaminant-taxa.
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Affiliation(s)
- Diego J Castillo
- Department of Biochemistry, Genetics and Microbiology, Centre for Microbial Ecology and Genomics, University of Pretoria, Pretoria, South Africa
| | - Riaan F Rifkin
- Department of Biochemistry, Genetics and Microbiology, Centre for Microbial Ecology and Genomics, University of Pretoria, Pretoria, South Africa.,Human Origins and Palaeo Environmental Research Group, Department of Anthropology and Geography, Oxford Brookes University, Oxford, United Kingdom
| | - Don A Cowan
- Department of Biochemistry, Genetics and Microbiology, Centre for Microbial Ecology and Genomics, University of Pretoria, Pretoria, South Africa
| | - Marnie Potgieter
- Department of Biochemistry, Genetics and Microbiology, Centre for Microbial Ecology and Genomics, University of Pretoria, Pretoria, South Africa
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13
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Kell DB, Pretorius E. No effects without causes: the Iron Dysregulation and Dormant Microbes hypothesis for chronic, inflammatory diseases. Biol Rev Camb Philos Soc 2018; 93:1518-1557. [PMID: 29575574 PMCID: PMC6055827 DOI: 10.1111/brv.12407] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 02/12/2018] [Accepted: 02/15/2018] [Indexed: 12/11/2022]
Abstract
Since the successful conquest of many acute, communicable (infectious) diseases through the use of vaccines and antibiotics, the currently most prevalent diseases are chronic and progressive in nature, and are all accompanied by inflammation. These diseases include neurodegenerative (e.g. Alzheimer's, Parkinson's), vascular (e.g. atherosclerosis, pre-eclampsia, type 2 diabetes) and autoimmune (e.g. rheumatoid arthritis and multiple sclerosis) diseases that may appear to have little in common. In fact they all share significant features, in particular chronic inflammation and its attendant inflammatory cytokines. Such effects do not happen without underlying and initially 'external' causes, and it is of interest to seek these causes. Taking a systems approach, we argue that these causes include (i) stress-induced iron dysregulation, and (ii) its ability to awaken dormant, non-replicating microbes with which the host has become infected. Other external causes may be dietary. Such microbes are capable of shedding small, but functionally significant amounts of highly inflammagenic molecules such as lipopolysaccharide and lipoteichoic acid. Sequelae include significant coagulopathies, not least the recently discovered amyloidogenic clotting of blood, leading to cell death and the release of further inflammagens. The extensive evidence discussed here implies, as was found with ulcers, that almost all chronic, infectious diseases do in fact harbour a microbial component. What differs is simply the microbes and the anatomical location from and at which they exert damage. This analysis offers novel avenues for diagnosis and treatment.
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Affiliation(s)
- Douglas B. Kell
- School of ChemistryThe University of Manchester, 131 Princess StreetManchesterLancsM1 7DNU.K.
- The Manchester Institute of BiotechnologyThe University of Manchester, 131 Princess StreetManchesterLancsM1 7DNU.K.
- Department of Physiological SciencesStellenbosch University, Stellenbosch Private Bag X1Matieland7602South Africa
| | - Etheresia Pretorius
- Department of Physiological SciencesStellenbosch University, Stellenbosch Private Bag X1Matieland7602South Africa
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14
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Schmitt DM, Barnes R, Rogerson T, Haught A, Mazzella LK, Ford M, Gilson T, Birch JWM, Sjöstedt A, Reed DS, Franks JM, Stolz DB, Denvir J, Fan J, Rekulapally S, Primerano DA, Horzempa J. The Role and Mechanism of Erythrocyte Invasion by Francisella tularensis. Front Cell Infect Microbiol 2017; 7:173. [PMID: 28536678 PMCID: PMC5423315 DOI: 10.3389/fcimb.2017.00173] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 04/21/2017] [Indexed: 01/06/2023] Open
Abstract
Francisella tularensis is an extremely virulent bacterium that can be transmitted naturally by blood sucking arthropods. During mammalian infection, F. tularensis infects numerous types of host cells, including erythrocytes. As erythrocytes do not undergo phagocytosis or endocytosis, it remains unknown how F. tularensis invades these cells. Furthermore, the consequence of inhabiting the intracellular space of red blood cells (RBCs) has not been determined. Here, we provide evidence indicating that residing within an erythrocyte enhances the ability of F. tularensis to colonize ticks following a blood meal. Erythrocyte residence protected F. tularensis from a low pH environment similar to that of gut cells of a feeding tick. Mechanistic studies revealed that the F. tularensis type VI secretion system (T6SS) was required for erythrocyte invasion as mutation of mglA (a transcriptional regulator of T6SS genes), dotU, or iglC (two genes encoding T6SS machinery) severely diminished bacterial entry into RBCs. Invasion was also inhibited upon treatment of erythrocytes with venom from the Blue-bellied black snake (Pseudechis guttatus), which aggregates spectrin in the cytoskeleton, but not inhibitors of actin polymerization and depolymerization. These data suggest that erythrocyte invasion by F. tularensis is dependent on spectrin utilization which is likely mediated by effectors delivered through the T6SS. Our results begin to elucidate the mechanism of a unique biological process facilitated by F. tularensis to invade erythrocytes, allowing for enhanced colonization of ticks.
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Affiliation(s)
- Deanna M Schmitt
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Rebecca Barnes
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Taylor Rogerson
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Ashley Haught
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Leanne K Mazzella
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Matthew Ford
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Tricia Gilson
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - James W-M Birch
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
| | - Anders Sjöstedt
- Department of Clinical Microbiology, Clinical Bacteriology, and Laboratory for Molecular Infection Medicine Sweden, Umeå UniversityUmeå, Sweden
| | - Douglas S Reed
- Regional Biocontainment Laboratory, Center for Vaccine Research, University of PittsburghPittsburgh, PA, USA
| | - Jonathan M Franks
- Center for Biologic Imaging, University of Pittsburgh School of MedicinePittsburgh, PA, USA
| | - Donna B Stolz
- Center for Biologic Imaging, University of Pittsburgh School of MedicinePittsburgh, PA, USA
| | - James Denvir
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall UniversityHuntington, WV, USA
| | - Jun Fan
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall UniversityHuntington, WV, USA
| | - Swanthana Rekulapally
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall UniversityHuntington, WV, USA
| | - Donald A Primerano
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall UniversityHuntington, WV, USA
| | - Joseph Horzempa
- Department of Natural Sciences and Mathematics, West Liberty UniversityWest Liberty, WV, USA
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15
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Wu X, Ren G, Gunning WT, Weaver DA, Kalinoski AL, Khuder SA, Huntley JF. FmvB: A Francisella tularensis Magnesium-Responsive Outer Membrane Protein that Plays a Role in Virulence. PLoS One 2016; 11:e0160977. [PMID: 27513341 PMCID: PMC4981453 DOI: 10.1371/journal.pone.0160977] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/26/2016] [Indexed: 02/06/2023] Open
Abstract
Francisella tularensis is the causative agent of the lethal disease tularemia. Despite decades of research, little is understood about why F. tularensis is so virulent. Bacterial outer membrane proteins (OMPs) are involved in various virulence processes, including protein secretion, host cell attachment, and intracellular survival. Many pathogenic bacteria require metals for intracellular survival and OMPs often play important roles in metal uptake. Previous studies identified three F. tularensis OMPs that play roles in iron acquisition. In this study, we examined two previously uncharacterized proteins, FTT0267 (named fmvA, for Francisellametal and virulence) and FTT0602c (fmvB), which are homologs of the previously studied F. tularensis iron acquisition genes and are predicted OMPs. To study the potential roles of FmvA and FmvB in metal acquisition and virulence, we first examined fmvA and fmvB expression following pulmonary infection of mice, finding that fmvB was upregulated up to 5-fold during F. tularensis infection of mice. Despite sequence homology to previously-characterized iron-acquisition genes, FmvA and FmvB do not appear to be involved iron uptake, as neither fmvA nor fmvB were upregulated in iron-limiting media and neither ΔfmvA nor ΔfmvB exhibited growth defects in iron limitation. However, when other metals were examined in this study, magnesium-limitation significantly induced fmvB expression, ΔfmvB was found to express significantly higher levels of lipopolysaccharide (LPS) in magnesium-limiting medium, and increased numbers of surface protrusions were observed on ΔfmvB in magnesium-limiting medium, compared to wild-type F. tularensis grown in magnesium-limiting medium. RNA sequencing analysis of ΔfmvB revealed the potential mechanism for increased LPS expression, as LPS synthesis genes kdtA and wbtA were significantly upregulated in ΔfmvB, compared with wild-type F. tularensis. To provide further evidence for the potential role of FmvB in magnesium uptake, we demonstrated that FmvB was outer membrane-localized. Finally, ΔfmvB was found to be attenuated in mice and cytokine analyses revealed that ΔfmvB-infected mice produced lower levels of pro-inflammatory cytokines, including GM-CSF, IL-3, and IL-10, compared with mice infected with wild-type F. tularensis. Taken together, although the function of FmvA remains unknown, FmvB appears to play a role in magnesium uptake and F. tularensis virulence. These results may provide new insights into the importance of magnesium for intracellular pathogens.
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Affiliation(s)
- Xiaojun Wu
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States of America
| | - Guoping Ren
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States of America
| | - William T. Gunning
- Department of Pathology and Electron Microscopy Facility, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States of America
| | - David A. Weaver
- Department of Surgery and Advanced Microscopy and Imaging Center, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States of America
| | - Andrea L. Kalinoski
- Department of Surgery and Advanced Microscopy and Imaging Center, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States of America
| | - Sadik A. Khuder
- Department of Medicine, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States of America
| | - Jason F. Huntley
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States of America
- * E-mail:
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16
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Païssé S, Valle C, Servant F, Courtney M, Burcelin R, Amar J, Lelouvier B. Comprehensive description of blood microbiome from healthy donors assessed by 16S targeted metagenomic sequencing. Transfusion 2016; 56:1138-47. [PMID: 26865079 DOI: 10.1111/trf.13477] [Citation(s) in RCA: 275] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 12/02/2015] [Accepted: 12/03/2015] [Indexed: 12/16/2022]
Abstract
BACKGROUND Recent studies have revealed that the blood of healthy humans is not as sterile as previously supposed. The objective of this study was to provide a comprehensive description of the microbiome present in different fractions of the blood of healthy individuals. STUDY DESIGN AND METHODS The study was conducted in 30 healthy blood donors to the French national blood collection center (Établissement Français du Sang). We have set up a 16S rDNA quantitative polymerase chain reaction assay as well as a 16S targeted metagenomics sequencing pipeline specifically designed to analyze the blood microbiome, which we have used on whole blood as well as on different blood fractions (buffy coat [BC], red blood cells [RBCs], and plasma). RESULTS Most of the blood bacterial DNA is located in the BC (93.74%), and RBCs contain more bacterial DNA (6.23%) than the plasma (0.03%). The distribution of 16S DNA is different for each fraction and spreads over a relatively broad range among donors. At the phylum level, blood fractions contain bacterial DNA mostly from the Proteobacteria phylum (more than 80%) but also from Actinobacteria, Firmicutes, and Bacteroidetes. At deeper taxonomic levels, there are striking differences between the bacterial profiles of the different blood fractions. CONCLUSION We demonstrate that a diversified microbiome exists in healthy blood. This microbiome has most likely an important physiologic role and could be implicated in certain transfusion-transmitted bacterial infections. In this regard, the amount of 16S bacterial DNA or the microbiome profile could be monitored to improve the safety of the blood supply.
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Affiliation(s)
| | | | | | | | | | - Jacques Amar
- Vaiomer SAS, Labège.,Department of Therapeutics, Rangueil Hospital, Toulouse, France
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17
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Loughman K, Hall J, Knowlton S, Sindeldecker D, Gilson T, Schmitt DM, Birch JWM, Gajtka T, Kobe BN, Florjanczyk A, Ingram J, Bakshi CS, Horzempa J. Temperature-Dependent Gentamicin Resistance of Francisella tularensis is Mediated by Uptake Modulation. Front Microbiol 2016; 7:37. [PMID: 26858709 PMCID: PMC4729955 DOI: 10.3389/fmicb.2016.00037] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 01/11/2016] [Indexed: 11/13/2022] Open
Abstract
Gentamicin (Gm) is an aminoglycoside commonly used to treat bacterial infections such as tularemia – the disease caused by Francisella tularensis. In addition to being pathogenic, F. tularensis is found in environmental niches such as soil where this bacterium likely encounters Gm producers (Micromonospora sp.). Here we show that F. tularensis exhibits increased resistance to Gm at ambient temperature (26°C) compared to mammalian body temperature (37°C). To evaluate whether F. tularensis was less permeable to Gm at 26°C, a fluorescent marker [Texas Red (Tr)] was conjugated with Gm, yielding Tr-Gm. Bacteria incubated at 26°C showed reduced fluorescence compared to those at 37°C when exposed to Tr-Gm suggesting that uptake of Gm was reduced at 26°C. Unconjugated Gm competitively inhibited uptake of Tr-Gm, demonstrating that this fluorescent compound was taken up similarly to unconjugated Gm. Lysates of F. tularensis bacteria incubated with Gm at 37°C inhibited the growth of Escherichia coli significantly more than lysates from bacteria incubated at 26°C, further indicating reduced uptake at this lower temperature. Other facultative pathogens (Listeria monocytogenes and Klebsiella pneumoniae) exhibited increased resistance to Gm at 26°C suggesting that the results generated using F. tularensis may be generalizable to diverse bacteria. Regulation of the uptake of antibiotics provides a mechanism by which facultative pathogens survive alongside antibiotic-producing microbes in nature.
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Affiliation(s)
- Kathleen Loughman
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Jesse Hall
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Samantha Knowlton
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Devin Sindeldecker
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Tricia Gilson
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Deanna M Schmitt
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - James W-M Birch
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Tara Gajtka
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Brianna N Kobe
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Aleksandr Florjanczyk
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Jenna Ingram
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Chandra S Bakshi
- Department of Microbiology and Immunology, New York Medical College Valhalla, NY, USA
| | - Joseph Horzempa
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
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18
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Lluch J, Servant F, Païssé S, Valle C, Valière S, Kuchly C, Vilchez G, Donnadieu C, Courtney M, Burcelin R, Amar J, Bouchez O, Lelouvier B. The Characterization of Novel Tissue Microbiota Using an Optimized 16S Metagenomic Sequencing Pipeline. PLoS One 2015; 10:e0142334. [PMID: 26544955 PMCID: PMC4636327 DOI: 10.1371/journal.pone.0142334] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 10/19/2015] [Indexed: 02/07/2023] Open
Abstract
Background Substantial progress in high-throughput metagenomic sequencing methodologies has enabled the characterisation of bacteria from various origins (for example gut and skin). However, the recently-discovered bacterial microbiota present within animal internal tissues has remained unexplored due to technical difficulties associated with these challenging samples. Results We have optimized a specific 16S rDNA-targeted metagenomics sequencing (16S metabarcoding) pipeline based on the Illumina MiSeq technology for the analysis of bacterial DNA in human and animal tissues. This was successfully achieved in various mouse tissues despite the high abundance of eukaryotic DNA and PCR inhibitors in these samples. We extensively tested this pipeline on mock communities, negative controls, positive controls and tissues and demonstrated the presence of novel tissue specific bacterial DNA profiles in a variety of organs (including brain, muscle, adipose tissue, liver and heart). Conclusion The high throughput and excellent reproducibility of the method ensured exhaustive and precise coverage of the 16S rDNA bacterial variants present in mouse tissues. This optimized 16S metagenomic sequencing pipeline will allow the scientific community to catalogue the bacterial DNA profiles of different tissues and will provide a database to analyse host/bacterial interactions in relation to homeostasis and disease.
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Affiliation(s)
- Jérôme Lluch
- Vaiomer SAS, Labège, France
- INRA, GeT-PlaGe, Genotoul, Castanet-Tolosan, France
| | | | | | | | - Sophie Valière
- INRA, GeT-PlaGe, Genotoul, Castanet-Tolosan, France
- INRA, UAR1209, Castanet-Tolosan, France
| | - Claire Kuchly
- INRA, GeT-PlaGe, Genotoul, Castanet-Tolosan, France
- INRA, UAR1209, Castanet-Tolosan, France
| | - Gaëlle Vilchez
- INRA, GeT-PlaGe, Genotoul, Castanet-Tolosan, France
- INRA, UAR1209, Castanet-Tolosan, France
| | - Cécile Donnadieu
- INRA, GeT-PlaGe, Genotoul, Castanet-Tolosan, France
- INRA, UMR1388, GenPhySE, Castanet-Tolosan, France
| | | | | | - Jacques Amar
- INSERM U1048, I2MC, Toulouse, France
- Rangueil Hospital, Department of Therapeutics, Toulouse, France
| | - Olivier Bouchez
- INRA, GeT-PlaGe, Genotoul, Castanet-Tolosan, France
- INRA, UMR1388, GenPhySE, Castanet-Tolosan, France
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19
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Plzakova L, Krocova Z, Kubelkova K, Macela A. Entry of Francisella tularensis into Murine B Cells: The Role of B Cell Receptors and Complement Receptors. PLoS One 2015; 10:e0132571. [PMID: 26161475 PMCID: PMC4498600 DOI: 10.1371/journal.pone.0132571] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 06/16/2015] [Indexed: 01/06/2023] Open
Abstract
Francisella tularensis, the etiological agent of tularemia, is an intracellular pathogen that dominantly infects and proliferates inside phagocytic cells but can be seen also in non-phagocytic cells, including B cells. Although protective immunity is known to be almost exclusively associated with the type 1 pathway of cellular immunity, a significant role of B cells in immune responses already has been demonstrated. Whether their role is associated with antibody-dependent or antibody-independent B cell functions is not yet fully understood. The character of early events during B cell–pathogen interaction may determine the type of B cell response regulating the induction of adaptive immunity. We used fluorescence microscopy and flow cytometry to identify the basic requirements for the entry of F. tularensis into B cells within in vivo and in vitro infection models. Here, we present data showing that Francisella tularensis subsp. holarctica strain LVS significantly infects individual subsets of murine peritoneal B cells early after infection. Depending on a given B cell subset, uptake of Francisella into B cells is mediated by B cell receptors (BCRs) with or without complement receptor CR1/2. However, F. tularensis strain FSC200 ΔiglC and ΔftdsbA deletion mutants are defective in the ability to enter B cells. Once internalized into B cells, F. tularensis LVS intracellular trafficking occurs along the endosomal pathway, albeit without significant multiplication. The results strongly suggest that BCRs alone within the B-1a subset can ensure the internalization process while the BCRs on B-1b and B-2 cells need co-signaling from the co receptor containing CR1/2 to initiate F. tularensis engulfment. In this case, fluidity of the surface cell membrane is a prerequisite for the bacteria’s internalization. The results substantially underline the functional heterogeneity of B cell subsets in relation to F. tularensis.
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Affiliation(s)
- Lenka Plzakova
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
| | - Zuzana Krocova
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
| | - Klara Kubelkova
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
- * E-mail:
| | - Ales Macela
- Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
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20
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Kell D, Potgieter M, Pretorius E. Individuality, phenotypic differentiation, dormancy and 'persistence' in culturable bacterial systems: commonalities shared by environmental, laboratory, and clinical microbiology. F1000Res 2015; 4:179. [PMID: 26629334 PMCID: PMC4642849 DOI: 10.12688/f1000research.6709.2] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/04/2015] [Indexed: 01/28/2023] Open
Abstract
For bacteria, replication mainly involves growth by binary fission. However, in a very great many natural environments there are examples of phenotypically dormant, non-growing cells that do not replicate immediately and that are phenotypically 'nonculturable' on media that normally admit their growth. They thereby evade detection by conventional culture-based methods. Such dormant cells may also be observed in laboratory cultures and in clinical microbiology. They are usually more tolerant to stresses such as antibiotics, and in clinical microbiology they are typically referred to as 'persisters'. Bacterial cultures necessarily share a great deal of relatedness, and inclusive fitness theory implies that there are conceptual evolutionary advantages in trading a variation in growth rate against its mean, equivalent to hedging one's bets. There is much evidence that bacteria exploit this strategy widely. We here bring together data that show the commonality of these phenomena across environmental, laboratory and clinical microbiology. Considerable evidence, using methods similar to those common in environmental microbiology, now suggests that many supposedly non-communicable, chronic and inflammatory diseases are exacerbated (if not indeed largely caused) by the presence of dormant or persistent bacteria (the ability of whose components to cause inflammation is well known). This dormancy (and resuscitation therefrom) often reflects the extent of the availability of free iron. Together, these phenomena can provide a ready explanation for the continuing inflammation common to such chronic diseases and its correlation with iron dysregulation. This implies that measures designed to assess and to inhibit or remove such organisms (or their access to iron) might be of much therapeutic benefit.
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Affiliation(s)
- Douglas Kell
- School of Chemistry and The Manchester Institute of Biotechnology, The University of Manchester, Manchester, Lancashire, M1 7DN, UK
| | - Marnie Potgieter
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia, 0007, South Africa
| | - Etheresia Pretorius
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia, 0007, South Africa
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Kell D, Potgieter M, Pretorius E. Individuality, phenotypic differentiation, dormancy and 'persistence' in culturable bacterial systems: commonalities shared by environmental, laboratory, and clinical microbiology. F1000Res 2015; 4:179. [PMID: 26629334 DOI: 10.12688/f1000research.6709.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/29/2015] [Indexed: 01/28/2023] Open
Abstract
For bacteria, replication mainly involves growth by binary fission. However, in a very great many natural environments there are examples of phenotypically dormant, non-growing cells that do not replicate immediately and that are phenotypically 'nonculturable' on media that normally admit their growth. They thereby evade detection by conventional culture-based methods. Such dormant cells may also be observed in laboratory cultures and in clinical microbiology. They are usually more tolerant to stresses such as antibiotics, and in clinical microbiology they are typically referred to as 'persisters'. Bacterial cultures necessarily share a great deal of relatedness, and inclusive fitness theory implies that there are conceptual evolutionary advantages in trading a variation in growth rate against its mean, equivalent to hedging one's bets. There is much evidence that bacteria exploit this strategy widely. We here bring together data that show the commonality of these phenomena across environmental, laboratory and clinical microbiology. Considerable evidence, using methods similar to those common in environmental microbiology, now suggests that many supposedly non-communicable, chronic and inflammatory diseases are exacerbated (if not indeed largely caused) by the presence of dormant or persistent bacteria (the ability of whose components to cause inflammation is well known). This dormancy (and resuscitation therefrom) often reflects the extent of the availability of free iron. Together, these phenomena can provide a ready explanation for the continuing inflammation common to such chronic diseases and its correlation with iron dysregulation. This implies that measures designed to assess and to inhibit or remove such organisms (or their access to iron) might be of much therapeutic benefit.
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Affiliation(s)
- Douglas Kell
- School of Chemistry and The Manchester Institute of Biotechnology, The University of Manchester, Manchester, Lancashire, M1 7DN, UK
| | - Marnie Potgieter
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia, 0007, South Africa
| | - Etheresia Pretorius
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia, 0007, South Africa
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Potgieter M, Bester J, Kell DB, Pretorius E. The dormant blood microbiome in chronic, inflammatory diseases. FEMS Microbiol Rev 2015; 39:567-91. [PMID: 25940667 PMCID: PMC4487407 DOI: 10.1093/femsre/fuv013] [Citation(s) in RCA: 254] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/02/2015] [Indexed: 02/07/2023] Open
Abstract
Blood in healthy organisms is seen as a ‘sterile’ environment: it lacks proliferating microbes. Dormant or not-immediately-culturable forms are not absent, however, as intracellular dormancy is well established. We highlight here that a great many pathogens can survive in blood and inside erythrocytes. ‘Non-culturability’, reflected by discrepancies between plate counts and total counts, is commonplace in environmental microbiology. It is overcome by improved culturing methods, and we asked how common this would be in blood. A number of recent, sequence-based and ultramicroscopic studies have uncovered an authentic blood microbiome in a number of non-communicable diseases. The chief origin of these microbes is the gut microbiome (especially when it shifts composition to a pathogenic state, known as ‘dysbiosis’). Another source is microbes translocated from the oral cavity. ‘Dysbiosis’ is also used to describe translocation of cells into blood or other tissues. To avoid ambiguity, we here use the term ‘atopobiosis’ for microbes that appear in places other than their normal location. Atopobiosis may contribute to the dynamics of a variety of inflammatory diseases. Overall, it seems that many more chronic, non-communicable, inflammatory diseases may have a microbial component than are presently considered, and may be treatable using bactericidal antibiotics or vaccines. Atopobiosis of microbes (the term describing microbes that appear in places other than where they should be), as well as the products of their metabolism, seems to correlate with, and may contribute to, the dynamics of a variety of inflammatory diseases.
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Affiliation(s)
- Marnie Potgieter
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia 0007, South Africa
| | - Janette Bester
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia 0007, South Africa
| | - Douglas B Kell
- School of Chemistry and The Manchester Institute of Biotechnology, The University of Manchester, 131, Princess St, Manchester M1 7DN, Lancs, UK
| | - Etheresia Pretorius
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Arcadia 0007, South Africa
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Abstract
Brucella spp. are facultative intracellular Gram-negative coccobacilli responsible for brucellosis, a worldwide zoonosis. We observed that Brucella melitensis is able to persist for several weeks in the blood of intraperitoneally infected mice and that transferred blood at any time point tested is able to induce infection in naive recipient mice. Bacterial persistence in the blood is dramatically impaired by specific antibodies induced following Brucella vaccination. In contrast to Bartonella, the type IV secretion system and flagellar expression are not critically required for the persistence of Brucella in blood. ImageStream analysis of blood cells showed that following a brief extracellular phase, Brucella is associated mainly with the erythrocytes. Examination by confocal microscopy and transmission electron microscopy formally demonstrated that B. melitensis is able to invade erythrocytes in vivo. The bacteria do not seem to multiply in erythrocytes and are found free in the cytoplasm. Our results open up new areas for investigation and should serve in the development of novel strategies for the treatment or prophylaxis of brucellosis. Invasion of erythrocytes could potentially protect the bacterial cells from the host's immune response and hamper antibiotic treatment and suggests possible Brucella transmission by bloodsucking insects in nature.
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Minasyan H. Erythrocyte and blood antibacterial defense. Eur J Microbiol Immunol (Bp) 2014; 4:138-43. [PMID: 24883200 DOI: 10.1556/eujmi.4.2014.2.7] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Accepted: 04/10/2014] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED It is an axiom that blood cellular immunity is provided by leukocytes. As to erythrocytes, it is generally accepted that their main function is respiration. Our research provides objective video and photo evidence regarding erythrocyte bactericidal function. Phase-contrast immersion vital microscopy of the blood of patients with bacteremia was performed, and the process of bacteria entrapping and killing by erythrocytes was shot by means of video camera. Video evidence demonstrates that human erythrocytes take active part in blood bactericidal action and can repeatedly engulf and kill bacteria of different species and size. Erythrocytes are extremely important integral part of human blood cellular immunity. COMPARED WITH PHAGOCYTIC LEUKOCYTES, THE ERYTHROCYTES a) are more numerous; b) are able to entrap and kill microorganisms repeatedly without being injured; c) are more resistant to infection and better withstand the attacks of pathogens; d) have longer life span and are produced faster; e) are inauspicious media for proliferation of microbes and do not support replication of chlamidiae, mycoplasmas, rickettsiae, viruses, etc.; and f) are more effective and uncompromised bacterial killers. Blood cellular immunity theory and traditional view regarding the function of erythrocytes in human blood should be revised.
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Schmitt DM, O'Dee DM, Cowan BN, Birch JWM, Mazzella LK, Nau GJ, Horzempa J. The use of resazurin as a novel antimicrobial agent against Francisella tularensis. Front Cell Infect Microbiol 2013; 3:93. [PMID: 24367766 PMCID: PMC3853850 DOI: 10.3389/fcimb.2013.00093] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 11/20/2013] [Indexed: 11/13/2022] Open
Abstract
The highly infectious and deadly pathogen, Francisella tularensis, is classified by the CDC as a Category A bioterrorism agent. Inhalation of a single bacterium results in an acute pneumonia with a 30-60% mortality rate without treatment. Due to the prevalence of antibiotic resistance, there is a strong need for new types of antibacterial drugs. Resazurin is commonly used to measure bacterial and eukaryotic cell viability through its reduction to the fluorescent product resorufin. When tested on various bacterial taxa at the recommended concentration of 44 μM, a potent bactericidal effect was observed against various Francisella and Neisseria species, including the human pathogens type A F. tularensis (Schu S4) and N. gonorrhoeae. As low as 4.4 μM resazurin was sufficient for a 10-fold reduction in F. tularensis growth. In broth culture, resazurin was reduced to resorufin by F. tularensis. Resorufin also suppressed the growth of F. tularensis suggesting that this compound is the biologically active form responsible for decreasing the viability of F. tularensis LVS bacteria. Replication of F. tularensis in primary human macrophages and non-phagocytic cells was abolished following treatment with 44 μM resazurin indicating this compound could be an effective therapy for tularemia in vivo.
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Affiliation(s)
- Deanna M Schmitt
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Dawn M O'Dee
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine Pittsburgh, PA, USA
| | - Brianna N Cowan
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - James W-M Birch
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Leanne K Mazzella
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
| | - Gerard J Nau
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine Pittsburgh, PA, USA ; Department of Medicine - Division of Infectious Diseases, University of Pittsburgh School of Medicine Pittsburgh, PA, USA ; Center for Vaccine Research, University of Pittsburgh School of Medicine Pittsburgh, PA, USA
| | - Joseph Horzempa
- Department of Natural Sciences and Mathematics, West Liberty University West Liberty, WV, USA
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Francisella tularensis intracellular survival: to eat or to die. Microbes Infect 2013; 15:989-997. [PMID: 24513705 DOI: 10.1016/j.micinf.2013.09.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 09/23/2013] [Accepted: 09/23/2013] [Indexed: 12/15/2022]
Abstract
Francisella tularensis is a highly infectious facultative intracellular bacterium causing the zoonotic disease tularemia. Numerous attributes required for F. tularensis intracellular multiplication have been identified recently. However, the mechanisms by which the majority of them interfere with the infected host are still poorly understood. The following review summarizes our current knowledge on the different steps of Francisella intramacrophagic life cycle and expands on the importance of nutrient acquisition.
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Abstract
Francisella tularensis is a highly virulent bacterial pathogen that is easily aerosolized and has a low infectious dose. As an intracellular pathogen, entry of Francisella into host cells is critical for its survival and virulence. However, the initial steps of attachment and internalization of Francisella into host cells are not well characterized, and little is known about bacterial factors that promote these processes. This review highlights our current understanding of Francisella attachment and internalization into host cells. In particular, we emphasize the host cell types Francisella has been shown to interact with, as well as specific receptors and signaling processes involved in the internalization process. This review will shed light on gaps in our current understanding and future areas of investigation.
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Affiliation(s)
- G Brett Moreau
- Department of Microbiology, Immunology, and Cancer Biology; University of Virginia; Charlottesville, VA USA
| | - Barbara J Mann
- Department of Microbiology, Immunology, and Cancer Biology; University of Virginia; Charlottesville, VA USA; Department of Medicine; Division of Infectious Diseases and International Health; University of Virginia; Charlottesville, VA USA
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Consequences of delayed ciprofloxacin and doxycycline treatment regimens against Francisella tularensis airway infection. Antimicrob Agents Chemother 2012; 56:5406-8. [PMID: 22850512 DOI: 10.1128/aac.01104-12] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study examines the efficacy, bacterial load, and humoral response of extensively delayed ciprofloxacin or doxycycline treatments following airway exposure of mice to Francisella tularensis subsp. holarctica (strain LVS) or to the highly virulent F. tularensis subsp. tularensis (strain SchuS4). A delay in onset of both antibiotic treatments allowed the rescue of all LVS-infected animals. However, for animals infected with SchuS4, only ciprofloxacin was efficacious and prolongation of treatment rescued all animals.
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