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Flashy drug spotlights infection

Doctors may be able to watch for invading microbes with a fluorescent antibiotic

GLOWING INFECTION  By fusing a fluorescent chemical to an antibiotic, researchers could visualize bacterial infections in a mouse. Bacteria labeled with the experimental drug appear red; genetically modified bacteria, used as controls, glow blue.

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Glowing antibiotics may dim the chance of severe bacterial infections, according to a study published October 15 in Nature Communications.

Researchers made the experimental drug by fusing a fluorescent tag to vancomycin, an antibiotic that embeds itself in the outer walls of certain disease-causing microbes. The tag allowed scientists to see bacterial invaders in live mice and human cadavers. The method could help doctors thwart serious infections by spying them during early, treatable stages.

“It’s a pretty smart approach,” says biochemist Jianghong Rao of Stanford University who was not involved in the study. Most importantly, he says, vancomycin and the fluorescent tag are already individually approved for human use, so the modified drug should sail through safety tests.

Lead researcher Marleen van Oosten of the University of Groningen in the Netherlands says the method may help doctors monitor infections around surgically implanted materials, such as plates that fix broken bones and stents in arteries.

Bacteria often contaminate such materials during surgery. By the time standard methods detect such infections, it’s often too late to treat. At that point, the patient may have to undergo more surgery to replace the implant, van Oosten says.

She and her colleagues injected mice with a mild dose of the glowing drug and minimal quantities of bacteria. Then, they placed the animals under near-infrared light to see the early infection glow through the skin.  

Surgeons already use near-infrared light with patients and it has fewer health risks than some other imaging techniques, such as X-rays.

To test the method in humans, the researchers implanted plates in the ankles of two cadavers. Before surgery, the team coated the plates with bacteria and with the experimental drug. Using near-infrared light, they could see the drug, embedded in bacteria on the plate, glow through the cadavers’ skin.

Bioengineer Niren Murthy of the University of California, Berkeley says it’s still unclear whether the imaging will work for implants deeper in the body, such as in the hip. But, he says, it’s a good step forward: “Being able to image bacteria with sensitivity in a clinical setting will be very, very useful.”

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