Acinetobacter baumannii (AB) is an opportunistic pathogen with growing clinical relevance due to its increasing level of antimicrobial resistance in the last few decades. In the event of an AB hospital outbreak, fast detection and localization of the pathogen is crucial, to prevent its further spread. However, contemporary diagnostic tools do not always meet the requirements for rapid and accurate diagnosis. For this reason, we report here the possibility of using gallium-68 labeled siderophores, bacterial iron chelators, for positron emission tomography imaging of AB infections. In our study, we radiolabeled several siderophores and tested their in vitro uptake in AB cultures. Based on the results and the in vitro properties of studied siderophores, we selected two of them for further in vivo testing in infectious models. Both selected siderophores, ferrioxamine E and ferrirubin, showed promising in vitro characteristics. In vivo, we observed rapid pharmacokinetics and no excessive accumulation in organs other than the excretory organs in normal mice. We demonstrated that the radiolabeled siderophores accumulate in AB-infected tissue in three animal models: a murine model of myositis, a murine model of dorsal wound infection and a rat model of pneumonia. These results suggest that both siderophores radiolabeled with Ga-68 could be used for PET imaging of AB infection.

• Klíčová slova
• Acinetobacter baumannii, PET, gallium-68, radiolabeling, siderophores,
• MeSH
• Acinetobacter baumannii * MeSH
• infekce bakteriemi rodu Acinetobacter * diagnostické zobrazování   mikrobiologie   MeSH
• krysa rodu Rattus MeSH
• modely nemocí na zvířatech MeSH
• myši MeSH
• pozitronová emisní tomografie * metody   MeSH
• radioizotopy galia * chemie   MeSH
• siderofory * chemie   farmakokinetika   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• srovnávací studie MeSH
• Názvy látek
• Gallium-68 MeSH Prohlížeč
• radioizotopy galia * MeSH
• siderofory * MeSH

Background/Objectives: PET imaging of bacterial infection could potentially provide added benefits for patient care through non-invasive means. [68Ga]Ga-desferrioxamine B-a radiolabelled siderophore-shows specific uptake by human-pathogenic bacteria like Staphylococcus aureus or Pseudomonas aeruginosa and sufficient serum stability for clinical application. In this report, we present data for automated production of [68Ga]Ga-desferrioxamine B on two different cassette-based synthesis modules (Modular-Lab PharmTracer and GRP 3V) utilising commercially obtainable cassettes together with a licensed 68Ge/68Ga radionuclide generator. Methods: Quality control, including the determination of radiochemical purity, as well as a system suitability test, was set up via RP-HPLC on a C18 column. The two described production processes use an acetic acid/acetate buffer system with ascorbic acid as a radical scavenger for radiolabelling, yielding ready-to-use formulations with sufficient activity yield. Results: Batch data analysis demonstrated radiochemical purity of >95% by RP-HPLC combined with ITLC and excellent stability up to 2 h after synthesis. Specifications for routine production were set up and validated with four masterbatches for each synthesis module. Conclusions: Based on this study, an academic clinical trial for imaging of bacterial infection was initiated. Both described synthesis methods enable automated production of [68Ga]Ga-desferrioxamine B in-house with high reproducibility for clinical application.

• Klíčová slova
• PET, desferrioxamine B, gallium-68, imaging, infection, validation,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: Siderophores are small iron-binding molecules produced by microorganisms to facilitate iron acquisition from the environment. Radiolabelled siderophores offer a promising solution for infection imaging, as they can specifically target the pathophysiological mechanisms of pathogens. Gallium-68 can replace the iron in siderophores, enabling molecular imaging with positron emission tomography (PET). Stereospecific interactions play a crucial role in the recognition of receptors, transporters, and iron utilisation. Furthermore, these interactions have an impact on the host environment, affecting pharmacokinetics and biodistribution. This study examines the influence of siderophore stereoisomerism on imaging properties, with a focus on ferrirubin (FR) and ferrirhodin (FRH), two cis-trans isomeric siderophores of the ferrichrome type. RESULTS: Tested siderophores were labelled with gallium-68 with high radiochemical purity. The resulting complexes differed in their in vitro characteristics. [68Ga]Ga-FRH showed less hydrophilic properties and higher protein binding values than [68Ga]Ga-FR. The stability studies confirmed the high radiochemical stability of both [68Ga]Ga-siderophores in all examined media. Both siderophores were found to be taken up by S. aureus, K. pneumoniae and P. aeruginosa with similar efficacy. The biodistribution tested in normal mice showed rapid renal clearance with low blood pool retention and fast clearance from examined organs for [68Ga]Ga-FR, whereas [68Ga]Ga-FRH showed moderate retention in blood, resulting in slower pharmacokinetics. PET/CT imaging of mice injected with [68Ga]Ga-FR and [68Ga]Ga-FRH confirmed findings from ex vivo biodistribution studies. In a mouse model of S. aureus myositis, both radiolabeled siderophores showed radiotracer accumulation at the site of infection. CONCLUSIONS: The 68Ga-complexes of stereoisomers ferrirubin and ferrirhodin revealed different pharmacokinetic profiles. In vitro uptake was not affected by isomerism. Both compounds had uptake with the same bacterial culture with similar efficacy. PET/CT imaging showed that the [68Ga]Ga-complexes accumulate at the site of S. aureus infection, highlighting the potential of [68Ga]Ga-FR as a promising tool for infection imaging. In contrast, retention of the radioactivity in the blood was observed for [68Ga]Ga-FRH. In conclusion, the stereoisomerism of potential radiotracers should be considered, as even minor structural differences can influence their pharmacokinetics and, consequently, the results of PET imaging.

• Klíčová slova
• Imaging, Infection, Positron emission tomography, Siderophore, Stereoisomers,
• Publikační typ
• časopisecké články MeSH

Invasive fungal infections have become a major challenge for public health, mainly due to the growing numbers of immunocompromised patients, with high morbidity and mortality. Currently, conventional imaging modalities such as computed tomography and magnetic resonance imaging contribute largely to the noninvasive diagnosis and treatment evaluation of those infections. These techniques, however, often fall short when a fast, noninvasive and specific diagnosis of fungal infection is necessary. Molecular imaging, especially using nuclear medicine-based techniques, aims to develop fungal-specific radiotracers that can be tested in preclinical models and eventually translated to human applications. In the last few decades, multiple radioligands have been developed and tested as potential fungal-specific tracers. These include radiolabeled peptides, antifungal drugs, siderophores, fungal-specific antibodies, and sugars. In this review, we provide an overview of the pros and cons of the available radiotracers. We also address the future prospects of fungal-specific imaging.

• Klíčová slova
• PET, immunoPET, invasive fungal infection, radionuclide imaging, siderophores,
• MeSH
• antifungální látky terapeutické užití   MeSH
• invazivní mykotické infekce * MeSH
• lidé MeSH
• mykózy * diagnostické zobrazování   MeSH
• počítačová rentgenová tomografie MeSH
• pozitronová emisní tomografie metody   MeSH
• protilátky fungální MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Research Support, N.I.H., Intramural MeSH
• Názvy látek
• antifungální látky MeSH
• protilátky fungální MeSH

Bacteria from the Burkholderia cepacia complex are generally considered to be non-pathogenic to the healthy population. However, some of these species may cause serious nosocomial infections in immunocompromised patients; as such, it is essential to diagnose these infections rapidly so that adequate treatment can be initiated. We report here the use of a radiolabeled siderophore, ornibactin (ORNB), for positron emission tomography imaging. We successfully radiolabeled ORNB with gallium-68 with high radiochemical purity and proved that the resulting complex has optimal in vitro characteristics. In mice, the complex did not show excessive accumulation in organs and was excreted in the urine. We demonstrated that the [68Ga]Ga-ORNB complex accumulates at the site of Burkholderia multivorans infection, including pneumonia, in two animal infection models. These results suggest that [68Ga]Ga-ORNB is a promising tool for the diagnosis, monitoring, and evaluation of the therapeutic response to B. cepacia complex infection.

• MeSH
• Burkholderia cepacia komplex * MeSH
• infekce bakteriemi rodu Burkholderia * diagnostické zobrazování   epidemiologie   MeSH
• myši MeSH
• pozitronová emisní tomografie MeSH
• radioizotopy galia MeSH
• siderofory MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• radioizotopy galia MeSH
• siderofory MeSH

Fungal infections are a serious threat, especially for immunocompromised patients. Early and reliable diagnosis is crucial to treat such infections. The bacterially produced siderophore desferrioxamine B (DFO-B) is utilized by a variety of microorganisms for iron acquisition, while mammalian cells lack the uptake of DFO-B chelates. DFO-B is clinically approved for a variety of long-term chelation therapies. Recently, DFO-B-complexed gallium-68 ([68Ga]Ga-DFO-B) was shown to enable molecular imaging of bacterial infections by positron emission tomography (PET). Here, we demonstrate that [68Ga]Ga-DFO-B can also be used for the preclinical molecular imaging of pulmonary infection caused by the fungal pathogen Aspergillus fumigatus in a rat aspergillosis model. Moreover, by combining in vitro uptake studies and the chemical modification of DFO-B, we show that the cellular transport efficacy of ferrioxamine-type siderophores is impacted by the charge of the molecule and, consequently, the environmental pH. The chemical derivatization has potential implications for its diagnostic use and characterizes transport features of ferrioxamine-type siderophores.

• Klíčová slova
• Aspergillus fumigatus, PET, desferrioxamine B, gallium-68, imaging, infection, invasive pulmonary aspergillosis, pH, positron emission tomography, siderophore,
• Publikační typ
• časopisecké články MeSH

In acutely ill patients, particularly in intensive care units or in mixed infections, time to a microbe-specific diagnosis is critical to a successful outcome of therapy. We report the application of evolving technologies involving mass spectrometry to diagnose and monitor a patient's course. As proof of this concept, we studied five patients and used two rat models of mono-infection and coinfection. We report the noninvasive combined monitoring of Aspergillus fumigatus and Pseudomonas aeruginosa infection. The invasive coinfection was detected by monitoring the fungal triacetylfusarinine C and ferricrocin siderophore levels and the bacterial metabolites pyoverdin E, pyochelin, and 2-heptyl-4-quinolone, studied in the urine, endotracheal aspirate, or breath condensate. The coinfection was monitored by mass spectrometry followed by isotopic data filtering. In the rat infection model, detection indicated 100-fold more siderophores in urine compared to sera, indicating the diagnostic potential of urine sampling. The tools utilized in our studies can now be examined in large clinical series, where we could expect the accuracy and speed of diagnosis to be competitive with conventional methods and provide advantages in unraveling the complexities of mixed infections.

• Klíčová slova
• Aspergillus fumigatus, Pseudomonas aeruginosa, coinfection, invasive infection, noninvasive diagnosis, quorum-sensing molecules, siderophores, virulence factor,
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH

Angiogenesis has a pivotal role in tumor growth and the metastatic process. Molecular imaging was shown to be useful for imaging of tumor-induced angiogenesis. A great variety of radiolabeled peptides have been developed to target αvβ3 integrin, a target structure involved in the tumor-induced angiogenic process. The presented study aimed to synthesize deferoxamine (DFO)-based c(RGD) peptide conjugate for radiolabeling with gallium-68 and perform its basic preclinical characterization including testing of its tumor-imaging potential. DFO-c(RGDyK) was labeled with gallium-68 with high radiochemical purity. In vitro characterization including stability, partition coefficient, protein binding determination, tumor cell uptake assays, and ex vivo biodistribution as well as PET/CT imaging was performed. [68Ga]Ga-DFO-c(RGDyK) showed hydrophilic properties, high stability in PBS and human serum, and specific uptake in U-87 MG and M21 tumor cell lines in vitro and in vivo. We have shown here that [68Ga]Ga-DFO-c(RGDyK) can be used for αvβ3 integrin targeting, allowing imaging of tumor-induced angiogenesis by positron emission tomography.

• Klíčová slova
• PET imaging, RGD peptides, deferoxamine, integrins, radiodiagnostics,
• MeSH
• deferoxamin analogy a deriváty   chemická syntéza   chemie   MeSH
• glioblastom diagnostické zobrazování   MeSH
• integrin alfaVbeta3 metabolismus   MeSH
• lidé MeSH
• myši inbrední BALB C MeSH
• myši nahé MeSH
• myši MeSH
• nádorové buněčné linie MeSH
• patologická angiogeneze diagnostické zobrazování   MeSH
• počítačová rentgenová tomografie metody   MeSH
• pozitronová emisní tomografie metody   MeSH
• radioizotopy galia chemie   MeSH
• tkáňová distribuce MeSH
• transplantace heterologní MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• deferoxamin MeSH
• Gallium-68 MeSH Prohlížeč
• integrin alfaVbeta3 MeSH
• radioizotopy galia MeSH