After years of struggling with a persistent, antibiotic-resistant infection in his chest that required regular courses of intravenous antibiotics, you can understand why someone might be open to trying something a little more experimental.

That’s how Benjamin Chan, an associate research scientist in the department of Ecology and Evolutionary Biology at Yale University, landed a patient to test out an experimental form of treatment called phage therapy—and it worked in this single case, according to a case study on the patient published Thursday in Evolution, Medicine, and Public Health.

Bacteriophages are a type of virus that evolved to target specific species of bacteria as their hosts. They're biologically incompatible with any organism other than their bacterial host partner, which means they can't infect humans, they just hunt down the bacteria that can make us sick and destroy them. And because they’re targeted, unlike antibiotics, they’ll only wipe out the bacteria we’re trying to get rid of, and not take out all the good bacteria too.

Though using phages to treat bacterial infections isn’t a new idea—it was common in the early 20th century and was researched f the Soviet Union—antibiotic resistance has drawn new interest to these infection-fighting bugs. Chan has been studying the evolution and genetics of phages. Since there are an estimated 1031 bacteriophages on the planet, there are constantly new species to be discovered, and Chan will take them wherever he can get them.

“There’s another lab upstairs from me that studies fish, I think,” Chan said. “They regularly take samples from lakes and we get the leftovers from their samples to look for new phages.”

One particular phage, originally found in Dodge Pond in Connecticut, was a match for the type of bacteria that had infected the patient’s chest after open heart surgery years earlier. Chan’s research had shown that the phage kills off that bacteria, and also can make it more susceptible to antibiotics.

“It’s a cool trade-off in that if the bacteria evolves to be resistant to the phage it becomes susceptible to antibiotics,” Chan said.

So, with the help of his colleagues in the medical school, he devised a treatment plan that introduced the phages along with an antibiotic to the infected area. The phages quickly went to work. The patient hasn’t had any signs of new infection in more than 18 months.

A single case study is far from conclusive evidence, however. Chan told me for all they know they could have just “gotten lucky,” that the patient recovered. The only way to truly test out phage therapy would be to do larger trials with more people.

Finding patients isn’t hard: Chan said he regularly gets contacted by people interested in trying phage therapy in order to avoid continuous antibiotic treatment. But trials cost money, so it will have to wait until funding comes along. In the meantime, Chan is continuing to study the phages he and others discover so that we’ll know exactly what each one’s superpower is, and how we can use it.