It sounds futuristic, but it's actually a very old technique for fighting bacterial infections, and many researchers now believe it will be an indispensable tool in the fight against antibiotic resistance.

Meet bacteriophages: viruses 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 making us sick and destroy them.

Phages were discovered in 1917. In the early 20th century, phage therapy was used to treat all kinds of bacterial infections, according to Daniel Nelson, an assistant professor at the University of Maryland who studies bacteriophages. But after penicillin was discovered, that changed.

"Everything went to antibiotics and phage therapy research stopped in western countries," said Nelson.