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New label will allow physicians to pinpoint location of bacterial infections

Doctors desperately need new tools to combat bacterial infections —  battling bacteria that have developed resistance to existing antibiotics is particularly problematic. Part of the challenge with severe infections is identifying the location of the bacteria to target them precisely and to monitor how a treatment is working.

Now, a team of researchers, led by Sanjiv "Sam" Gambhir, MD, PhD, has developed a new labeling molecule, called 6"-18F-fluoromaltriose, that makes bacterial infections visible in PET scans. Unlike some other labels, or tracers, the molecule identifies all bacteria, including Pseudomonas aeruginosa, a type shown at right that is involved in some drug-resistant biofilms that develop in hospital-based infections. Gambhir directs the Canary Center for Cancer Early Detection at Stanford and is the chair of radiology.

The research appears in The Journal of Nuclear Medicine.

The new tracer targets a molecule found in the cell walls of all bacteria called a maltodextrin (a type of sugar) transporter. Importantly, maltodextrin transporters are not found in human cells, so the tracer can precisely label bacteria only, rather than the body's inflammatory reaction to an infection. One caveat is that the tracer doesn't work for bacteria that are hidden inside human cells, Gambhir pointed out in an email.

Also, the tracer does not identify the type of bacteria -- a secondary test is needed for that, Gambhir said. The research team anticipates that the tracer will be most helpful for problematic infections in hospitalized patients, where precisely tracking the infection is important.

Traditionally, bacterial infections are diagnosed using a biopsy and then culturing the sample, but these techniques only hunt for infection in a particular spot. A PET tracer can identify infection throughout the body, Gambhir added.

Gambhir said he anticipates the tracer will be available for human use in 2018, pending its approval by the U.S. Food and Drug Administration. Gambhir explains:

The hope is that it will become a clinical tracer useful for detecting where bacterial infections are in the body and just as importantly tracking response to therapy to make sure that bacteria are being destroyed early in the treatment course.

Previously: New study shines light on how to better engineer fluorescent proteins, Award-winning project takes on threat of multidrug-resistant bacteria and A dye to try: New compound provides improved imaging, safety
Image by U.S. Centers for Disease Control and Prevention - Medical Illustrator 

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