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Why Scientists Are Trying Viruses To Beat Back Bacteria

Posted: October 18, 2013

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Researchers say naturally occurring viruses that target bacteria might one day help help treat human infections with germs that are resistant to antibiotics. The research is still in the early stages, and there are quite a few challenges to overcome before a treatment can even be tested in humans.

Clostridium difficile, a bacterium that causes severe diarrhea, can be difficult to treat with antibiotics.

Clostridium difficile, a bacterium that causes severe diarrhea, can be difficult to treat with antibiotics. Stefan Hyman

Not all viruses are bad for us. Some of them might even help up us fight off bacterial infections someday.

Naturally occurring viruses called bacteriophages attack specific types of bacteria. So researchers at the University of Leicester decided to try and take advantage of phages' bacteria-destroying powers to treat infections with Clostridium difficile, a germ that that can cause severe diarrhea and inflammation of the gastrointestinal tract.

Over the last six years, microbiologist Martha Clokie has isolated hundreds of phages that can kill various strains of C. difficile. Now her lab has teamed up with the pharmaceutical company AmpliPhi to try and turn phages into a product, perhaps a pill, that could be used in humans.

There's no guarantee the approach will work, and so far it hasn't been put to a rigorous test in humans infected with C. difficile. Still, there are some good reasons to check it out.

C. difficile is difficult to treat with antibiotics and is resistant to many of them. Another problem is that the germ often strikes when people take antibiotics to treat other infections. The antibiotics kill good bacteria along with the bad, weakening the gut's defenses against C. diff.

Doctors are using fecal transplants and synthetic poop as possible solutions. But Clokie says that phages could be a useful alternative. "We're simply harnessing the natural enemy of the bacteria," she tells Shots.

Unlike bacteria, Clokie says, phages are very specific about what they attack—right down to the sub-species. In fact, a single phage wouldn't be able to take on all the strains of C. difficle. So Clokie is working to develop a cocktail of viruses that would be able to kill the most common strains.

While the bacteria can evolve and try to outsmart the viruses, the viruses can do the same, Clokie says. They've been involved in this arms race for thousands of years.

As long as they can come up with the right cocktail, there's a very good chance that this phage therapy could work, according to Tim Lu, an associate professor of bioengineering at MIT. "If you know what you want to kill, it's kind of like a silver bullet targeting that bacteria," he tells Shots.

And delivering the phages to a person's gut shouldn't be a challenge, Lu says.

Phages are already approved for use in meat and poultry production. Manufacturers sometimes spray food with phages that target listeria, a common food-borne bacterium.

But using phage therapy in humans is a bit more complicated. "Phages were discovered before antibiotics came around," Lu says. And they've been used in humans, he says. But the problem is, they have yet to be tested in well-controlled clinical trials.

There's also the question of intellectual property. Phages are naturally occurring, and therefore they're difficult to patent, which could discourage pharmaceutical companies.

Ultimately, Lu says, "The science is real." The stuff does work. But, he says, "It's a change in the way we think about treating infections, I think that's the biggest hurdle in a way."

Copyright 2014 NPR. To see more, visit http://www.npr.org/.

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