Radiotracers for in situ infection imaging: Experimental considerations for in vitro microbial uptake of gallium-68-labeled siderophores

• Published in: Diagnostic microbiology and infectious disease 2024-12, Vol.110 (4), p.116522, Article 116522
• Main Authors: Akter, Asma, Cooper, Margaret S., Darwesh, Afnan M.F., Hider, Robert C., Blower, Philip J., Price, Nicholas M., Lyons, Oliver, Schelenz, Silke, Mehra, Varun, Abbate, Vincenzo
• Format: Article
• Language: English
• Subjects: 68Ga-siderophores; Deferoxamine - metabolism; Deferoxamine - pharmacology; DFO-B; Diagnostics; Enterobactin - metabolism; Escherichia coli - metabolism; Gallium Radioisotopes; Humans; Infection imaging; PET tracers; Siderophores - metabolism; Uptake method
• ISSN: 0732-8893; 1879-0070; 1879-0070
• DOI: 10.1016/j.diagmicrobio.2024.116522

•Validation of in vitro68Ga-siderophore uptake in E. coli and A. fumigatus.•Uptake results expressed as ‘% Added dose/109 CFU/mL’ to compare bacterial and yeast species.•[68Ga]Ga-DFO-B uptake varies among microbial species.•[68Ga]Ga-DFO-B uptake has no significant effect on assessed bacterial and yeast cell viability. In vitro screening of gallium-68(68Ga)-siderophores in pathogens relevant to infections is valuable for determining species specificity, their effect on cell viability, and potential clinical applications. As the recognition and internalization of siderophores relies on the presence of receptor- and/or siderophore-binding proteins, the level of uptake can vary between species. Here, we report in vitro uptake validation in Escherichia coli with its native siderophore, enterobactin (ENT) ([68Ga]Ga-ENT), considering different experimental factors. Compared with other reporting methods of uptake, ‘% Added dose/109 CFU/mL (% AD/109 CFU/mL),’ considering the total viable count, showed a better comparison among microbial species. Later, in vitro screening with [68Ga]Ga-desferrioxamine B (DFO-B) showed high uptake by Staphylococcus aureus and S. epidermidis; moderate uptake by Pseudomonas aeruginosa; poor uptake by E. coli, Candida albicans, and Aspergillus fumigatus; and no uptake by Enterococcus faecalis and C. glabrata. Except for S. epidermidis, [68Ga]Ga-DFO-B did not reduce the cell viability.