Imaging Enterobacteriaceae infection in vivo with ¹⁸ F-fluorodeoxysorbitol positron emission tomography

Abstract

The Enterobacteriaceae are a family of rod-shaped Gram-negative bacteria that normally inhabit the gastrointestinal tract and are the most common cause of Gram-negative bacterial infections in humans. In addition to causing serious multidrug-resistant, hospital-acquired infections, a number of Enterobacteriaceae species are also recognized as biothreat pathogens. As a consequence, new tools are urgently needed to specifically identify and localize infections due to Enterobacteriaceae and to monitor antimicrobial efficacy. In this report, we used commercially available 2-[18F]-fluorodeoxyglucose (18F-FDG) to produce 2-[18F]-fluorodeoxysorbitol (18F-FDS), a radioactive probe for Enterobacteriaceae, in 30 min. 18F-FDS selectively accumulated in Enterobacteriaceae, but not in Gram-positive bacteria or healthy mammalian or cancer cells in vitro. In a murine myositis model, 18F-FDS positron emission tomography (PET) rapidly differentiated true infection from sterile inflammation with a limit of detection of 6.2 ± 0.2 log10 colony-forming units (CFU) for Escherichia coli. Our findings were extended to models of mixed Gram-positive and Gram-negative thigh co-infections, brain infection, Klebsiella pneumonia, and mice undergoing immunosuppressive chemotherapy. This technique rapidly and specifically localized infections due to Enterobacteriaceae, providing a three-dimensional holistic view within the animal. Last, 18F-FDS PET monitored the efficacy of antimicrobial treatment, demonstrating a PET signal proportionate to the bacterial burden. Therapeutic failures associated with multidrug-resistant, extended-spectrum β-lactamase (ESBL)–producing E. coli infections were detected in real time. Together, these data show that 18F-FDS is a candidate imaging probe for translation to human clinical cases of known or suspected infections owing to Enterobacteriaceae.

Validation of 2-18F-Fluorodeoxysorbitol as a Potential Radiopharmaceutical for Imaging Bacterial Infection in the Lung

“…This finding confirms that 18 F-FDS can be used to specifically differentiate bacterial infection from sterile inflammation, an ability that is extremely critical for early and effective treatment in the clinic. Our findings are consistent with those of a published study (12) that also used 18 F-FDS to image lung infection caused by K. pneumoniae, but the strain of bacteria used in that study was the ATCC 700721 strain, better known as MGH 78578, which is relatively avirulent and has a 50% lethal dose of 10 8 CFUs (23). In contrast, we used a highly virulent strain (50% lethal dose, 100 CFUs) called ATCC 43816 (13).…”

“…There is still a shortage of effective bacterial infection-specific imaging approaches such as antibodies, antimicrobial peptides, and antibiotics and small molecules (e.g., zinc(II)-dipicolylamine derivatives and the thymidine kinase substrate 1-(2-deoxy-2-fluoro-b-D-arabinofuranosyl)-5-iodoracil) (17)(18)(19)(20)). 18 F-FDS has been shown not only to differentiate bacterial infection from sterile inflammation but also to discriminate gram-negative bacteria from gram-positive pathogens, cancer cells, and mammalian cells (12). Moreover, a recent study on healthy volunteers using 18 F-FDS did not detect adverse effects, holding potential for clinical application (21).…”

“…A recent study indicated that 18 F-FDS specifically accumulates in several strains of gram-negative bacteria but not gram-positive bacteria, with 1,000-fold higher uptake in Escherichia coli than in mammalian cells. PET/CT imaging results showed that 18 F-FDS accumulated in the thigh of a mouse infected with live E. coli but not in one treated with dead E. coli, whereas there was no significant difference in 18 F-FDG uptake between the two thighs, indicating the high selectivity of 18 F-FDS (12). Thus 18 F-FDS is a promising PET radiotracer for imaging bacterial infection.…”

“…The K. pneumoniae strain (ATCC 43816) was kindly provided by Virginia Miller, of the University of North Carolina at Chapel Hill. 18 F-FDS was prepared from commercially available 18 F-FDG using a published method (12). Briefly, 18 F-FDG was mixed with 5 mg of solid sodium borohydride at 35°C for 15 min and then quenched with acetic acid, after which the pH was adjusted to 7.4 with sodium bicarbonate.…”

Bacterial infection imaging with [ 18 F]fluoropropyl-trimethoprim

“…Given these clear potential uses, past efforts have focused largely on nuclear techniques based on radiotracers derived from peptides, antibiotics, and sugars due to the required sensitivity needed for identifying bacteria (3,4). Still, no bacterial imaging agent is routinely used clinically, and among the previously developed agents many are not sufficiently broad spectrum to provide strong negative and positive predictive values to inform clinical decision making.…”