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The Medical Bond: The search is on for a way to image infections

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Going under the knife for surgery is a scary enough prospect by itself. But throw in the risk of contracting a bacterial infection, and even a routine procedure can become a nightmare.

Now, keep in mind that surgical infections only affect fewer than 3 percent of surgery patients nationwide every year and can often be treated effectively. But when infections grow severe, some patients are left fighting for their lives over something that should not have happened in the first place.


To spur a faster recovery for patients in such cases and those with other severe bacterial infections, scientists are figuring out for the first time how to create a picture of where the harmful bugs are in the body.

Doctors can take pictures of broken bones, some tumors, even brain activity. But when it comes to an invasion of bacteria, Anton Bunschoten, Ph.D., says currently approved imaging options are limited to looking for inflammation. Though a body’s local flare-ups can be a result of a bacterial infection, it’s not the sole possible cause — and discerning the source quickly can save lives.

If a patient has a hip replacement, for example, and feels pain and other symptoms after surgery, a minor inflammatory response would require a small intervention, says Bunschoten who’s with the radiology department at Leiden University Medical Center in the Netherlands.

“On the other side, when it’s a bacterial infection, the whole prosthetic has to be removed and a serious antibiotic treatment has to follow,” he explains. “So it’s really important to know if the prosthetic is inflamed due to a bacterial infection or another kind of inflammatory response.”

To take stock of where bacterial imaging research is, Bunschoten’s team looked at the various parallel studies going on and assessed how far along each has come. He reported his findings in the ACS journal Bioconjugate Chemistry.

In his review paper, Bunschoten describes several agents researchers are pursuing for imaging infections: antibiotics, carbohydrates, viruses, enzyme-activated tracers and proteins. He says one set stands out above the rest: antimicrobial peptides, or AMPs. These amino acid chains form a part of the native immune system in all kinds of organisms. They work by sticking to bacteria and busting open their outer walls.

Some researchers are taking advantage of this bacteria-seeking behavior and attaching radioactive and fluorescent labels to AMPs to see if the peptides can be used for imaging. They’ve already had some success with one particular kind, called UBI for short. Researchers have even tested UBIs in patients in bone, soft tissue and for prosthetic and diabetic foot infections and in cases of fever of unknown origin.

Because some of the labels for imaging are radioactive, the risks of exposing patients have to be weighed against benefits. So this type of technique would not be used to confirm a run-of-the-mill ear infection, for example. But for serious infections that occur post-surgery or cause life-threatening diseases like tuberculosis, this kind of imaging could help transform global healthcare.

UBIs are not quite ready for prime time, but because they’ve already been tested in patients, they could be on track for practical use within five years, Bunschoten estimates.

He acknowledges funding from The Netherlands Organisation for Scientific Research.

“Development and Prospects of Dedicated Tracers for the Molecular Imaging of Bacterial Infections”

Click here for the abstract.

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