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Mokoala KMG, Ndlovu H, Lawal I, Sathekge MM. PET/CT and SPECT/CT for Infection in Joints and Bones: An Overview and Future Directions. Semin Nucl Med 2024; 54:394-408. [PMID: 38016897 DOI: 10.1053/j.semnuclmed.2023.10.007] [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: 10/27/2023] [Accepted: 10/30/2023] [Indexed: 11/30/2023]
Abstract
Infections of the bones and joints, if misdiagnosed, may result in serious morbidity and even mortality. A prompt diagnosis followed by appropriate management may reduce the socioeconomic impact of bone and joint infections. Morphologic imaging such as ultrasound and plain radiographs form the first line investigations, however, in early infections findings may be negative or nonspecific. Nuclear medicine imaging techniques play a complementary role to morphologic imaging in the diagnosis of bone and joint infections. The availability of hybrid systems (SPECT/CT, SPECT/MRI, PET/CT or PET/MRI) offers improved specificity with ability to assess the extent of infection. Bone scans are useful as a gatekeeper wherein negative scans rule out sepsis with a good accuracy, however positive scans are nondiagnostic and more specific tracers should be considered. These include the use of labeled white blood cells and antigranulocyte antibodies. Various qualitative and quantitative interpretation criteria have been suggested to improve the specificity of the scans. PET has better image resolution and 18F-FDG is the major tracer for PET imaging with applications in oncology and inflammatory/infective disorders. It has demonstrated improved sensitivity over the SPECT based tracers, however, still suffers from lack of specificity. 18F-FDG PET has been used to monitor therapy in bone and joint infections. Other less studied, noncommercialized SPECT and PET tracers such as 111In-Biotin, 99mTc-Ubiquicidin, 18F-Na-Fluoride, 18F-labeled white blood cells and 124I-Fialuridine to name a few have shown great promise, however, their role in various bone and joint infections has not been established. Hybrid imaging with PET or PET/MRI offers huge potential for improving diagnostics in infections of the joints and bones.
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Affiliation(s)
- Kgomotso M G Mokoala
- University of Pretoria, Pretoria, Gauteng, South Africa; Nuclear Medicine Research Infrastructure (NuMeRI), Pretoria, Gauteng, South Africa
| | - Honest Ndlovu
- Nuclear Medicine Research Infrastructure (NuMeRI), Pretoria, Gauteng, South Africa
| | - Ismaheel Lawal
- University of Pretoria, Pretoria, Gauteng, South Africa; Emory University, Atlanta, Georgia, United States
| | - Mike Machaba Sathekge
- University of Pretoria, Pretoria, Gauteng, South Africa; Nuclear Medicine Research Infrastructure (NuMeRI), Pretoria, Gauteng, South Africa.
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Mitra JB, Mukherjee A, Kumar A, Chandak A, Rakshit S, Yadav HD, Pandey BN, Sarma HD. Imaging of bacterial infection: Harnessing positron emission tomography and Cherenkov luminescence imaging with UBI-derived octapeptide. Drug Dev Res 2023; 84:1513-1521. [PMID: 37571805 DOI: 10.1002/ddr.22103] [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] [Received: 05/22/2023] [Revised: 07/07/2023] [Accepted: 08/01/2023] [Indexed: 08/13/2023]
Abstract
Noninvasive imaging techniques for the early detection of infections are in high demand. In this study, we present the development of an infection imaging agent consisting of the antimicrobial peptide fragment UBI (31-38) conjugated to the chelator 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA), which allows for labeling with the positron emitter Ga-68. The preclinical evaluation of [68 Ga]Ga-NODAGA-UBI (31-38) was conducted to investigate its potential for imaging bacterial infections caused by Staphylococcus aureus. The octapeptide derived from ubiquicidin, UBI (31-38), was synthesized and conjugated with the chelator NODAGA. The conjugate was then radiolabeled with Ga-68. The radiolabeling process and the stability of the radio formulation were confirmed through chromatography. The study included both in vitro evaluations using S. aureus and in vivo evaluations in an animal model of infection and inflammation. Positron emission tomography (PET) and Cherenkov luminescence imaging (CLI) were performed to visualize the targeted localization of the radio formulation at the site of infection. Ex vivo biodistribution studies were carried out to quantify the uptake of the radio formulation in different organs and tissues. Additionally, the uptake of [18 F]Fluorodeoxyglucose ([18 F] FDG) in the animal model was also studied for comparison. The [68 Ga]Ga-NODAGA-UBI (31-38) complex consistently exhibited high radiochemical purity (>90%) after formulation. The complex demonstrated stability in saline, phosphate-buffered saline, and human serum for up to 3 h. Notably, the complex displayed significantly higher uptake in S. aureus, which was inhibited in the presence of unconjugated UBI (29-41) peptide, confirming the specificity of the formulation for bacterial membranes. Bacterial imaging capability was also observed in PET and CLI images. Biodistribution results indicated a substantial target-to-nontarget ratio of approximately 4 at 1 h postinjection of the radio formulation. Conversely, the uptake of [18 F]FDG in the animal model did not allow for the discrimination of infected and inflamed sites. Our studies have demonstrated that [68 Ga]Ga-NODAGA-UBI (31-38) holds promise as a radiotracer for imaging bacterial infections caused by S. aureus.
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Affiliation(s)
- Jyotsna Bhatt Mitra
- Radiopharmaceuticals Division, Bhabha Atomic Research Centre (BARC), Mumbai, India
- Homi Bhabha National Institute, Mumbai, India
| | - Archana Mukherjee
- Radiopharmaceuticals Division, Bhabha Atomic Research Centre (BARC), Mumbai, India
- Homi Bhabha National Institute, Mumbai, India
| | - Anuj Kumar
- Radiopharmaceuticals Division, Bhabha Atomic Research Centre (BARC), Mumbai, India
| | - Ashok Chandak
- Board of Radiation & Isotope Technology, Navi Mumbai, India
| | - Sutapa Rakshit
- Radiation Medicine Centre, Bhabha Atomic Research Centre (BARC), Mumbai, India
| | - Hansa D Yadav
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre (BARC), Mumbai, India
| | - Badri Narain Pandey
- Homi Bhabha National Institute, Mumbai, India
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre (BARC), Mumbai, India
| | - Haladhar Dev Sarma
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre (BARC), Mumbai, India
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Frei A, Verderosa AD, Elliott AG, Zuegg J, Blaskovich MAT. Metals to combat antimicrobial resistance. Nat Rev Chem 2023; 7:202-224. [PMID: 37117903 PMCID: PMC9907218 DOI: 10.1038/s41570-023-00463-4] [Citation(s) in RCA: 83] [Impact Index Per Article: 83.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/06/2023] [Indexed: 02/10/2023]
Abstract
Bacteria, similar to most organisms, have a love-hate relationship with metals: a specific metal may be essential for survival yet toxic in certain forms and concentrations. Metal ions have a long history of antimicrobial activity and have received increasing attention in recent years owing to the rise of antimicrobial resistance. The search for antibacterial agents now encompasses metal ions, nanoparticles and metal complexes with antimicrobial activity ('metalloantibiotics'). Although yet to be advanced to the clinic, metalloantibiotics are a vast and underexplored group of compounds that could lead to a much-needed new class of antibiotics. This Review summarizes recent developments in this growing field, focusing on advances in the development of metalloantibiotics, in particular, those for which the mechanism of action has been investigated. We also provide an overview of alternative uses of metal complexes to combat bacterial infections, including antimicrobial photodynamic therapy and radionuclide diagnosis of bacterial infections.
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Affiliation(s)
- Angelo Frei
- Community for Open Antimicrobial Drug Discovery, Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia.
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland.
| | - Anthony D Verderosa
- Community for Open Antimicrobial Drug Discovery, Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia
| | - Alysha G Elliott
- Community for Open Antimicrobial Drug Discovery, Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia
| | - Johannes Zuegg
- Community for Open Antimicrobial Drug Discovery, Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia
| | - Mark A T Blaskovich
- Community for Open Antimicrobial Drug Discovery, Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia.
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Marjanovic-Painter B, Kleynhans J, Zeevaart JR, Rohwer E, Ebenhan T. A decade of ubiquicidin development for PET imaging of infection: A systematic review. Nucl Med Biol 2023; 116-117:108307. [PMID: 36435145 DOI: 10.1016/j.nucmedbio.2022.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 10/25/2022] [Accepted: 11/07/2022] [Indexed: 11/15/2022]
Abstract
BACKGROUND Ubiquicidin is a peptide fragment with selective binding to negatively charged bacterial cell membranes. Besides its earlier labelling with gamma emitting radionuclides, it has been labelled with Positron Emission Tomography (PET) radionuclides in the last decade for imaging infection and distinguishing infectious disease from sterile inflammation. This systematic review aims to evaluate the technology readiness level of PET based ubiquicidin radiopharmaceuticals. METHODS Two independent researchers reviewed all articles and abstracts pertaining ubiquicidin and PET imaging that are currently available. Scopus, Google Scholar and PubMed/Medline were used in the search. Upon completion of the literature search all articles and abstracts were evaluated and duplicates were excluded. All non-PET articles as well as review articles without new data were deemed ineligible. RESULTS From a total of 17 papers and 10 abstracts the studies were grouped into development, preclinical and clinical studies. Development was published in 15/17 (88%) publications and 6/10 (60%) abstracts, preclinical applications in 9/17 (53%) publications and 1/10 (10%) of abstracts. Finally, clinical studies made up 6/17 (35%) of full publications and 4/10 (40%) of the available abstracts. Development results were the most abundant. All the findings in the different areas of development of ubiquicidin as PET radiopharmaceutical are summarized in this paper. CONCLUSION Labelling procedures are generally uncomplicated and relatively fast and there are indications of adequate product stability. The production of PET radiopharmaceuticals based on UBI will therefore not be a barrier for clinical introduction of this technology. Systematization and unification of criteria for preclinical imaging and larger clinical trials are needed to ensure the translation of this radiopharmaceutical into the clinic. Therefore a conclusion with regards to the clinical relevance of ubiquicidin based PET is not yet possible.
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Affiliation(s)
| | - Janke Kleynhans
- Nuclear Medicine Research Infrastructure NPC, Pretoria, South Africa
| | - Jan Rijn Zeevaart
- Radiochemistry, The South African Nuclear Energy Corporation, Pelindaba, South Africa; Nuclear Medicine Research Infrastructure NPC, Pretoria, South Africa
| | - Egmont Rohwer
- Department of Chemistry, University of Pretoria, Pretoria, South Africa
| | - Thomas Ebenhan
- Radiochemistry, The South African Nuclear Energy Corporation, Pelindaba, South Africa; Department of Nuclear Medicine, University of Pretoria, Pretoria, South Africa; Nuclear Medicine Research Infrastructure NPC, Pretoria, South Africa.
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Bresser PL, Sathekge MM, Vorster M. PET/CT features of a novel gallium-68 labelled hypoxia seeking agent in patients diagnosed with tuberculosis: a proof-of-concept study. Nucl Med Commun 2022; 43:787-793. [PMID: 35506285 DOI: 10.1097/mnm.0000000000001580] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
INTRODUCTION Positron emission tomography/computed tomography (PET/CT) in infection and inflammation has yielded promising results across a range of radiopharmaceuticals. In particular, PET/CT imaging of tuberculosis (TB) allows for a better understanding of this complex disease by providing insights into molecular processes within the TB microenvironment. TB lesions are hypoxic with research primarily focussed on cellular processes occurring under hypoxic stress. With the development of hypoxia seeking PET/CT radiopharmaceuticals, that can be labelled in-house using a germanium-68/gallium-68 (68Ge/68Ga) generator, a proof-of-concept for imaging hypoxia in TB is presented. METHODS Ten patients diagnosed with TB underwent whole-body PET/CT imaging, 60-90 min after intravenous administration of 74-185 MBq (2-5 mCi) 68Ga-nitroimidazole. No oral or intravenous contrast was administered. Images were visually and semiquantitatively assessed for abnormal 68Ga-uptake in the lungs. RESULTS A total of 28 lesions demonstrating hypoxic uptake were identified. Low- to moderate-uptake was seen in nodules, areas of consolidation and cavitation as well as effusions. The mean standard uptake value (SUVmean) of the lesions was 0.47 (IQR, 0.32-0.82) and SUVmax was 0.71 (IQR, 0.41-1.11). The lesion to muscle ratio (median, 1.70; IQR, 1.15-2.31) was higher than both the left ventricular and the aorta lesion to blood ratios. CONCLUSION Moving towards the development of unique host-directed therapies (HDT), modulation of oxygen levels may improve therapeutic outcome by reprogramming TB lesions to overcome hypoxia. This proof-of-concept study suggests that hypoxia in TB lesions can be imaged and quantified using 68Ga-nitroimidazole PET/CT. Subsequently, hypoxic load can be estimated to inform personalised treatment plans of patients diagnosed with TB.
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Affiliation(s)
- Philippa L Bresser
- Department of Nuclear Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Mike M Sathekge
- Department of Nuclear Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Mariza Vorster
- Department of Nuclear Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Department of Nuclear Medicine, Inkosi Albert Luthuli Central Hospital, University of Kwazulu Natal, Durban, South Africa
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Signore A, Conserva M, Varani M, Galli F, Lauri C, Velikyan I, Roivainen A. PET imaging of bacteria. Nucl Med Mol Imaging 2022. [DOI: 10.1016/b978-0-12-822960-6.00077-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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More S, Marakalala MJ, Sathekge M. Tuberculosis: Role of Nuclear Medicine and Molecular Imaging With Potential Impact of Neutrophil-Specific Tracers. Front Med (Lausanne) 2021; 8:758636. [PMID: 34957144 PMCID: PMC8703031 DOI: 10.3389/fmed.2021.758636] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Accepted: 11/03/2021] [Indexed: 01/02/2023] Open
Abstract
With Tuberculosis (TB) affecting millions of people worldwide, novel imaging modalities and tools, particularly nuclear medicine and molecular imaging, have grown with greater interest to assess the biology of the tuberculous granuloma and evolution thereof. Much early work has been performed at the pre-clinical level using gamma single photon emission computed tomography (SPECT) agents exploiting certain characteristics of Mycobacterium tuberculosis (MTb). Both antituberculous SPECT and positron emission tomography (PET) agents have been utilised to characterise MTb. Other PET tracers have been utilised to help to characterise the biology of MTb (including Gallium-68-labelled radiopharmaceuticals). Of all the tracers, 2-[18F]FDG has been studied extensively over the last two decades in many aspects of the treatment paradigm of TB: at diagnosis, staging, response assessment, restaging, and in potentially predicting the outcome of patients with latent TB infection. Its lower specificity in being able to distinguish different inflammatory cell types in the granuloma has garnered interest in reviewing more specific agents that can portend prognostic implications in the management of MTb. With the neutrophil being a cell type that portends this poorer prognosis, imaging this cell type may be able to answer more accurately questions relating to the tuberculous granuloma transmissivity and may help in characterising patients who may be at risk of developing active TB. The formyl peptide receptor 1(FPR1) expressed by neutrophils is a key marker in this process and is a potential target to characterise these areas. The pre-clinical work regarding the role of radiolabelled N-cinnamoyl –F-(D) L – F – (D) –L F (cFLFLF) (which is an antagonist for FPR1) using Technetium 99m-labelled conjugates and more recently radiolabelled with Gallium-68 and Copper 64 is discussed. It is the hope that further work with this tracer may accelerate its potential to be utilised in responding to many of the current diagnostic dilemmas and challenges in TB management, thereby making the tracer a translatable option in routine clinical care.
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Affiliation(s)
- Stuart More
- Division of Nuclear Medicine, Department of Radiation Medicine, University of Cape Town, Cape Town, South Africa
- Department of Nuclear Medicine, University of Pretoria and Steve Biko Academic Hospital, Pretoria, South Africa
- Nuclear Medicine Research Infrastructure, Steve Biko Academic Hospital, Pretoria, South Africa
- *Correspondence: Stuart More
| | - Mohlopheni J. Marakalala
- Africa Health Research Institute, Durban, South Africa
- Division of Infection and Immunity, University College London, London, United Kingdom
- School of Laboratory Medicine and Medical Sciences, College of Health Sciences, University of KwaZulu-Natal, Durban, South Africa
- Division of Immunology, Department of Pathology, University of Cape Town, Cape Town, South Africa
| | - Michael Sathekge
- Department of Nuclear Medicine, University of Pretoria and Steve Biko Academic Hospital, Pretoria, South Africa
- Nuclear Medicine Research Infrastructure, Steve Biko Academic Hospital, Pretoria, South Africa
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Tegge W, Guerra G, Höltke A, Schiller L, Beutling U, Harmrolfs K, Gröbe L, Wullenkord H, Xu C, Weich H, Brönstrup M. Selective Bacterial Targeting and Infection-Triggered Release of Antibiotic Colistin Conjugates. Angew Chem Int Ed Engl 2021; 60:17989-17997. [PMID: 34097810 PMCID: PMC8456958 DOI: 10.1002/anie.202104921] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 05/28/2021] [Indexed: 12/18/2022]
Abstract
In order to render potent, but toxic antibiotics more selective, we have explored a novel conjugation strategy that includes drug accumulation followed by infection-triggered release of the drug. Bacterial targeting was achieved using a modified fragment of the human antimicrobial peptide ubiquicidin, as demonstrated by fluorophore-tagged variants. To limit the release of the effector colistin only to infection-related situations, we introduced a linker that was cleaved by neutrophil elastase (NE), an enzyme secreted by neutrophil granulocytes at infection sites. The linker carried an optimized sequence of amino acids that was required to assure sufficient cleavage efficiency. The antibacterial activity of five regioisomeric conjugates prepared by total synthesis was masked, but was released upon exposure to recombinant NE when the linker was attached to amino acids at the 1- or the 3-position of colistin. A proof-of-concept was achieved in co-cultures of primary human neutrophils and Escherichia coli that induced the secretion of NE, the release of free colistin, and an antibacterial efficacy that was equal to that of free colistin.
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Affiliation(s)
- Werner Tegge
- Department of Chemical BiologyHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
| | - Giulia Guerra
- Department of Chemical BiologyHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
| | - Alexander Höltke
- Department of Chemical BiologyHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
| | - Lauritz Schiller
- Department of Chemical BiologyHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
| | - Ulrike Beutling
- Department of Chemical BiologyHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
| | - Kirsten Harmrolfs
- Department of Chemical BiologyHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
| | - Lothar Gröbe
- Flow Cytometry and Cell Sorting PlatformHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
| | - Hannah Wullenkord
- Department of Chemical BiologyHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
| | - Chunfa Xu
- Department of Chemical BiologyHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
| | - Herbert Weich
- Department of Chemical BiologyHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
| | - Mark Brönstrup
- Department of Chemical BiologyHelmholtz Centre for Infection ResearchInhoffenstrasse 738124BraunschweigGermany
- German Center for Infection Research (DZIF), SiteHannover-BraunschweigGermany
- Center of Biomolecular Drug Research (BMWZ)Leibniz Universität30167HannoverGermany
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Tegge W, Guerra G, Höltke A, Schiller L, Beutling U, Harmrolfs K, Gröbe L, Wullenkord H, Xu C, Weich H, Brönstrup M. Zielgerichtete bakterielle Lokalisation und infektionsinduzierte Freisetzung von antibiotischen Colistin‐Konjugaten. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202104921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Werner Tegge
- Abteilung für Chemische Biologie Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
| | - Giulia Guerra
- Abteilung für Chemische Biologie Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
| | - Alexander Höltke
- Abteilung für Chemische Biologie Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
| | - Lauritz Schiller
- Abteilung für Chemische Biologie Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
| | - Ulrike Beutling
- Abteilung für Chemische Biologie Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
| | - Kirsten Harmrolfs
- Abteilung für Chemische Biologie Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
| | - Lothar Gröbe
- Flow Cytometry and Cell Sorting Platform Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
| | - Hannah Wullenkord
- Abteilung für Chemische Biologie Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
| | - Chunfa Xu
- Abteilung für Chemische Biologie Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
| | - Herbert Weich
- Abteilung für Chemische Biologie Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
| | - Mark Brönstrup
- Abteilung für Chemische Biologie Helmholtz-Zentrum für Infektionsforschung Inhoffenstraße 7 38124 Braunschweig Deutschland
- Deutsches Zentrum für Infektionsforschung (DZIF), Standort Hannover-Braunschweig Deutschland
- Biomolekulares Wirkstoffzentrum (BMWZ) Leibniz Universität 30167 Hannover Deutschland
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Welling MM, Duszenko N, van Willigen DM, Hensbergen AW, Buckle T, Rietbergen DDD, Roestenberg M, van Leeuwen FWB. Interventional nuclear medicine: "click" chemistry as an in vivo targeting strategy for imaging microspheres and bacteria. Biomater Sci 2021; 9:1683-1690. [PMID: 33410436 DOI: 10.1039/d0bm01823f] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
AIM Pre-targeting is a proven strategy for in vivo delivery of a diagnostic or therapeutic payload. The pre-targeting concept can be realized through various conjugation strategies, one of which is based on copper-free "click" chemistry. Copper-free click reactions have shown in vivo potential for imaging and radionuclide therapy, but this conjugation strategy has not yet been explored in combination with microspheres or unicellular organisms. This study aims to evaluate the in vivo efficacy of strain-promoted azide-alkyne cycloaddition (SPAAC) reactions to achieve imaging and targeting of azide-functionalized macro-aggregated albumin (MAA) microspheres and Staphylococcus aureus bacteria. METHODS MAA microspheres (diameter 10-90 μm) were functionalized with a biorthogonal Cy5 fluorophore, bearing an azide functionality (N3), to generate MAA-Cy5-N3. S. aureus (diameter ∼1 μm) were functionalized with 99mTc-UBI29-41-Cy5-N3, generating S. aureus-99mTc-UBI29-41-Cy5-N3. In situ and in vitro click conjugation on the -N3 moieties was studied for 20 h using a radioactivity-based assay and fluorescence microscopy. For in vivo validation, both primary entities, radiolabeled with 99mTc, were deposited into the microvasculature of the liver via intrasplenic injections. Secondary targeting was realized following the intravenous administration of indium-111-radiolabeled diethylenetriaminepentaacetic acid-dibenzocyclooctyne (111In-DTPA-DBCO). To assess click reaction efficiency in vivo, 99mTc and 111In-biodistributions were measured (SPECT and %ID g-1). Use of 111In-DTPA-DBCO in mice without MAA deposits or mice infected with non-functionalized S. aureus served as controls. Ex vivo confocal fluorescence imaging was carried out in excised tissues to confirm the presence of functionalized MAA and bacteria. RESULTS In vitro data confirmed effective click reactions on both the MAA particles and the bacterial membrane. SPECT imaging and biodistribution studies revealed significantly (p < 0.05) increased accumulation of 111In-DTPA-DBCO at the sites where MAA-Cy5-N3 (7.5 ± 1.5%ID g-1vs. 3.5 ± 0.5%ID g-1 in control mice) and S. aureus-99mTc-UBI29-41-Cy5-N3 (9.3 ± 1.3%ID g-1vs. 6.0 ± 0.5%ID g-1 in control mice) resided. Ex vivo fluorescence imaging confirmed the presence of either functionalized MAA or S. aureus in excised spleens and livers of mice. CONCLUSION Copper-free click chemistry between a DBCO moiety and Cy5-N3-functionalized microspheres or bacterial entities in the liver can be used to realize in vivo imaging and targeting.
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Affiliation(s)
- M M Welling
- Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC, Leiden, Netherlands.
| | - N Duszenko
- Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC, Leiden, Netherlands. and Departments of Parasitology and Infectious Diseases, Leiden University Medical Center, Leiden, Netherlands
| | - D M van Willigen
- Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC, Leiden, Netherlands.
| | - A W Hensbergen
- Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC, Leiden, Netherlands.
| | - T Buckle
- Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC, Leiden, Netherlands.
| | - D D D Rietbergen
- Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC, Leiden, Netherlands. and Section of Nuclear Medicine, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - M Roestenberg
- Departments of Parasitology and Infectious Diseases, Leiden University Medical Center, Leiden, Netherlands
| | - F W B van Leeuwen
- Interventional Molecular Imaging Laboratory, Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC, Leiden, Netherlands.
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Recent Progress in the Molecular Imaging of Tumor-Treating Bacteria. Nucl Med Mol Imaging 2021; 55:7-14. [PMID: 33643484 DOI: 10.1007/s13139-021-00689-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Revised: 01/13/2021] [Accepted: 01/20/2021] [Indexed: 12/20/2022] Open
Abstract
Bacterial cancer therapy (BCT) approaches have been extensively investigated because bacteria can show unique features of strong tropism for cancer, proliferation inside tumors, and antitumor immunity, while bacteria are also possible agents for drug delivery. Despite the rapidly increasing number of preclinical studies using BCT to overcome the limitations of conventional cancer treatments, very few BCT studies have advanced to clinical trials. In patients undergoing BCT, the precise localization and quantification of bacterial density in different body locations is important; however, most clinical trials have used subjective clinical signs and invasive sampling to confirm bacterial colonization. There is therefore a need to improve the visualization of bacterial densities using noninvasive and repetitive in vivo imaging techniques that can facilitate the clinical translation of BCT. In vivo optical imaging techniques using bioluminescence and fluorescence, which are extensively employed to image the therapeutic process of BCT in small animal research, are hard to apply to the human body because of their low penetrative power. Thus, new imaging techniques need to be developed for clinical trials. In this review, we provide an overview of the various in vivo bacteria-specific imaging techniques available for visualizing tumor-treating bacteria in BCT studies.
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Kumar N, Roopa, Bhalla V, Kumar M. Beyond zinc coordination: Bioimaging applications of Zn(II)-complexes. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2020.213550] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Ordoñez AA, Jain SK. Imaging of Bacterial Infections. Mol Imaging 2021. [DOI: 10.1016/b978-0-12-816386-3.00089-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Gunzer M, Thornton CR, Beziere N. Advances in the In Vivo Molecular Imaging of Invasive Aspergillosis. J Fungi (Basel) 2020; 6:jof6040338. [PMID: 33291706 PMCID: PMC7761943 DOI: 10.3390/jof6040338] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 12/01/2020] [Accepted: 12/02/2020] [Indexed: 02/07/2023] Open
Abstract
Invasive pulmonary aspergillosis (IPA) is a life-threatening infection of immunocompromised patients with Aspergillus fumigatus, a ubiquitous environmental mould. While there are numerous functioning antifungal therapies, their high cost, substantial side effects and fear of overt resistance development preclude permanent prophylactic medication of risk-patients. Hence, a fast and definitive diagnosis of IPA is desirable, to quickly identify those patients that really require aggressive antimycotic treatment and to follow the course of the therapeutic intervention. However, despite decades of research into this issue, such a diagnostic procedure is still not available. Here, we discuss the array of currently available methods for IPA detection and their limits. We then show that molecular imaging using positron emission tomography (PET) combined with morphological computed tomography or magnetic imaging is highly promising to become a future non-invasive approach for IPA diagnosis and therapy monitoring, albeit still requiring thorough validation and relying on further acceptance and dissemination of the approach. Thereby, our approach using the A. fumigatus-specific humanized monoclonal antibody hJF5 labelled with 64Cu as PET-tracer has proven highly effective in pre-clinical models and hence bears high potential for human application.
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Affiliation(s)
- Matthias Gunzer
- Institute for Experimental Immunology and Imaging, University Hospital, University Duisburg-Essen, 45147 Essen, Germany
- Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., 44227 Dortmund, Germany
- Correspondence: (M.G.); (N.B.); Tel.: +49-201-183-6640 (M.G.); +49-7071-29-87511 (N.B.)
| | - Christopher R. Thornton
- ISCA Diagnostics Ltd. and Biosciences, College of Life & Environmental Sciences, University of Exeter, Exeter EX4 4PY, UK;
| | - Nicolas Beziere
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tübingen, 72076 Tübingen, Germany
- Correspondence: (M.G.); (N.B.); Tel.: +49-201-183-6640 (M.G.); +49-7071-29-87511 (N.B.)
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Welling MM, Hensbergen AW, Bunschoten A, Velders AH, Scheper H, Smits WK, Roestenberg M, van Leeuwen FWB. Fluorescent imaging of bacterial infections and recent advances made with multimodal radiopharmaceuticals. Clin Transl Imaging 2019. [DOI: 10.1007/s40336-019-00322-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Bhatt J, Mukherjee A, Shinto A, Koramadai Karuppusamy K, Korde A, Kumar M, Sarma HD, Repaka K, Dash A. Gallium-68 labeled Ubiquicidin derived octapeptide as a potential infection imaging agent. Nucl Med Biol 2018; 62-63:47-53. [PMID: 29883883 DOI: 10.1016/j.nucmedbio.2018.04.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 03/23/2018] [Accepted: 04/27/2018] [Indexed: 10/17/2022]
Abstract
INTRODUCTION Gallium-68 based infection imaging agents are in demand to detect infection foci with high spatial resolution and sensitivity. In this study, Ubiquicidin derived octapeptide, UBI (31-38) conjugated with macrocyclic chelator NOTA was radiolabeled with 68Ga to develop infection imaging agent. METHODS Circular dichroism (CD) spectroscopy was performed to study conformational changes in UBI (31-38) and its NOTA conjugate in a "membrane like environment". Radiolabeling of NOTA-UBI (31-38) with 68Ga was optimized and quality control analysis was done by chromatography techniques. In vitro evaluation of 68Ga-NOTA-UBI (31-38) in S. aureus and preliminary biological evaluation in animal model of infection was studied. Initial clinical evaluation in three patients with suspected infection was carried out. RESULTS 68Ga-NOTA-UBI (31-38) was prepared in high radiochemical yields and high radiochemical purity. In vitro evaluation of 68Ga-NOTA-UBI (31-38) complex in S. aureus confirmed specificity of the agent for bacteria. Biodistribution studies with 68Ga-NOTA-UBI (31-38) revealed specific uptake of the complex in infected muscle compared to inflamed muscle with T/NT ratio of 3.24 ± 0.7 at 1 h post-injection. Initial clinical evaluation in two patients with histopathologically confirmed infective foci conducted after intravenous injection of 130-185 MBq of 68Ga-NOTA-UBI (31-38) and imaging at 45-60 min post-injection revealed specific uptake at the sites of infection and clearance from vital organs. No uptake of tracer was observed in suspected infection foci in one patient, which was proven to be aseptic and served as negative control. CONCLUSION This is the first report on 68Ga labeled NOTA-UBI (31-38) fragment for prospective infection imaging.
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Affiliation(s)
- Jyotsna Bhatt
- Radiopharmaceuticals Division, Bhabha Atomic Research Centre (BARC), Mumbai 400085, India; Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Archana Mukherjee
- Radiopharmaceuticals Division, Bhabha Atomic Research Centre (BARC), Mumbai 400085, India; Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India.
| | - Ajit Shinto
- Dept of Nuclear Medicine and PET-CT, Kovai Medical Center and Hospital Limited, Coimbatore, India
| | | | - Aruna Korde
- Radiopharmaceuticals Division, Bhabha Atomic Research Centre (BARC), Mumbai 400085, India; Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India; Quality control, Board of Radiation and Isotope Technology, Vashi, Navi Mumbai, India
| | - Mukesh Kumar
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre (BARC), Mumbai 400085, India; Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Haladhar Dev Sarma
- Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre (BARC), Mumbai 400085, India
| | - Krishnamohan Repaka
- Quality control, Board of Radiation and Isotope Technology, Vashi, Navi Mumbai, India
| | - Ashutosh Dash
- Radiopharmaceuticals Division, Bhabha Atomic Research Centre (BARC), Mumbai 400085, India; Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
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Ordonez AA, Jain SK. Pathogen-Specific Bacterial Imaging in Nuclear Medicine. Semin Nucl Med 2018. [DOI: 10.1053/j.semnuclmed.2017.11.003
expr 890398765 + 809902709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
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Abstract
When serious infections are suspected, patients are often treated empirically with broad-spectrum antibiotics while awaiting results that provide information on the bacterial class and species causing the infection, as well as drug susceptibilities. For deep-seated infections, these traditional diagnostic techniques often rely on tissue biopsies to obtain clinical samples which can be expensive, dangerous, and has the potential of sampling bias. Moreover, these procedures and results can take several days and may not always provide reliable information. This combination of time and effort required for proper antibiotic selection has become a barrier leading to indiscriminate broad-spectrum antibiotic use. Exposure to nosocomial infections and indiscriminate use of broad-spectrum antibiotics are responsible for promoting bacterial drug-resistance leading to substantial morbidity and mortality, especially in hospitalized and immunosuppressed patients. Therefore, early diagnosis of infection and targeted antibiotic treatments are urgently needed to reduce morbidity and mortality caused by bacterial infections worldwide. Reliable pathogen-specific bacterial imaging techniques have the potential to provide early diagnosis and guide antibiotic treatments.
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Affiliation(s)
- Alvaro A Ordonez
- Center for Infection and Inflammation Imaging Research, Johns Hopkins University School of Medicine, Baltimore, MD; Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Sanjay K Jain
- Center for Infection and Inflammation Imaging Research, Johns Hopkins University School of Medicine, Baltimore, MD; Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD.
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Prospective of 68Ga Radionuclide Contribution to the Development of Imaging Agents for Infection and Inflammation. CONTRAST MEDIA & MOLECULAR IMAGING 2018. [PMID: 29531507 PMCID: PMC5817300 DOI: 10.1155/2018/9713691] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
During the last decade, the utilization of 68Ga for the development of imaging agents has increased considerably with the leading position in the oncology. The imaging of infection and inflammation is lagging despite strong unmet medical needs. This review presents the potential routes for the development of 68Ga-based agents for the imaging and quantification of infection and inflammation in various diseases and connection of the diagnosis to the treatment for the individualized patient management.
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Romero Pastrana F, Thompson JM, Heuker M, Hoekstra H, Dillen CA, Ortines RV, Ashbaugh AG, Pickett JE, Linssen MD, Bernthal NM, Francis KP, Buist G, van Oosten M, van Dam GM, Thorek DLJ, Miller LS, van Dijl JM. Noninvasive optical and nuclear imaging of Staphylococcus-specific infection with a human monoclonal antibody-based probe. Virulence 2017; 9:262-272. [PMID: 29166841 PMCID: PMC5955194 DOI: 10.1080/21505594.2017.1403004] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Staphylococcus aureus infections are a major threat in healthcare, requiring adequate early-stage diagnosis and treatment. This calls for novel diagnostic tools that allow noninvasive in vivo detection of staphylococci. Here we performed a preclinical study to investigate a novel fully-human monoclonal antibody 1D9 that specifically targets the immunodominant staphylococcal antigen A (IsaA). We show that 1D9 binds invariantly to S. aureus cells and may further target other staphylococcal species. Importantly, using a human post-mortem implant model and an in vivo murine skin infection model, preclinical feasibility was demonstrated for 1D9 labeled with the near-infrared fluorophore IRDye800CW to be applied for direct optical imaging of in vivo S. aureus infections. Additionally, 89Zirconium-labeled 1D9 could be used for positron emission tomography imaging of an in vivo S. aureus thigh infection model. Our findings pave the way towards clinical implementation of targeted imaging of staphylococcal infections using the human monoclonal antibody 1D9.
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Affiliation(s)
- Francisco Romero Pastrana
- a Department of Medical Microbiology , University of Groningen, University Medical Center Groningen , Hanzeplein 1, Groningen , RB , The Netherlands
| | - John M Thompson
- b Department of Orthopaedic Surgery , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Marjolein Heuker
- a Department of Medical Microbiology , University of Groningen, University Medical Center Groningen , Hanzeplein 1, Groningen , RB , The Netherlands
| | - Hedzer Hoekstra
- a Department of Medical Microbiology , University of Groningen, University Medical Center Groningen , Hanzeplein 1, Groningen , RB , The Netherlands
| | - Carly A Dillen
- c Department of Dermatology , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Roger V Ortines
- c Department of Dermatology , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Alyssa G Ashbaugh
- c Department of Dermatology , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Julie E Pickett
- d Division of Nuclear Medicine and Molecular Imaging, Department of Radiology and Radiological Science , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Matthijs D Linssen
- e Department of Gastroentrology and Hepatology , University of Groningen, University Medical Center Groningen , Hanzeplein 1, Groningen , RB , The Netherlands.,f Department of clinical Pharmacy and Pharmacology , University of Groningen, University Medical Center Groningen , Hanzeplein 1, Groningen , RB , The Netherlands
| | - Nicholas M Bernthal
- g Department of Orthopaedic Surgery , David Geffen School of Medicine at the University of California, Los Angeles Medical Center , Santa Monica , CA , USA
| | - Kevin P Francis
- g Department of Orthopaedic Surgery , David Geffen School of Medicine at the University of California, Los Angeles Medical Center , Santa Monica , CA , USA.,h PerkinElmer , Alameda , California , CA , USA.,i Department of Surgery , Nuclear Medicine and Molecular Imaging and Intensive Care, University of Groningen, University Medical Center Groningen , Hanzeplein 1, Groningen , RB , The Netherlands
| | - Girbe Buist
- a Department of Medical Microbiology , University of Groningen, University Medical Center Groningen , Hanzeplein 1, Groningen , RB , The Netherlands
| | - Marleen van Oosten
- a Department of Medical Microbiology , University of Groningen, University Medical Center Groningen , Hanzeplein 1, Groningen , RB , The Netherlands
| | - Gooitzen M van Dam
- i Department of Surgery , Nuclear Medicine and Molecular Imaging and Intensive Care, University of Groningen, University Medical Center Groningen , Hanzeplein 1, Groningen , RB , The Netherlands
| | - Daniel L J Thorek
- d Division of Nuclear Medicine and Molecular Imaging, Department of Radiology and Radiological Science , Johns Hopkins University School of Medicine , Baltimore , MD , USA.,j Department of Oncology , Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Lloyd S Miller
- b Department of Orthopaedic Surgery , Johns Hopkins University School of Medicine , Baltimore , MD , USA.,c Department of Dermatology , Johns Hopkins University School of Medicine , Baltimore , MD , USA.,k Division of Infectious Disease, Department of Medicine , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Jan Maarten van Dijl
- a Department of Medical Microbiology , University of Groningen, University Medical Center Groningen , Hanzeplein 1, Groningen , RB , The Netherlands
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Molecular imaging in musculoskeletal infections with 99mTc-UBI 29-41 SPECT/CT. Ann Nucl Med 2017; 32:54-59. [PMID: 29164482 DOI: 10.1007/s12149-017-1219-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 11/16/2017] [Indexed: 12/16/2022]
Abstract
OBJECTIVE To determine the added value of CT over planar and SPECT-only imaging in the diagnosis of musculoskeletal infection using 99mTc-UBI 29-4. MATERIALS AND METHODS 184 patients with suspected musculoskeletal infection who underwent planar and SPECT/CT imaging with 99mTc-UBI 29-41 were included. Planar, SPECT-only and SPECT/CT images were reviewed by two independent analysts for presence of bone or soft tissue infection. Final diagnosis was confirmed with tissue cultures, surgery/histology or clinical follow-up. RESULTS 99mTc-UBI 29-41 was true positive in 105/184 patients and true negative in 65/184 patients. When differentiating between soft tissue and bone infection, planar + SPECT-only imaging had a sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 95.0, 74.3, 84.8, 91.3 and 86.9%, respectively, versus 99.0, 94.5, 92.5, 98.5 and 94.5% for SPECT/CT. SPECT/CT resulted in a change in reviewers' confidence in the final diagnosis in 91/184 patients. Inter-observer agreement was better with SPECT/CT compared with planar + SPECT imaging (kappa 0.87, 95% CI 0.71-0.85 versus kappa 0.81, 95% CI 0.58-0.75). CONCLUSION Addition of CT to planar and SPECT-only imaging led to an increase in diagnostic performance and an improvement in reviewers' confidence and inter-observer agreement in differentiating bone from soft tissue infection.
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