Specific Imaging of bacterial infection with PET – challenges and opportunities

Life-threatening bacterial infections such as vascular graft infections, endocarditis or sepsis often have a non-specific clinical presentation. The differentiation of inflammation due to bacterial infection from sterile inflammation and the ability to localise even hidden infections are critical for patient management. Hence, highly sensitive imaging strategies that directly target bacteria instead of inflammatory cells are desirable. We follow two approaches to develop bacteria-specific positron emission tomography (PET): targeting the bacterial carbohydrate catabolism and the iron uptake by siderophores. Targeting carbohydrate catabolism, the main issues are late stage radiofluorination directly on the carbohydrate core and therefore to synthesize the corresponding precursors and also important their serum stability against degrading enzymes. We developed a variety of radiofluorinated complex carbohydrates yielding one maltotriose-based fluorine-18-labelled radiotracer as candidate for clinical translation.[1,2] On the basis of the siderophore salmochelin, we also developed a gallium-68-labelled radiotracer showing specific uptake in E. coli in vitro and in vivo.[3] These bacteria-specific radiotracers, which allow sensitive detection and monitoring of bacteria in tissues whole-body, are highly attractive for translation into future clinical diagnostics.