Innovative PET tracer identifies, tracks bacterial lung infection

A team of researchers has proven a new radiotracer, 2-18F-fluorodeoxysorbitol (18F-FDS), more adept at tracking bacterial infection in lungs than current imaging methods, while also distinguishing bacterial infection from inflammation.

The team, led by Junling Li, PhD, with the Department of Radiology, University of Louisville School of Medicine in Kentucky, published the study online Jan. 8 in The Journal of Nuclear Medicine.

"Currently, bacterial infections can be diagnosed only after they have become systemic or have caused significant anatomical tissue damage, a stage at which they are challenging to treat owing to the high bacterial burden," said fellow author Chin K. Ng, PhD, in a release from the Society of Nuclear Medicine and Molecular Imaging.

And according to the study, approximately two million patients develop a hospital-acquired infection each year, making bacterial infections a major contributor of morbidity and mortality, despite the presence of antibiotics.

“18F-FDG cannot distinguish infections from other conditions such as cancer and inflammation, making it nonspecific for bacterial imaging,” Ng et al. wrote in the study. “Therefore, there is a need for rapid whole-body imaging techniques that can localize a pathogen with specificity and provide a quantitative readout of disease-burden response to treatment.”

Researchers inoculated mice with either live Klebsiella pneumoniae bacteria to bring about lung infection, or the dead strain of the bacteria to produce inflammation. From there, half of the mice that were given live bacteria underwent PET/CT using either 18F-FDS or 18F-FDG on days zero, one, two and three to monitor the progression of the disease post-infection.

The other half underwent bioluminescent imaging, with follow-up PET/CT scans administered using 18F-FDS in mice with visible infection. In the group of mice with inflammation, half were imaged with PET/CT using 18F-FDS and half with 18F-FDG from Day 1 to Day 4.

Both the PET tracers—18F-FDS or 18F-FDG—were effective in determining the degree of bacterial infection, but only 18F-FDS had the ability to differentiate lung infection from inflammation.

“18F-FDS whole-body PET/CT imaging in mice has shown to be a unique imaging technique that could differentiate infection from inflammation. This same technique could potentially be used in patients to identify infection sites and determine the bacterial infection class, so that patients could avoid taking antibiotics that are known to have no effect against specific bacteria,” Ng noted in the release.

“This and other new PET imaging agents demonstrate that molecular imaging and nuclear medicine can offer unique technologies for patient care and will continue to play a key influential role in healthcare,” he also stated.