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Maurin M, Pondérand L, Hennebique A, Pelloux I, Boisset S, Caspar Y. Tularemia treatment: experimental and clinical data. Front Microbiol 2024; 14:1348323. [PMID: 38298538 PMCID: PMC10827922 DOI: 10.3389/fmicb.2023.1348323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Accepted: 12/31/2023] [Indexed: 02/02/2024] Open
Abstract
Tularemia is a zoonosis caused by the Gram negative, facultative intracellular bacterium Francisella tularensis. This disease has multiple clinical presentations according to the route of infection, the virulence of the infecting bacterial strain, and the underlying medical condition of infected persons. Systemic infections (e.g., pneumonic and typhoidal form) and complications are rare but may be life threatening. Most people suffer from local infection (e.g., skin ulcer, conjunctivitis, or pharyngitis) with regional lymphadenopathy, which evolve to suppuration in about 30% of patients and a chronic course of infection. Current treatment recommendations have been established to manage acute infections in the context of a biological threat and do not consider the great variability of clinical situations. This review summarizes literature data on antibiotic efficacy against F. tularensis in vitro, in animal models, and in humans. Empirical treatment with beta-lactams, most macrolides, or anti-tuberculosis agents is usually ineffective. The aminoglycosides gentamicin and streptomycin remain the gold standard for severe infections, and the fluoroquinolones and doxycycline for infections of mild severity, although current data indicate the former are usually more effective. However, the antibiotic treatments reported in the literature are highly variable in their composition and duration depending on the clinical manifestations, the age and health status of the patient, the presence of complications, and the evolution of the disease. Many patients received several antibiotics in combination or successively. Whatever the antibiotic treatment administered, variable but high rates of treatment failures and relapses are still observed, especially in patients treated more then 2-3 weeks after disease onset. In these patients, surgical treatment is often necessary for cure, including drainage or removal of suppurative lymph nodes or other infectious foci. It is currently difficult to establish therapeutic recommendations, particularly due to lack of comparative randomized studies. However, we have attempted to summarize current knowledge through proposals for improving tularemia treatment which will have to be discussed by a group of experts. A major factor in improving the prognosis of patients with tularemia is the early administration of appropriate treatment, which requires better medical knowledge and diagnostic strategy of this disease.
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Affiliation(s)
- Max Maurin
- Centre National de Référence Francisella tularensis, CHU Grenoble Alpes, Grenoble, France
- Université Grenoble Alpes, Translational Innovation in Medicine and Complexity (TIMC), Centre National de la Recherche Scientifique (CNRS), Grenoble, France
| | - Léa Pondérand
- Centre National de Référence Francisella tularensis, CHU Grenoble Alpes, Grenoble, France
- Université Grenoble Alpes, Commissariat à l’énergie atomique (CEA), CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Aurélie Hennebique
- Centre National de Référence Francisella tularensis, CHU Grenoble Alpes, Grenoble, France
- Université Grenoble Alpes, Translational Innovation in Medicine and Complexity (TIMC), Centre National de la Recherche Scientifique (CNRS), Grenoble, France
| | - Isabelle Pelloux
- Centre National de Référence Francisella tularensis, CHU Grenoble Alpes, Grenoble, France
| | - Sandrine Boisset
- Centre National de Référence Francisella tularensis, CHU Grenoble Alpes, Grenoble, France
- Université Grenoble Alpes, Commissariat à l’énergie atomique (CEA), CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Yvan Caspar
- Centre National de Référence Francisella tularensis, CHU Grenoble Alpes, Grenoble, France
- Université Grenoble Alpes, Commissariat à l’énergie atomique (CEA), CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
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Bachert BA, Bozue JA. Peptidoglycan enzymes of Francisella: Roles in cell morphology and pathogenesis, and potential as therapeutic targets. Front Microbiol 2023; 13:1099312. [PMID: 36713212 PMCID: PMC9877522 DOI: 10.3389/fmicb.2022.1099312] [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: 11/15/2022] [Accepted: 12/28/2022] [Indexed: 01/13/2023] Open
Abstract
Peptidoglycan, found within the cell wall of bacteria, is a structure critical for maintaining cell morphology and providing a protective barrier in diverse environments. Peptidoglycan is a remarkably dynamic structure that is constantly remodeled during cell growth and division by various peptidoglycan enzymes. Numerous peptidoglycan enzymes have been characterized from diverse bacteria and are highly sought after as targets for therapeutics. However, very little is known about these enzymes within the biothreat agent Francisella tularensis. As the causative agent of tularemia, F. tularensis is classified as a category A biothreat pathogen, in part due to its low infectious dose and lack of FDA-approved vaccine. Many bacterial species encode multiple peptidoglycan enzymes with redundant functions that allow for compensation if one of the enzymes are inactivated. In contrast, F. tularensis appears to lack this redundancy, indicating peptidoglycan enzymes may be completely essential for growth and could be exploited as targets for medical countermeasures. Indeed, several peptidoglycan enzymes in F. tularensis have been shown to play important roles in cell division, cell morphology, virulence, and modulation of host response. The aim of this review is to summarize findings from the current literature on peptidoglycan enzymes present in Francisella and discuss areas where future research efforts might be directed. We conclude that Francisella harbors a distinct set of peptidoglycan enzymes important for cell growth and virulence and represent potentially valuable targets for the development of novel therapeutics.
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Troha K, Božanić Urbančič N, Korva M, Avšič-Županc T, Battelino S, Vozel D. Vector-Borne Tularemia: A Re-Emerging Cause of Cervical Lymphadenopathy. Trop Med Infect Dis 2022; 7:tropicalmed7080189. [PMID: 36006281 PMCID: PMC9412492 DOI: 10.3390/tropicalmed7080189] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/09/2022] [Accepted: 08/11/2022] [Indexed: 12/16/2022] Open
Abstract
Tularemia is a zoonosis caused by the highly invasive bacterium Francisella tularensis. It is transmitted to humans by direct contact with infected animals or by vectors, such as ticks, mosquitos, and flies. Even though it is well-known as a tick-borne disease, it is usually not immediately recognised after a tick bite. In Slovenia, tularemia is rare, with 1–3 cases reported annually; however, the incidence seems to be increasing. Ulceroglandular tularemia is one of its most common forms, with cervical colliquative lymphadenopathy as a frequent manifestation. The diagnosis of tularemia largely relies on epidemiological information, clinical examination, imaging, and molecular studies. Physicians should consider this disease a differential diagnosis for a neck mass, especially after a tick bite, as its management significantly differs from that of other causes. Tularemia-associated lymphadenitis is treated with antibiotics and surgical drainage of the colliquated lymph nodes. Additionally, tularemia should be noted for its potential use in bioterrorism on behalf of the causative agents’ low infectious dose, possible aerosol formation, no effective vaccine at disposal, and the ability to produce severe disease. This article reviews the recent literature on tularemia and presents a case of an adult male with tick-borne cervical ulceroglandular tularemia.
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Affiliation(s)
- Kaja Troha
- Department of Otorhinolaryngology and Cervicofacial Surgery, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia
| | - Nina Božanić Urbančič
- Department of Otorhinolaryngology and Cervicofacial Surgery, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Miša Korva
- Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Tatjana Avšič-Županc
- Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Saba Battelino
- Department of Otorhinolaryngology and Cervicofacial Surgery, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Domen Vozel
- Department of Otorhinolaryngology and Cervicofacial Surgery, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
- Correspondence:
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Chigwada AD, Mapholi NO, Ogola HJO, Mbizeni S, Masebe TM. Pathogenic and Endosymbiotic Bacteria and Their Associated Antibiotic Resistance Biomarkers in Amblyomma and Hyalomma Ticks Infesting Nguni Cattle (Bos spp.). Pathogens 2022; 11:pathogens11040432. [PMID: 35456107 PMCID: PMC9028808 DOI: 10.3390/pathogens11040432] [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: 03/01/2022] [Revised: 03/27/2022] [Accepted: 03/31/2022] [Indexed: 11/17/2022] Open
Abstract
Deciphering the interactions between ticks and their microbiome is key to revealing new insights on tick biology and pathogen transmission. However, knowledge on tick-borne microbiome diversity and their contribution to drug resistance is scarce in sub–Saharan Africa (SSA), despite endemism of ticks. In this study, high-throughput 16S rRNA amplicon sequencing and PICRUSt predictive function profiling were used to characterize the bacterial community structure and associated antibiotic resistance markers in Amblyomma variegatum, A. hebraeum, and Hyalomma truncatum ticks infesting Nguni cattle (Bos spp.). Twenty-one (seven families and fourteen genera) potentially pathogenic and endosymbiotic bacterial taxa were differentially enriched in two tick genera. In H. truncatum ticks, a higher abundance of Corynebacterium (35.6%), Porphyromonas (14.4%), Anaerococcus (11.1%), Trueperella (3.7%), and Helcococcus (4.7%) was detected. However, Rickettsia (38.6%), Escherichia (7%), and Coxiellaceae (2%) were the major differentially abundant taxa in A. variegatum and A. hebraeum. Further, an abundance of 50 distinct antibiotic resistance biomarkers relating to multidrug resistance (MDR) efflux pumps, drug detoxification enzymes, ribosomal protection proteins, and secretion systems, were inferred in the microbiome. This study provides theoretical insights on the microbiome and associated antibiotic resistance markers, important for the design of effective therapeutic and control decisions for tick-borne diseases in the SSA region.
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Affiliation(s)
- Aubrey Dickson Chigwada
- Department of Life and Consumer Sciences, College of Agriculture and Environmental Sciences, University of South Africa (UNISA), Florida Campus, Roodepoort 1709, South Africa; (A.D.C.); (N.O.M.); (H.J.O.O.); (S.M.)
| | - Ntanganedzeni Olivia Mapholi
- Department of Life and Consumer Sciences, College of Agriculture and Environmental Sciences, University of South Africa (UNISA), Florida Campus, Roodepoort 1709, South Africa; (A.D.C.); (N.O.M.); (H.J.O.O.); (S.M.)
| | - Henry Joseph Oduor Ogola
- Department of Life and Consumer Sciences, College of Agriculture and Environmental Sciences, University of South Africa (UNISA), Florida Campus, Roodepoort 1709, South Africa; (A.D.C.); (N.O.M.); (H.J.O.O.); (S.M.)
- School of Agricultural and Food Sciences, Jaramogi Oginga Odinga University of Science and Technology, Bondo P.O. Box 210-40601, Kenya
| | - Sikhumbuzo Mbizeni
- Department of Life and Consumer Sciences, College of Agriculture and Environmental Sciences, University of South Africa (UNISA), Florida Campus, Roodepoort 1709, South Africa; (A.D.C.); (N.O.M.); (H.J.O.O.); (S.M.)
| | - Tracy Madimabi Masebe
- Department of Life and Consumer Sciences, College of Agriculture and Environmental Sciences, University of South Africa (UNISA), Florida Campus, Roodepoort 1709, South Africa; (A.D.C.); (N.O.M.); (H.J.O.O.); (S.M.)
- Correspondence: ; Tel.: +27-11-471-2268
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Rotem S, Steinberger-Levy I, Israeli O, Zahavy E, Aloni-Grinstein R. Beating the Bio-Terror Threat with Rapid Antimicrobial Susceptibility Testing. Microorganisms 2021; 9:1535. [PMID: 34361970 PMCID: PMC8304332 DOI: 10.3390/microorganisms9071535] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 07/15/2021] [Accepted: 07/16/2021] [Indexed: 11/16/2022] Open
Abstract
A bioterror event using an infectious bacterium may lead to catastrophic outcomes involving morbidity and mortality as well as social and psychological stress. Moreover, a bioterror event using an antibiotic resistance engineered bacterial agent may raise additional concerns. Thus, preparedness is essential to preclude and control the dissemination of the bacterial agent as well as to appropriately and promptly treat potentially exposed individuals or patients. Rates of morbidity, death, and social anxiety can be drastically reduced if the rapid delivery of antimicrobial agents for post-exposure prophylaxis and treatment is initiated as soon as possible. Availability of rapid antibiotic susceptibility tests that may provide key recommendations to targeted antibiotic treatment is mandatory, yet, such tests are only at the development stage. In this review, we describe the recently published rapid antibiotic susceptibility tests implemented on bioterror bacterial agents and discuss their assimilation in clinical and environmental samples.
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Affiliation(s)
| | | | | | | | - Ronit Aloni-Grinstein
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona 74100, Israel; (S.R.); (I.S.-L.); (O.I.); (E.Z.)
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Kassinger SJ, van Hoek ML. Genetic Determinants of Antibiotic Resistance in Francisella. Front Microbiol 2021; 12:644855. [PMID: 34054749 PMCID: PMC8149597 DOI: 10.3389/fmicb.2021.644855] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/25/2021] [Indexed: 12/21/2022] Open
Abstract
Tularemia, caused by Francisella tularensis, is endemic to the northern hemisphere. This zoonotic organism has historically been developed into a biological weapon. For this Tier 1, Category A select agent, it is important to expand our understanding of its mechanisms of antibiotic resistance (AMR). Francisella is unlike many Gram-negative organisms in that it does not have significant plasmid mobility, and does not express AMR mechanisms on plasmids; thus plasmid-mediated resistance does not occur naturally. It is possible to artificially introduce plasmids with AMR markers for cloning and gene expression purposes. In this review, we survey both the experimental research on AMR in Francisella and bioinformatic databases which contain genomic and proteomic data. We explore both the genetic determinants of intrinsic AMR and naturally acquired or engineered antimicrobial resistance as well as phenotypic resistance in Francisella. Herein we survey resistance to beta-lactams, monobactams, carbapenems, aminoglycosides, tetracycline, polymyxins, macrolides, rifampin, fosmidomycin, and fluoroquinolones. We also highlight research about the phenotypic AMR difference between planktonic and biofilm Francisella. We discuss newly developed methods of testing antibiotics against Francisella which involve the intracellular nature of Francisella infection and may better reflect the eventual clinical outcomes for new antibiotic compounds. Understanding the genetically encoded determinants of AMR in Francisella is key to optimizing the treatment of patients and potentially developing new antimicrobials for this dangerous intracellular pathogen.
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Affiliation(s)
| | - Monique L. van Hoek
- School of Systems Biology, George Mason University, Manassas, VA, United States
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Travis BA, Ramsey KM, Prezioso SM, Tallo T, Wandzilak JM, Hsu A, Borgnia M, Bartesaghi A, Dove SL, Brennan RG, Schumacher MA. Structural Basis for Virulence Activation of Francisella tularensis. Mol Cell 2021; 81:139-152.e10. [PMID: 33217319 PMCID: PMC7959165 DOI: 10.1016/j.molcel.2020.10.035] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 09/25/2020] [Accepted: 10/22/2020] [Indexed: 01/25/2023]
Abstract
The bacterium Francisella tularensis (Ft) is one of the most infectious agents known. Ft virulence is controlled by a unique combination of transcription regulators: the MglA-SspA heterodimer, PigR, and the stress signal, ppGpp. MglA-SspA assembles with the σ70-associated RNAP holoenzyme (RNAPσ70), forming a virulence-specialized polymerase. These factors activate Francisella pathogenicity island (FPI) gene expression, which is required for virulence, but the mechanism is unknown. Here we report FtRNAPσ70-promoter-DNA, FtRNAPσ70-(MglA-SspA)-promoter DNA, and FtRNAPσ70-(MglA-SspA)-ppGpp-PigR-promoter DNA cryo-EM structures. Structural and genetic analyses show MglA-SspA facilitates σ70 binding to DNA to regulate virulence and virulence-enhancing genes. Our Escherichia coli RNAPσ70-homodimeric EcSspA structure suggests this is a general SspA-transcription regulation mechanism. Strikingly, our FtRNAPσ70-(MglA-SspA)-ppGpp-PigR-DNA structure reveals ppGpp binding to MglA-SspA tethers PigR to promoters. PigR in turn recruits FtRNAP αCTDs to DNA UP elements. Thus, these studies unveil a unique mechanism for Ft pathogenesis involving a virulence-specialized RNAP that employs two (MglA-SspA)-based strategies to activate virulence genes.
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Affiliation(s)
- Brady A Travis
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA
| | - Kathryn M Ramsey
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Department of Cell and Molecular Biology and Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, RI 02881, USA
| | - Samantha M Prezioso
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Thomas Tallo
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Jamie M Wandzilak
- Department of Cell and Molecular Biology and Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, RI 02881, USA
| | - Allen Hsu
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, USA
| | - Mario Borgnia
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, USA
| | - Alberto Bartesaghi
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA; Department of Computer Science, Duke University, Durham, NC 27708, USA
| | - Simon L Dove
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | - Richard G Brennan
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA.
| | - Maria A Schumacher
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA.
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Duplantier AJ, Shurtleff AC, Miller C, Chiang CY, Panchal RG, Sunay M. Combating biothreat pathogens: ongoing efforts for countermeasure development and unique challenges. DRUG DISCOVERY TARGETING DRUG-RESISTANT BACTERIA 2020. [PMCID: PMC7258707 DOI: 10.1016/b978-0-12-818480-6.00007-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Research to discover and develop antibacterial and antiviral drugs with potent activity against pathogens of biothreat concern presents unique methodological and process-driven challenges. Herein, we review laboratory approaches for finding new antibodies, antibiotics, and antiviral molecules for pathogens of biothreat concern. Using high-throughput screening techniques, molecules that directly inhibit a pathogen’s entry, replication, or growth can be identified. Alternatively, molecules that target host proteins can be interesting targets for development when countering biothreat pathogens, due to the modulation of the host immune response or targeting proteins that interfere with the pathways required by the pathogen for replication. Monoclonal and cocktail antibody therapies approved by the Food and Drug Administration for countering anthrax and under development for treatment of Ebola virus infection are discussed. A comprehensive tabular review of current in vitro, in vivo, pharmacokinetic and efficacy datasets has been presented for biothreat pathogens of greatest concern. Finally, clinical trials and animal rule or traditional drug approval pathways are also reviewed. Opinions; interpretations; conclusions; and recommendations are those of the authors and are not necessarily endorsed by the US Army.
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The D-alanyl-d-alanine carboxypeptidase enzyme is essential for virulence in the Schu S4 strain of Francisella tularensis and a dacD mutant is able to provide protection against a pneumonic challenge. Microb Pathog 2019; 137:103742. [PMID: 31513897 DOI: 10.1016/j.micpath.2019.103742] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 07/22/2019] [Accepted: 09/09/2019] [Indexed: 01/04/2023]
Abstract
Low molecular mass penicillin binding proteins (LMM PBP) are bacterial enzymes involved in the final steps of peptidoglycan biosynthesis. In Escherichia coli, most LMM PBP exhibit dd-carboxypeptidase activity, are not essential for growth in routine laboratory media, and contributions to virulent phenotypes remain largely unknown. The Francisella tularensis Schu S4 genome harbors the dacD gene (FTT_1029), which encodes a LMM PBP with homology to PBP6b of E. coli. Disruption of this locus in the fully virulent Schu S4 strain resulted in a mutant that could not grow in Chamberlain's Defined Medium and exhibited severe morphological defects. Further characterization studies demonstrated that the growth defects of the dacD mutant were pH-dependent, and could be partially restored by growth at neutral pH or fully restored by genetic complementation. Infection of murine macrophage-like cells showed that the Schu S4 dacD mutant is capable of intracellular replication. However, this mutant was attenuated in BALB/c mice following intranasal challenge (LD50 = 603 CFU) as compared to mice challenged with the parent (LD50 = 1 CFU) or complemented strain (LD50 = 1 CFU). Additionally, mice that survived infection with the dacD mutant showed significant protection against subsequent challenge with the parent strain. Collectively, these results indicate that the DacD protein of F. tularensis is essential for growth in low pH environments and virulence in vivo. These results also suggest that a PBP mutant could serve as the basis of a novel, live attenuated vaccine strain.
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Halfon Y, Matzov D, Eyal Z, Bashan A, Zimmerman E, Kjeldgaard J, Ingmer H, Yonath A. Exit tunnel modulation as resistance mechanism of S. aureus erythromycin resistant mutant. Sci Rep 2019; 9:11460. [PMID: 31391518 PMCID: PMC6685948 DOI: 10.1038/s41598-019-48019-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 07/25/2019] [Indexed: 12/16/2022] Open
Abstract
The clinical use of the antibiotic erythromycin (ery) is hampered owing to the spread of resistance genes that are mostly mutating rRNA around the ery binding site at the entrance to the protein exit tunnel. Additional effective resistance mechanisms include deletion or insertion mutations in ribosomal protein uL22, which lead to alterations of the exit tunnel shape, located 16 Å away from the drug's binding site. We determined the cryo-EM structures of the Staphylococcus aureus 70S ribosome, and its ery bound complex with a two amino acid deletion mutation in its ß hairpin loop, which grants the bacteria resistance to ery. The structures reveal that, although the binding of ery is stable, the movement of the flexible shorter uL22 loop towards the tunnel wall creates a wider path for nascent proteins, thus enabling bypass of the barrier formed by the drug. Moreover, upon drug binding, the tunnel widens further.
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Affiliation(s)
- Yehuda Halfon
- The Weizmann Institute of Science, The Department of structural biology, Rehovot, 7610001, Israel
| | - Donna Matzov
- The Weizmann Institute of Science, The Department of structural biology, Rehovot, 7610001, Israel
| | - Zohar Eyal
- The Weizmann Institute of Science, The Department of structural biology, Rehovot, 7610001, Israel
| | - Anat Bashan
- The Weizmann Institute of Science, The Department of structural biology, Rehovot, 7610001, Israel
| | - Ella Zimmerman
- The Weizmann Institute of Science, The Department of structural biology, Rehovot, 7610001, Israel
| | - Jette Kjeldgaard
- National Food Institute, Technical University of Denmark, Kemitorvet, DK-2800, Kgs, Lyngby, Denmark
| | - Hanne Ingmer
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 1870, Frederiksberg, Denmark
| | - Ada Yonath
- The Weizmann Institute of Science, The Department of structural biology, Rehovot, 7610001, Israel.
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11
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Bachert BA, Biryukov SS, Chua J, Rodriguez SA, Toothman RG, Cote CK, Klimko CP, Hunter M, Shoe JL, Williams JA, Kuehl KA, Biot FV, Bozue JA. A Francisella novicida Mutant, Lacking the Soluble Lytic Transglycosylase Slt, Exhibits Defects in Both Growth and Virulence. Front Microbiol 2019; 10:1343. [PMID: 31258523 PMCID: PMC6587636 DOI: 10.3389/fmicb.2019.01343] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 05/29/2019] [Indexed: 01/28/2023] Open
Abstract
Francisella tularensis is the causative agent of tularemia and has gained recent interest as it poses a significant biothreat risk. F. novicida is commonly used as a laboratory surrogate for tularemia research due to genetic similarity and susceptibility of mice to infection. Currently, there is no FDA-approved tularemia vaccine, and identifying therapeutic targets remains a critical gap in strategies for combating this pathogen. Here, we investigate the soluble lytic transglycosylase or Slt in F. novicida, which belongs to a class of peptidoglycan-modifying enzymes known to be involved in cell division. We assess the role of Slt in biology and virulence of the organism as well as the vaccine potential of the slt mutant. We show that the F. novicida slt mutant has a significant growth defect in acidic pH conditions. Further microscopic analysis revealed significantly altered cell morphology compared to wild-type, including larger cell size, extensive membrane protrusions, and cell clumping and fusion, which was partially restored by growth in neutral pH or genetic complementation. Viability of the mutant was also significantly decreased during growth in acidic medium, but not at neutral pH. Furthermore, the slt mutant exhibited significant attenuation in a murine model of intranasal infection and virulence could be restored by genetic complementation. Moreover, we could protect mice using the slt mutant as a live vaccine strain against challenge with the parent strain; however, we were not able to protect against challenge with the fully virulent F. tularensis Schu S4 strain. These studies demonstrate a critical role for the Slt enzyme in maintaining proper cell division and morphology in acidic conditions, as well as replication and virulence in vivo. Our results suggest that although the current vaccination strategy with F. novicida slt mutant would not protect against Schu S4 challenges, the Slt enzyme could be an ideal target for future therapeutic development.
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Affiliation(s)
- Beth A Bachert
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Sergei S Biryukov
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Jennifer Chua
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Sabrina A Rodriguez
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Ronald G Toothman
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Christopher K Cote
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Christopher P Klimko
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Melissa Hunter
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Jennifer L Shoe
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Janice A Williams
- Pathology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Kathleen A Kuehl
- Pathology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
| | - Fabrice V Biot
- Unité de Bactériologie/UMR_MD1, Département de Biologie des Agents Transmissibles, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France
| | - Joel A Bozue
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, United States
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12
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Tomaso H, Hotzel H, Otto P, Myrtennäs K, Forsman M. Antibiotic susceptibility in vitro of Francisella tularensis subsp. holarctica isolates from Germany. J Antimicrob Chemother 2018; 72:2539-2543. [PMID: 28605439 DOI: 10.1093/jac/dkx182] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 05/15/2017] [Indexed: 11/13/2022] Open
Abstract
Background Tularaemia is a zoonotic disease caused by the bacterium Francisella tularensis. In Germany, the disease is still rare (e.g. 34 human cases reported in 2015). There is a lack of data about the susceptibility of F. tularensis strains to antibiotics, because many cases are diagnosed using serological assays only. Objectives The antibiotic susceptibility in vitro of F. tularensis subsp. holarctica strains isolated in Germany was assessed to determine whether the currently recommended empirical therapy is still adequate. Methods A total of 128 F. tularensis strains were investigated that were collected between 2005 and 2014 in Germany from wild animals, ticks and humans. All isolates were genotyped using real-time PCR assays targeting canonical SNPs, and antibiotic susceptibility was tested using MIC test strips on agar plates. MIC values were interpreted using CLSI breakpoints. Results The strains were susceptible to antibiotics commonly recommended for tularaemia therapy, i.e. aminoglycosides (MIC90 values: gentamicin 1 mg/L; streptomycin 4.0 mg/L), tetracyclines (MIC90 values: tetracycline 0.5 mg/L; doxycycline 1.5 mg/L) and quinolones (MIC90 value: ciprofloxacin 0.064 mg/L). Chloramphenicol (MIC90 value: 3.0 mg/L) may be of value in treatment of tularaemia meningitis. Ninety-four isolates were susceptible to erythromycin, which defines biovar I (genotypes B.4 and B.6); 34 were resistant (biovar II; genotype B.12). Conclusions The F. tularensis isolates investigated in this study showed the typical antibiotic susceptibility pattern that was previously observed in other countries. Therefore, recommendations for empirical antibiotic therapy of tularaemia can remain unchanged. However, antibiotic susceptibility testing of clinical isolates should be performed whenever possible.
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Affiliation(s)
- Herbert Tomaso
- Institute of Bacterial Infections and Zoonoses, Friedrich-Loeffler-Institut (Federal Research Institute for Animal Health), Naumburger Str. 96a, 07743 Jena, Germany
| | - Helmut Hotzel
- Institute of Bacterial Infections and Zoonoses, Friedrich-Loeffler-Institut (Federal Research Institute for Animal Health), Naumburger Str. 96a, 07743 Jena, Germany
| | - Peter Otto
- Institute of Bacterial Infections and Zoonoses, Friedrich-Loeffler-Institut (Federal Research Institute for Animal Health), Naumburger Str. 96a, 07743 Jena, Germany
| | - Kerstin Myrtennäs
- Department of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Umeå, Sweden
| | - Mats Forsman
- Department of CBRN Defence and Security, Swedish Defence Research Agency (FOI), Umeå, Sweden
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Hoang KV, Adcox HE, Fitch JR, Gordon DM, Curry HM, Schlesinger LS, White P, Gunn JS. AR-13, a Celecoxib Derivative, Directly Kills Francisella In Vitro and Aids Clearance and Mouse Survival In Vivo. Front Microbiol 2017; 8:1695. [PMID: 28955308 PMCID: PMC5600997 DOI: 10.3389/fmicb.2017.01695] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 08/23/2017] [Indexed: 12/15/2022] Open
Abstract
Francisella tularensis (F. tularensis) is the causative agent of tularemia and is classified as a Tier 1 select agent. No licensed vaccine is currently available in the United States and treatment of tularemia is confined to few antibiotics. In this study, we demonstrate that AR-13, a derivative of the cyclooxygenase-2 inhibitor celecoxib, exhibits direct in vitro bactericidal killing activity against Francisella including a type A strain of F. tularensis (SchuS4) and the live vaccine strain (LVS), as well as toward the intracellular proliferation of LVS in macrophages, without causing significant host cell toxicity. Identification of an AR-13-resistant isolate indicates that this compound has an intracellular target(s) and that efflux pumps can mediate AR-13 resistance. In the mouse model of tularemia, AR-13 treatment protected 50% of the mice from lethal LVS infection and prolonged survival time from a lethal dose of F. tularensis SchuS4. Combination of AR-13 with a sub-optimal dose of gentamicin protected 60% of F. tularensis SchuS4-infected mice from death. Taken together, these data support the translational potential of AR-13 as a lead compound for the further development of new anti-Francisella agents.
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Affiliation(s)
- Ky V Hoang
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, ColumbusOH, United States
| | - Haley E Adcox
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, ColumbusOH, United States
| | - James R Fitch
- The Institute for Genomic Medicine, Nationwide Children's Hospital, ColumbusOH, United States
| | - David M Gordon
- The Institute for Genomic Medicine, Nationwide Children's Hospital, ColumbusOH, United States
| | - Heather M Curry
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, ColumbusOH, United States
| | - Larry S Schlesinger
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, ColumbusOH, United States
| | - Peter White
- The Institute for Genomic Medicine, Nationwide Children's Hospital, ColumbusOH, United States.,Department of Pediatrics, The Ohio State University College of Medicine, ColumbusOH, United States
| | - John S Gunn
- Center for Microbial Interface Biology, Department of Microbial Infection and Immunity, The Ohio State University, ColumbusOH, United States
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14
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Benzoxazoles, Phthalazinones, and Arylurea-Based Compounds with IMP Dehydrogenase-Independent Antibacterial Activity against Francisella tularensis. Antimicrob Agents Chemother 2017; 61:AAC.00939-17. [PMID: 28739786 DOI: 10.1128/aac.00939-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 07/07/2017] [Indexed: 01/06/2023] Open
Abstract
Francisella tularensis is the causative agent of tularemia and a potential biowarfare agent. The virulence of F. tularensis is decreased by deletion of guaB, the gene encoding IMP dehydrogenase (IMPDH), suggesting that this enzyme is a target for antibacterial design. Here we report that F. tularensis growth is blocked by inhibitors of bacterial IMPDHs. Seventeen compounds from two different frameworks, designated the D and Q series, display antibacterial activities with MICs of <1 μM. These compounds are also active against intracellular infections. Surprisingly, antibacterial activity does not correlate with IMPDH inhibition. In addition, the presence of guanine does not affect the antibacterial activity of most compounds, nor does the deletion of guaB These observations suggest that antibacterial activity derives from inhibition of another target(s). Moreover, D compounds display antibacterial activity only against F. tularensis, suggesting the presence of a unique target or uptake mechanism. A ΔguaB mutant resistant to compound D73 contained a missense mutation (Gly45Cys) in nuoB, which encodes a subunit of bacterial complex I. Overexpression of the nuoB mutant conferred resistance to D73 in both wild-type and ΔguaB strains. This strain was not resistant to Q compounds, suggesting that a different off-target mechanism operates for these compounds. Several Q compounds are also effective against Mycobacterium tuberculosis, in which a second target has also been implicated, in addition to IMPDH. The fortuitous presence of multiple targets with overlapping structure-activity relationships presents an intriguing opportunity for the development of robust antibiotics that may avoid the emergence of resistance.
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15
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Sutera V, Hoarau G, Renesto P, Caspar Y, Maurin M. In vitro and in vivo evaluation of fluoroquinolone resistance associated with DNA gyrase mutations in Francisella tularensis, including in tularaemia patients with treatment failure. Int J Antimicrob Agents 2017; 50:377-383. [PMID: 28689870 DOI: 10.1016/j.ijantimicag.2017.03.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 03/20/2017] [Accepted: 03/22/2017] [Indexed: 01/23/2023]
Abstract
Fluoroquinolones (FQs) are highly effective for treating tularaemia, a zoonosis caused by Francisella tularensis, but failures and relapses remain common in patients with treatment delay or immunocompromised status. FQ-resistant strains of F. tularensis harboring mutations in the quinolone-resistance determining region (QRDR) of gyrA and gyrB, the genes encoding subunits A and B of DNA gyrase, have been selected in vitro. Such mutants have never been isolated from humans as this microorganism is difficult to culture. In this study, the presence of FQ-resistant mutants of F. tularensis was assessed in tularaemia patients using combined culture- and PCR-based approaches. We analyzed 42 F. tularensis strains and 82 tissue samples collected from 104 tularaemia cases, including 32 (30.7%) with FQ treatment failure or relapse. Forty F. tularensis strains and 55 clinical samples were obtained before any FQ treatment, while 2 strains and 15 tissue samples were collected after treatment. FQ resistance was evaluated by the minimum inhibitory concentration (MIC) for the bacterial strains, and by newly developed PCR-based methods targeting the gyrA and gyrB QRDRs for both the bacterial strains and the clinical samples. None of the F. tularensis strains displayed an increased MIC compared with FQ-susceptible controls. Neither gyrA nor gyrB QRDR mutation was found in bacterial strains and tissue samples tested, including those from patients with FQ treatment failure or relapse. Further phenotypic and genetic resistance traits should be explored to explain the poor clinical response to FQ treatment in such tularaemia patients.
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Affiliation(s)
- V Sutera
- Centre National de Référence des Francisella, Laboratoire de Bactériologie-Hygiène Hospitalière, Institut de Biologie et de Pathologie, Centre Hospitalier Universitaire Grenoble Alpes, CS 10217, 38043 Grenoble Cedex 9, France; Laboratoire Techniques de l'Ingénierie Médicale et de la Complexité-Informatique, Mathématiques et Applications (TIMC-IMAG), Université Grenoble Alpes, CS 10170, 38042 Grenoble cedex 9, France; Unité Mixte de Recherche 5525, Centre National de la Recherche Scientifique, 38042 Grenoble cedex 9, France
| | - G Hoarau
- Centre National de Référence des Francisella, Laboratoire de Bactériologie-Hygiène Hospitalière, Institut de Biologie et de Pathologie, Centre Hospitalier Universitaire Grenoble Alpes, CS 10217, 38043 Grenoble Cedex 9, France; Laboratoire Techniques de l'Ingénierie Médicale et de la Complexité-Informatique, Mathématiques et Applications (TIMC-IMAG), Université Grenoble Alpes, CS 10170, 38042 Grenoble cedex 9, France; Unité Mixte de Recherche 5525, Centre National de la Recherche Scientifique, 38042 Grenoble cedex 9, France
| | - P Renesto
- Laboratoire Techniques de l'Ingénierie Médicale et de la Complexité-Informatique, Mathématiques et Applications (TIMC-IMAG), Université Grenoble Alpes, CS 10170, 38042 Grenoble cedex 9, France; Unité Mixte de Recherche 5525, Centre National de la Recherche Scientifique, 38042 Grenoble cedex 9, France
| | - Y Caspar
- Centre National de Référence des Francisella, Laboratoire de Bactériologie-Hygiène Hospitalière, Institut de Biologie et de Pathologie, Centre Hospitalier Universitaire Grenoble Alpes, CS 10217, 38043 Grenoble Cedex 9, France; Laboratoire Techniques de l'Ingénierie Médicale et de la Complexité-Informatique, Mathématiques et Applications (TIMC-IMAG), Université Grenoble Alpes, CS 10170, 38042 Grenoble cedex 9, France; Unité Mixte de Recherche 5525, Centre National de la Recherche Scientifique, 38042 Grenoble cedex 9, France
| | - M Maurin
- Centre National de Référence des Francisella, Laboratoire de Bactériologie-Hygiène Hospitalière, Institut de Biologie et de Pathologie, Centre Hospitalier Universitaire Grenoble Alpes, CS 10217, 38043 Grenoble Cedex 9, France; Laboratoire Techniques de l'Ingénierie Médicale et de la Complexité-Informatique, Mathématiques et Applications (TIMC-IMAG), Université Grenoble Alpes, CS 10170, 38042 Grenoble cedex 9, France; Unité Mixte de Recherche 5525, Centre National de la Recherche Scientifique, 38042 Grenoble cedex 9, France.
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16
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Wekselman I, Zimmerman E, Davidovich C, Belousoff M, Matzov D, Krupkin M, Rozenberg H, Bashan A, Friedlander G, Kjeldgaard J, Ingmer H, Lindahl L, Zengel JM, Yonath A. The Ribosomal Protein uL22 Modulates the Shape of the Protein Exit Tunnel. Structure 2017; 25:1233-1241.e3. [PMID: 28689968 DOI: 10.1016/j.str.2017.06.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 05/08/2017] [Accepted: 06/02/2017] [Indexed: 10/19/2022]
Abstract
Erythromycin is a clinically useful antibiotic that binds to an rRNA pocket in the ribosomal exit tunnel. Commonly, resistance to erythromycin is acquired by alterations of rRNA nucleotides that interact with the drug. Mutations in the β hairpin of ribosomal protein uL22, which is rather distal to the erythromycin binding site, also generate resistance to the antibiotic. We have determined the crystal structure of the large ribosomal subunit from Deinococcus radiodurans with a three amino acid insertion within the β hairpin of uL22 that renders resistance to erythromycin. The structure reveals a shift of the β hairpin of the mutated uL22 toward the interior of the exit tunnel, triggering a cascade of structural alterations of rRNA nucleotides that propagate to the erythromycin binding pocket. Our findings support recent studies showing that the interactions between uL22 and specific sequences within nascent chains trigger conformational rearrangements in the exit tunnel.
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Affiliation(s)
- Itai Wekselman
- Department of Structural Biology, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Ella Zimmerman
- Department of Structural Biology, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Chen Davidovich
- Department of Structural Biology, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Matthew Belousoff
- Department of Structural Biology, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Donna Matzov
- Department of Structural Biology, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Miri Krupkin
- Department of Structural Biology, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Haim Rozenberg
- Department of Structural Biology, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Anat Bashan
- Department of Structural Biology, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Gilgi Friedlander
- The Ilana and Pascal Mantoux Institute for Bioinformatics, The Nancy and Stephen Grand Israel National Center for Personalized Medicine, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Jette Kjeldgaard
- Department of Veterinary Disease Biology, University of Copenhagen, 1870 Frederiksbergc, Denmark
| | - Hanne Ingmer
- Department of Veterinary Disease Biology, University of Copenhagen, 1870 Frederiksbergc, Denmark
| | - Lasse Lindahl
- Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
| | - Janice M Zengel
- Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
| | - Ada Yonath
- Department of Structural Biology, The Weizmann Institute of Science, Rehovot 7610001, Israel.
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17
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A spontaneous mutation in kdsD, a biosynthesis gene for 3 Deoxy-D-manno-Octulosonic Acid, occurred in a ciprofloxacin resistant strain of Francisella tularensis and caused a high level of attenuation in murine models of tularemia. PLoS One 2017; 12:e0174106. [PMID: 28328947 PMCID: PMC5362203 DOI: 10.1371/journal.pone.0174106] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 03/03/2017] [Indexed: 12/26/2022] Open
Abstract
Francisella tularensis, a gram-negative facultative intracellular bacterial pathogen, is the causative agent of tularemia and able to infect many mammalian species, including humans. Because of its ability to cause a lethal infection, low infectious dose, and aerosolizable nature, F. tularensis subspecies tularensis is considered a potential biowarfare agent. Due to its in vitro efficacy, ciprofloxacin is one of the antibiotics recommended for post-exposure prophylaxis of tularemia. In order to identify therapeutics that will be efficacious against infections caused by drug resistant select-agents and to better understand the threat, we sought to characterize an existing ciprofloxacin resistant (CipR) mutant in the Schu S4 strain of F. tularensis by determining its phenotypic characteristics and sequencing the chromosome to identify additional genetic alterations that may have occurred during the selection process. In addition to the previously described genetic alterations, the sequence of the CipR mutant strain revealed several additional mutations. Of particular interest was a frameshift mutation within kdsD which encodes for an enzyme necessary for the production of 3-Deoxy-D-manno-Octulosonic Acid (KDO), an integral component of the lipopolysaccharide (LPS). A kdsD mutant was constructed in the Schu S4 strain. Although it was not resistant to ciprofloxacin, the kdsD mutant shared many phenotypic characteristics with the CipR mutant, including growth defects under different conditions, sensitivity to hydrophobic agents, altered LPS profiles, and attenuation in multiple models of murine tularemia. This study demonstrates that the KdsD enzyme is essential for Francisella virulence and may be an attractive therapeutic target for developing novel medical countermeasures.
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18
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Ribosomal Mutations Conferring Macrolide Resistance in Legionella pneumophila. Antimicrob Agents Chemother 2017; 61:AAC.02188-16. [PMID: 28069647 DOI: 10.1128/aac.02188-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 01/04/2017] [Indexed: 01/15/2023] Open
Abstract
Monitoring the emergence of antibiotic resistance is a recent issue in the treatment of Legionnaires' disease. Macrolides are recommended as first-line therapy, but resistance mechanisms have not been studied in Legionella species. Our aim was to determine the molecular basis of macrolide resistance in L. pneumophila Twelve independent lineages from a common susceptible L. pneumophila ancestral strain were propagated under conditions of erythromycin or azithromycin pressure to produce high-level macrolide resistance. Whole-genome sequencing was performed on 12 selected clones, and we investigated mutations common to all lineages. We reconstructed the dynamics of mutation for each lineage and demonstrated their involvement in decreased susceptibility to macrolides. The resistant mutants were produced in a limited number of passages to obtain a 4,096-fold increase in erythromycin MICs. Mutations affected highly conserved 5-amino-acid regions of L4 and L22 ribosomal proteins and of domain V of 23S rRNA (G2057, A2058, A2059, and C2611 nucleotides). The early mechanisms mainly affected L4 and L22 proteins and induced a 32-fold increase in the MICs of the selector drug. Additional mutations related to 23S rRNA mostly occurred later and were responsible for a major increase of macrolide MICs, depending on the mutated nucleotide, the substitution, and the number of mutated genes among the three rrl copies. The major mechanisms of the decreased susceptibility to macrolides in L. pneumophila and their dynamics were determined. The results showed that macrolide resistance could be easily selected in L. pneumophila and warrant further investigations in both clinical and environmental settings.
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19
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Karlsson E, Golovliov I, Lärkeryd A, Granberg M, Larsson E, Öhrman C, Niemcewicz M, Birdsell D, Wagner DM, Forsman M, Johansson A. Clonality of erythromycin resistance in Francisella tularensis. J Antimicrob Chemother 2016; 71:2815-23. [PMID: 27334667 DOI: 10.1093/jac/dkw235] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Accepted: 05/17/2016] [Indexed: 01/20/2023] Open
Abstract
OBJECTIVES We analysed diverse strains of Francisella tularensis subsp. holarctica to assess if its division into biovars I and II is associated with specific mutations previously linked to erythromycin resistance and to determine the distribution of this resistance trait across this subspecies. METHODS Three-hundred and fourteen F. tularensis subsp. holarctica strains were tested for erythromycin susceptibility and whole-genome sequences for these strains were examined for SNPs in genes previously associated with erythromycin resistance. Each strain was assigned to a global phylogenetic framework using genome-wide canonical SNPs. The contribution of a specific SNP to erythromycin resistance was examined using allelic exchange. The geographical distribution of erythromycin-resistant F. tularensis strains was further investigated by literature search. RESULTS There was a perfect correlation between biovar II strains (erythromycin resistance) and the phylogenetic group B.12. Only B.12 strains had an A → C SNP at position 2059 in the three copies of the rrl gene. Introducing 2059C into an rrl gene of an erythromycin-susceptible F. tularensis strain resulted in resistance. An additional 1144 erythromycin-resistant strains were identified from the scientific literature, all of them from Eurasia. CONCLUSIONS Erythromycin resistance in F. tularensis is caused by an A2059C rrl gene mutation, which exhibits a strictly clonal inheritance pattern found only in phylogenetic group B.12. This group is an extremely successful clone, representing the most common type of F. tularensis throughout Eurasia.
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Affiliation(s)
- Edvin Karlsson
- CBRN Defence and Security, Swedish Defence Research Agency, Umeå, Sweden
| | - Igor Golovliov
- Department of Clinical Microbiology, Clinical Bacteriology, and Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden
| | - Adrian Lärkeryd
- CBRN Defence and Security, Swedish Defence Research Agency, Umeå, Sweden
| | - Malin Granberg
- CBRN Defence and Security, Swedish Defence Research Agency, Umeå, Sweden
| | - Eva Larsson
- CBRN Defence and Security, Swedish Defence Research Agency, Umeå, Sweden
| | - Caroline Öhrman
- CBRN Defence and Security, Swedish Defence Research Agency, Umeå, Sweden
| | - Marcin Niemcewicz
- Wojskowy Instytut Higieny i Epidemioligii, Biological Threat Identification and Countermeasure Center, Warsaw, Poland
| | - Dawn Birdsell
- Department of Biological Sciences and Center for Microbial Genetics and Genomics, Northern Arizona University, Flagstaff, AZ, USA
| | - David M Wagner
- Department of Biological Sciences and Center for Microbial Genetics and Genomics, Northern Arizona University, Flagstaff, AZ, USA
| | - Mats Forsman
- CBRN Defence and Security, Swedish Defence Research Agency, Umeå, Sweden
| | - Anders Johansson
- Department of Clinical Microbiology, Clinical Bacteriology, and Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden
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20
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Maurin M, Gyuranecz M. Tularaemia: clinical aspects in Europe. THE LANCET. INFECTIOUS DISEASES 2016; 16:113-124. [PMID: 26738841 DOI: 10.1016/s1473-3099(15)00355-2] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Revised: 09/17/2015] [Accepted: 09/21/2015] [Indexed: 10/22/2022]
Abstract
Tularaemia is a zoonotic disease caused by Francisella tularensis, a Gram-negative, facultative intracellular bacterium. Typically, human and animal infections are caused by F tularensis subspecies tularensis (type A) strains mainly in Canada and USA, and F tularensis subspecies holarctica (type B) strains throughout the northern hemisphere, including Europe. In the past, the epidemiological, clinical, therapeutic, and prognostic aspects of tularaemia reported in the English medical literature were mainly those that had been reported in the USA, where the disease was first described. Tularaemia has markedly changed in the past decade, and a large number of studies have provided novel data for the disease characteristics in Europe. In this Review we aim to emphasise the specific and variable aspects of tularaemia in different European countries. In particular, two natural lifecycles of F tularensis have been described in this continent, although not fully characterised, which are associated with different modes of transmission, clinical features, and public health burdens of tularaemia.
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Affiliation(s)
- Max Maurin
- Centre National de Référence des Francisella, Département des Agents Infectieux, Institut de Biologie et Pathologie, CHU de Grenoble, Grenoble, cedex 9, France; Université Grenoble Alpes and Centre National de la Recherche Scientifique, Laboratoire Adaptation et Pathogénie des Microorganismes, IMR 5163, Grenoble, France.
| | - Miklós Gyuranecz
- Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary; OIE Reference Laboratory for Tularemia, Budapest, Country
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21
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Gunnell MK, Robison RA, Adams BJ. Natural Selection in Virulence Genes of Francisella tularensis. J Mol Evol 2016; 82:264-78. [PMID: 27177502 DOI: 10.1007/s00239-016-9743-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 04/29/2016] [Indexed: 02/06/2023]
Abstract
A fundamental tenet of evolution is that alleles that are under negative selection are often deleterious and confer no evolutionary advantage. Negatively selected alleles are removed from the gene pool and are eventually extinguished from the population. Conversely, alleles under positive selection do confer an evolutionary advantage and lead to an increase in the overall fitness of the organism. These alleles increase in frequency until they eventually become fixed in the population. Francisella tularensis is a zoonotic pathogen and a potential biothreat agent. The most virulent type of F. tularensis, Type A, is distributed across North America with Type A.I occurring mainly in the east and Type A.II appearing mainly in the west. F. tularensis is thought to be a genome in decay (losing genes) because of the relatively large number of pseudogenes present in its genome. We hypothesized that the observed frequency of gene loss/pseudogenes may be an artifact of evolution in response to a changing environment, and that genes involved in virulence should be under strong positive selection. To test this hypothesis, we sequenced and compared whole genomes of Type A.I and A.II isolates. We analyzed a subset of virulence and housekeeping genes from several F. tularensis subspecies genomes to ascertain the presence and extent of positive selection. Eleven previously identified virulence genes were screened for positive selection along with 10 housekeeping genes. Analyses of selection yielded one housekeeping gene and 7 virulence genes which showed significant evidence of positive selection at loci implicated in cell surface structures and membrane proteins, metabolism and biosynthesis, transcription, translation and cell separation, and substrate binding and transport. Our results suggest that while the loss of functional genes through disuse could be accelerated by negative selection, the genome decay in Francisella could also be the byproduct of adaptive evolution driven by complex interactions between host, pathogen, and thier environment, as evidenced by several of its virulence genes which are undergoing strong, positive selection.
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Affiliation(s)
- Mark K Gunnell
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, 84602, USA. .,Microbiology Branch, Life Sciences Division, Dugway Proving Ground, Dugway, UT, 84022, USA.
| | - Richard A Robison
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, 84602, USA
| | - Byron J Adams
- Department of Biology, Brigham Young University, Provo, UT, 84602, USA
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22
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Dean SN, van Hoek ML. Screen of FDA-approved drug library identifies maprotiline, an antibiofilm and antivirulence compound with QseC sensor-kinase dependent activity in Francisella novicida. Virulence 2016; 6:487-503. [PMID: 26155740 DOI: 10.1080/21505594.2015.1046029] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Development of new therapeutics against Select Agents such as Francisella is critical preparation in the event of bioterrorism. Testing FDA-approved drugs for this purpose may yield new activities unrelated to their intended purpose and may hasten the discovery of new therapeutics. A library of 420 FDA-approved drugs was screened for antibiofilm activity against a model organism for human tularemia, Francisella (F.) novicida, excluding drugs that significantly inhibited growth. The initial screen was based on the 2-component system (TCS) dependent biofilm effect, thus, the QseC dependence of maprotiline anti-biofilm action was demonstrated. By comparing their FDA-approved uses, chemical structures, and other properties of active drugs, toremifene and polycyclic antidepressants maprotiline and chlorpromazine were identified as being highly active against F. novicida biofilm formation. Further down-selection excluded toremifene for its membrane active activity and chlorpromazine for its high antimicrobial activity. The mode of action of maprotiline against F. novicida was sought. It was demonstrated that maprotiline was able to significantly down-regulate the expression of the virulence factor IglC, encoded on the Francisella Pathogenicity Island (FPI), suggesting that maprotiline is exerting an effect on bacterial virulence. Further studies showed that maprotiline significantly rescued F. novicida infected wax worm larvae. In vivo studies demonstrated that maprotiline treatment could prolong time to disease onset and survival in F. novicida infected mice. These results suggest that an FDA-approved drug such as maprotiline has the potential to combat Francisella infection as an antivirulence agent, and may have utility in combination with antibiotics.
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Affiliation(s)
- Scott N Dean
- a National Center for Biodefense and Infectious Diseases ; Manassas , VA , USA
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Aloni-Grinstein R, Shifman O, Lazar S, Steinberger-Levy I, Maoz S, Ber R. A rapid real-time quantitative PCR assay to determine the minimal inhibitory extracellular concentration of antibiotics against an intracellular Francisella tularensis Live Vaccine Strain. Front Microbiol 2015; 6:1213. [PMID: 26579112 PMCID: PMC4630301 DOI: 10.3389/fmicb.2015.01213] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 10/19/2015] [Indexed: 12/17/2022] Open
Abstract
Francisella tularensis is a highly virulent facultative intracellular bacterium. The lack of a safe and efficient vaccine makes antibiotics the preferred treatment. F. tularensis antibiotic susceptibility tests are based on the in vitro standard CLSI-approved microdilution method for determining the MIC. However, limited data are available regarding the minimal inhibitory extracellular concentration (MIEC) needed to eradicate intracellular bacteria. Here, we evaluated the MIEC values of various WHO-recommended antibiotics and compared the MIEC values to the established MICs. We describe a rapid 3-h quantitative PCR (qPCR) intracellular antibiogram assay, which yields comparable MIEC values to those obtained by the classical 72-h cfu assay. This rapid qPCR assay is highly advantageous in light of the slow growth rates of F. tularensis. Our results showed that the MIECs obtained for doxycycline, chloramphenicol and ciprofloxacin were indicative of intracellular activity. Gentamicin was not effective against intracellular bacteria for at least 32 h post treatment, raising the question of whether slow-penetrating gentamicin should be used for certain stages of the disease. We suggest that the qPCR intracellular antibiogram assay may be used to screen for potentially active antibiotics against intracellular F. tularensis as well as to detect strains with acquired resistance to recommended antibiotics.
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Affiliation(s)
- Ronit Aloni-Grinstein
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness Ziona, Israel
| | - Ohad Shifman
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness Ziona, Israel
| | - Shlomi Lazar
- Department of Pharmacology, Israel Institute for Biological Research Ness Ziona, Israel
| | - Ida Steinberger-Levy
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness Ziona, Israel
| | - Sharon Maoz
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness Ziona, Israel
| | - Raphael Ber
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness Ziona, Israel
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Abstract
Francisella tularensis is a category A bioterrorism agent. It is the etiological agent of tularemia, a zoonotic disease found throughout the northern hemisphere. The intentional spread of F. tularensis aerosols would probably lead to severe and often fatal pneumonia cases, but also secondary cases from contaminated animals and environments. We are not ready to face such a situation. No vaccine is currently available. A few antibiotics are active against F. tularensis, but strains resistant to these antibiotics could be used in the context of bioterrorism. We need new therapeutic strategies to fight against category A bioterrorism agents, including development of new drugs inhibiting F. tularensis growth and/or virulence, or enhancing the host response to infection by this pathogen.
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Affiliation(s)
- Max Maurin
- Centre National de Référence des Francisella, Département des Agents Infectieux, Institut de Biologie et de Pathologie, CHU de Grenoble, F-38043, Grenoble, France
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Origgi FC, Frey J, Pilo P. Characterisation of a new group of Francisella tularensis subsp. holarctica in Switzerland with altered antimicrobial susceptibilities, 1996 to 2013. ACTA ACUST UNITED AC 2014; 19. [PMID: 25080140 DOI: 10.2807/1560-7917.es2014.19.29.20858] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Molecular analysis of Francisella tularensis subsp. holarctica isolates from humans and animals revealed the presence of two subgroups belonging to the phylogenetic groups B.FTNF002-00 and B.13 in Switzerland. This finding suggests a broader spread of this group in Europe than previously reported. Until recently, only strains belonging to the Western European cluster (group B.FTNF002-00) had been isolated from tularaemia cases in Switzerland. The endemic strains belonging to group B.FTNF002-00 are sensitive to erythromycin, in contrast to the strains of the newly detected group B.13 that are resistant to this antibiotic. All the strains tested were susceptible to ciprofloxacin, streptomycin, gentamicin, nalidixic acid and chloramphenicol but showed reduced susceptibility to tetracycline when tested in a growth medium supplemented with divalent cations. The data show a previously undetected spread of group B.13 westwards in Europe, associated with changes in the antibiotic resistance profile relevant to treatment of tularaemia.
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Affiliation(s)
- F C Origgi
- Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
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Boisset S, Caspar Y, Sutera V, Maurin M. New therapeutic approaches for treatment of tularaemia: a review. Front Cell Infect Microbiol 2014; 4:40. [PMID: 24734221 PMCID: PMC3975101 DOI: 10.3389/fcimb.2014.00040] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Accepted: 03/13/2014] [Indexed: 12/23/2022] Open
Abstract
Antibiotic treatment of tularaemia is based on a few drugs, including the fluoroquinolones (e.g., ciprofloxacin), the tetracyclines (e.g., doxycycline), and the aminoglycosides (streptomycin and gentamicin). Because no effective and safe vaccine is currently available, tularaemia prophylaxis following proven exposure to F. tularensis also relies on administration of antibiotics. A number of reasons make it necessary to search for new therapeutic alternatives: the potential toxicity of first-line drugs, especially in children and pregnant women; a high rate of treatment relapses and failures, especially for severe and/or suppurated forms of the disease; and the possible use of antibiotic-resistant strains in the context of a biological threat. This review presents novel therapeutic approaches that have been explored in recent years to improve tularaemia patients' management and prognosis. These new strategies have been evaluated in vitro, in axenic media and cell culture systems and/or in animal models. First, the activities of newly available antibiotic compounds were evaluated against F. tularensis, including tigecycline (a glycylcycline), ketolides (telithromycin and cethromycin), and fluoroquinolones (moxifloxacin, gatifloxacin, trovafloxacin and grepafloxacin). The liposome delivery of some antibiotics was evaluated. The effect of antimicrobial peptides against F. tularensis was also considered. Other drugs were evaluated for their ability to suppress the intracellular multiplication of F. tularensis. The effects of the modulation of the innate immune response (especially via TLR receptors) on the course of F. tularensis infection was characterized. Another approach was the administration of specific antibodies to induce passive resistance to F. tularensis infection. All of these studies highlight the need to develop new therapeutic strategies to improve the management of patients with tularaemia. Many possibilities exist, some unexplored. Moreover, it is likely that new therapeutic alternatives that are effective against this intracellular pathogen could be, at least partially, extrapolated to other human pathogens.
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Affiliation(s)
- Sandrine Boisset
- Laboratoire de Bactériologie, Institut de Biologie et de Pathologie, CHU de Grenoble Grenoble, France ; Université Joseph Fourier-Grenoble 1 Grenoble, France ; Laboratoire Adaptation et Pathogénie des Micro-Organismes, CNRS/UJF, UMR 5163 Grenoble, France
| | - Yvan Caspar
- Laboratoire de Bactériologie, Institut de Biologie et de Pathologie, CHU de Grenoble Grenoble, France ; Université Joseph Fourier-Grenoble 1 Grenoble, France ; Laboratoire Adaptation et Pathogénie des Micro-Organismes, CNRS/UJF, UMR 5163 Grenoble, France
| | - Vivien Sutera
- Laboratoire de Bactériologie, Institut de Biologie et de Pathologie, CHU de Grenoble Grenoble, France ; Université Joseph Fourier-Grenoble 1 Grenoble, France ; Laboratoire Adaptation et Pathogénie des Micro-Organismes, CNRS/UJF, UMR 5163 Grenoble, France
| | - Max Maurin
- Laboratoire de Bactériologie, Institut de Biologie et de Pathologie, CHU de Grenoble Grenoble, France ; Université Joseph Fourier-Grenoble 1 Grenoble, France ; Laboratoire Adaptation et Pathogénie des Micro-Organismes, CNRS/UJF, UMR 5163 Grenoble, France
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27
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Celik T, Kosker M, Kirboga K. An atypical case of tularemia presented with pseudoptosis. Infection 2014; 42:785-8. [PMID: 24659144 DOI: 10.1007/s15010-014-0613-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 03/05/2014] [Indexed: 11/26/2022]
Abstract
We report an unusual case of tularemia involving pseudoptosis associated with deterioration of the lymphatic drainage system extending from the upper eyelid to the preauricular lymph nodes. A 16-week pregnant patient was admitted with an absess on the neck, preauricular lymphadenopathy, and pseudoptosis on the left side. The micro-agglutination test was positive for Francisella tularensis antibody at a titer of 1/200. The absess was surgically drained and oral cefuroxime was given for 6 weeks. Two weeks after drainage, the pseudoptosis improved due to the recovery of lymphatic drainage system of the eyelid and remission of the absess on the neck. Our case report contributes to the medical literature on tularemia during pregnancy and informs healthcare professionals on the management of the infection in such cases.
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Affiliation(s)
- T Celik
- Department of Ophthalmology, Bolu Gerede State Hospital, Seviller St., Gerede-Bolu, 14900, Turkey,
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Sutera V, Caspar Y, Boisset S, Maurin M. A new dye uptake assay to test the activity of antibiotics against intracellular Francisella tularensis. Front Cell Infect Microbiol 2014; 4:36. [PMID: 24672776 PMCID: PMC3957058 DOI: 10.3389/fcimb.2014.00036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 02/24/2014] [Indexed: 11/13/2022] Open
Abstract
Francisella tularensis, a facultative intracellular bacterium, is the aetiological agent of tularaemia. Antibiotic treatment of this zoonosis is based on the administration of a fluoroquinolone or a tetracycline for cases with mild to moderate severity, whereas an aminoglycoside (streptomycin or gentamicin) is advocated for severe cases. However, treatment failures and relapses remain frequent, especially in patients suffering from chronic lymph node suppuration. Therefore, new treatment alternatives are needed. We have developed a dye uptake assay for determination of minimal inhibitory extracellular concentrations (MIECs) of antibiotics against intracellular F. tularensis, and validated the method by comparing the results obtained using a CFU-enumerating method. We also compared MIECs with MICs of the same compounds determined using a CLSI broth microdilution method. We tested the activity of 11 antibiotics against two clinical strains of F. tularensis subsp. holarctica isolated in France. Both strains displayed low MICs (≤1 μg/mL) to fluoroquinolones (ciprofloxacin, levofloxacin and moxifloxacin), gentamicin, doxycycline and rifampicin. Higher MICs (≥8 μg/mL) were found for carbapenems (imipenem and meropenem), daptomycin and linezolid. Erythromycin MICs were 4.0 and 16.0 μg/mL, respectively, for the two clinical strains. MIECs were almost the same with the two methods used. They were concordant with MICs, except for erythromycin and linezolid (respectively, four and eight times more active against intracellular F. tularensis) and gentamicin (four to eight times less active against intracellular F. tularensis). This study validated the dye uptake assay as a new tool for determination of the activity of a large panel of antibiotics against intracellular F. tularensis. This test confirmed the intracellular activity of first-line antibiotics used for tularaemia treatment, but also revealed significant activity of linezolid against intracellular F. tularensis.
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Affiliation(s)
- Vivien Sutera
- Laboratoire de Bactériologie, Département des Agents Infectieux, Institut de Biologie et de Pathologie, Centre Hospitalier Universitaire Grenoble Grenoble, France ; Laboratoire Adaptation et Pathogénie des Micro-Organismes, Université Joseph Fourier-Grenoble 1 Grenoble Cedex 9, France ; CNRS, UMR 5163 Grenoble, France
| | - Yvan Caspar
- Laboratoire de Bactériologie, Département des Agents Infectieux, Institut de Biologie et de Pathologie, Centre Hospitalier Universitaire Grenoble Grenoble, France ; Laboratoire Adaptation et Pathogénie des Micro-Organismes, Université Joseph Fourier-Grenoble 1 Grenoble Cedex 9, France ; CNRS, UMR 5163 Grenoble, France
| | - Sandrine Boisset
- Laboratoire de Bactériologie, Département des Agents Infectieux, Institut de Biologie et de Pathologie, Centre Hospitalier Universitaire Grenoble Grenoble, France ; Laboratoire Adaptation et Pathogénie des Micro-Organismes, Université Joseph Fourier-Grenoble 1 Grenoble Cedex 9, France ; CNRS, UMR 5163 Grenoble, France
| | - Max Maurin
- Laboratoire de Bactériologie, Département des Agents Infectieux, Institut de Biologie et de Pathologie, Centre Hospitalier Universitaire Grenoble Grenoble, France ; Laboratoire Adaptation et Pathogénie des Micro-Organismes, Université Joseph Fourier-Grenoble 1 Grenoble Cedex 9, France ; CNRS, UMR 5163 Grenoble, France
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29
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Sutera V, Levert M, Burmeister WP, Schneider D, Maurin M. Evolution toward high-level fluoroquinolone resistance in Francisella species. J Antimicrob Chemother 2013; 69:101-10. [PMID: 23963236 DOI: 10.1093/jac/dkt321] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES Francisella tularensis, a CDC class A potential bioterrorism agent, is a Gram-negative bacterium responsible for tularaemia. Understanding the mechanisms of resistance to antibiotics used as first-line treatment is of major security relevance. METHODS We propagated the three parental reference strains Francisella tularensis subsp. holarctica live vaccine strain, Francisella novicida and Francisella philomiragia with increasing concentrations of ciprofloxacin, a fluoroquinolone used as curative and prophylactic treatment for tularaemia. This evolution procedure provided us with high-level ciprofloxacin-resistant mutants and all evolutionary intermediates towards high-level resistance. We determined the resistance levels to other fluoroquinolones (levofloxacin and moxifloxacin) and other antibiotic families (aminoglycosides, tetracyclines and macrolides) and characterized the genetic changes in the fluoroquinolone target genes encoding DNA gyrase and topoisomerase IV. RESULTS All high-level resistant mutants shared cross-resistance to the tested fluoroquinolones, while some also revealed striking levels of cross-resistance to other clinically relevant antibiotic classes. High-level resistant mutants carried one to three mutations, including some not previously reported. We mapped all mutations onto known topoisomerase three-dimensional structures. Along the pathways towards high-level resistance, we identified complex evolutionary trajectories including polymorphic states and additional resistance mechanisms likely to be associated with efflux processes. CONCLUSIONS Our data demonstrated the efficiency and speed of in vitro production of mutants highly resistant to fluoroquinolones in Francisella species. They emphasize the urgent need to identify all antibiotic resistance mechanisms in these species, develop molecular tools for their detection and design new therapeutic alternatives for tularaemia.
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Affiliation(s)
- Vivien Sutera
- Centre Hospitalier Universitaire Grenoble, CS10217, 38043 Grenoble cedex 9, France
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Dentan C, Pavese P, Pelloux I, Boisset S, Brion JP, Stahl JP, Maurin M. Treatment of tularemia in pregnant woman, France. Emerg Infect Dis 2013; 19:996-8. [PMID: 23735285 PMCID: PMC3713841 DOI: 10.3201/eid1906.130138] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
A pregnant woman who had oropharyngeal tularemia underwent treatment with azithromycin and lymph node resection and recovered without obstetrical complication or infection in the child. Azithromycin represents a first-line treatment option for tularemia during pregnancy in regions where the infecting strains of Francisella tularensis have no natural resistance to macrolides.
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Mackie RS, McKenney ES, van Hoek ML. Resistance of Francisella novicida to fosmidomycin associated with mutations in the glycerol-3-phosphate transporter. Front Microbiol 2012; 3:226. [PMID: 22905031 PMCID: PMC3417576 DOI: 10.3389/fmicb.2012.00226] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 06/01/2012] [Indexed: 01/23/2023] Open
Abstract
The methylerythritol phosphate (MEP) pathway is essential in most prokaryotes and some lower eukaryotes but absent from human cells, and is a validated target for antimicrobial drug development. The formation of MEP is catalyzed by 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR). MEP pathway genes have been identified in many category A and B biothreat agents, including Francisella tularensis, which causes the zoonosis tularemia. Fosmidomycin (Fos) inhibits purified Francisella DXR. This compound also inhibits the growth of F. tularensis NIH B38, F. novicida and F. tularensis subsp. holarctica LVS bacteria. Related compounds such as FR900098 and the lipophilic prodrug of FR900098 (compound 1) have been developed to improve the bioavailability of these DXR inhibitors. In performing disk-inhibition assays with these compounds, we observed breakthrough colonies of F. novicida in the presence of Fos, suggesting spontaneous development of Fos resistance (Fos(R)). Fos(R) bacteria had decreased sensitivity to both Fos and FR900098. The two most likely targets for the development of mutants would be the DXR enzyme itself or the glycerol-3-phosphate transporter (GlpT) that allows entry of Fos into the bacteria. Sensitivity of Fos(R)F. novicida bacteria to compound 1 was not abated suggesting that spontaneous resistance is not due to mutation of DXR. We thus predicted that the glpT transporter may be mutated leading to this resistant phenotype. Supporting this, transposon insertion mutants at the glpT locus were also found to be resistant to Fos. DNA sequencing of four different spontaneous Fos(R) colonies demonstrated a variety of deletions in the glpT coding region. The overall frequency of Fos(R) mutations in F. novicida was determined to be 6.3 × 10(-8). Thus we conclude that one mechanism of resistance of F. novicida to Fos is caused by mutations in GlpT. This is the first description of spontaneous mutations in Francisella leading to Fos(R).
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Affiliation(s)
- Ryan S Mackie
- School of Systems Biology, George Mason University Manassas, VA, USA
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32
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Georgi E, Schacht E, Scholz HC, Splettstoesser WD. Standardized broth microdilution antimicrobial susceptibility testing of Francisella tularensis subsp. holarctica strains from Europe and rare Francisella species. J Antimicrob Chemother 2012; 67:2429-33. [PMID: 22763567 DOI: 10.1093/jac/dks238] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES Tularaemia is a widespread zoonosis in Europe caused by Francisella tularensis subsp. holarctica. Because of a lack of standardized CLSI-approved antibiotic susceptibility data from European Francisella strains, the antibiotic susceptibilities of a selection of F. tularensis subsp. holarctica isolates originating from Germany, Austria, France, Spain and other European countries were determined. Rarely isolated species and subspecies of Francisella such as Francisella philomiragia, F. tularensis subsp. novicida and F. tularensis subsp. mediasiatica as well as the type strain of Francisella hispaniensis were included in this study. METHODS MIC data were obtained using cation-adjusted Mueller-Hinton broth with a 2% growth supplement. The broth microdilution testing system comprised 14 antibiotics, including gentamicin, streptomycin, ciprofloxacin and tetracycline. RESULTS All of the 91 strains tested were susceptible to aminoglycosides, quinolones, tetracycline and chloramphenicol. The antimicrobial susceptibility of rare Francisellae was similar to the antibiotic profile of F. tularensis subsp. holarctica strains. For erythromycin, we detected two geographically distinct groups of F. tularensis subsp. holarctica isolates in western Europe. One group was resistant and the other one was susceptible. Both groups overlapped in a small region in Germany. CONCLUSIONS Being performed in accordance with CLSI criteria, this study provides reliable data on antibiotic susceptibility patterns of European Francisella isolates. The standardized methodology of this study can be used for testing of suspicious colonies from clinical specimens for therapeutic guidance. Based on the results, aminoglycosides or quinolones are recommended as first-choice antibiotics for the therapy of F. hispaniensis, F. philomiragia or F. tularensis subsp. novicida infections in immunocompromised patients.
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Affiliation(s)
- Enrico Georgi
- Bundeswehr Institute of Microbiology, Neuherbergstrasse 11, D-80937 Munich, Germany.
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Maurin M, Pelloux I, Brion JP, Del Bano JN, Picard A. Human Tularemia in France, 2006-2010. Clin Infect Dis 2011; 53:e133-41. [DOI: 10.1093/cid/cir612] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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