An update on radiotracer development for molecular imaging of bacterial infections

Background: Bacterial infections are still a major global healthcare problem. To combat the increasing antimicrobial resistance, early diagnosis of bacterial infections—including the identification of bacterial species—is needed to improve antibiotic stewardship and to help reduce the use of broad-spectrum antibiotics. To aid successful targeted antibiotic treatment, specific detection and localisation of infectious organisms is warranted. Nuclear medicine imaging approaches have been successfully used to diagnose bacterial infections and to differentiate between pathogen induced infections and sterile inflammatory processes. Aim: In this comprehensive review we present an overview of recent developments in radiolabelled bacterial imaging tracers. Methods: The PubMed/MEDLINE and Embase (OvidSP) literature databases were systematically searched for publications on SPECT and PET on specific imaging of bacterial using specific guidelines with MeSH-terms, truncations, and completion using cross-references. Tracers in literature that was extensively reviewed before 2016 were not included in this update. Where possible, the chemical structure of the radiolabelled compounds and clinical images were shown. Results: In 219 original articles pre-clinical and clinical imaging of bacterial infection with new tracers were included. In our view, the highest translational potential lies with tracers that are specific to target the pathogens: e.g., ^99m Tc- and ⁶⁸ Ga-labelled UBI _29–41 , ^99m Tc-vancomycin, m-[ ¹⁸ F]-fluoro-PABA, [methyl- ¹¹ C]-D-methionine, [ ¹⁸ F]-FDS, [ ¹⁸ F]-maltohexaose and [ ¹⁸ F]-maltotriose. An encouraging note is that some of these tracers have already been successfully evaluated in clinical settings. Conclusion: This review summarises updates in tracer development for specific (pre-clinical and clinical) imaging of bacterial infections. We propsed some promising tracers that are likely to become innovative standards in the clinical setting in the near feature.