Imaging Diverse Pathogenic Bacteria In Vivo with ¹⁸F-Fluoromannitol PET

Infectious disease remains the main cause of morbidity and mortality throughout the world. Of growing concern is the rising incidence of multidrug-resistant bacteria, derived from various selection pressures. Many of these bacterial infections are hospital-acquired and have prompted the Centers for Disease Control and Prevention in 2019 to reclassify several pathogens as urgent threats, its most perilous assignment. Consequently, there is an urgent need to improve the clinical management of bacterial infection via new methods to specifically identify bacteria and monitor antibiotic efficacy in vivo. In this work, we developed a novel radiopharmaceutical, 2-¹⁸F-fluoro-2-deoxy-mannitol (¹⁸F-fluoromannitol), which we found to specifically accumulate in both gram-positive and gram-negative bacteria but not in mammalian cells in vitro or in vivo. Methods: Clinical isolates of bacteria were serially obtained from wounds of combat service members for all in vitro and in vivo studies. Bacterial infection was quantified in vivo using PET/CT, and infected tissue was excised to confirm radioactivity counts ex vivo. We used these same tissues to confirm the presence of bacteria by extracting and correlating radioactive counts with colony-forming units of bacteria. Results: ¹⁸F-fluoromannitol was able to differentiate sterile inflammation from Staphylococcus aureus and Escherichia coli infections in vivo in a murine myositis model using PET imaging. Our study was extended to a laceration wound model infected with Acinetobacter baumannii, an important pathogen in the nosocomial and battlefield setting. ¹⁸F-fluoromannitol PET rapidly and specifically detected infections caused by A. baumannii and several other important pathogens (Enterococcus faecium, S. aureus, Klebsiella pneumoniae, A. baumannii, Pseudomonas aeruginosa, and Enterobacter spp.). Importantly, ¹⁸F-fluoromannitol PET was able to monitor the therapeutic efficacy of vancomycin against S. aureus in vivo. Conclusion: The ease of production of ¹⁸F-fluoromannitol is anticipated to facilitate wide radiopharmaceutical dissemination. Furthermore, the broad sensitivity of ¹⁸F-fluoromannitol for bacterial infection in vivo suggests that it is an ideal imaging agent for clinical translation to detect and monitor infections and warrants further studies in the clinical setting.