Scientists are turning to predatory bacteria to defeat drug-resistant infections. Microbiologists led by Daniel Kadouri, now at Rutgers University, lately have focused on two such predators—Micavibrio aeruginosavorus, which latches onto a germ and sucks out its innards, and Bdellovibrio bacteriovorus, which burrows into and parasitically reproduces within its prey. Kadouri's group previously showed that both species could kill dangerous microbes, but the predators had not been conclusively tested on drug-resistant strains. Thus, the team decided to unleash each species onto cell cultures of 14 drug-resistant varieties of bacteria commonly found in hospitals, then observed as the hunters wiped out large numbers of the pathogens. The results appeared online May 1 in the journal PLOS ONE.

But would the hunters attack human cells as well? In a study published in PLOS ONE on June 18, Kadouri's team found the microbes could kill bacteria linked with eye infections while leaving human eye cells untouched. “Exploiting nature, tilting the balance in the favor of the host by a means other than antibiotics, is a really important approach,” says Daniel Zurawski, a microbiologist at the Walter Reed Army Institute of Research who studies drug-resistant bacteria.

Every year nearly two million patients acquire infections—often caused by drug-resistant germs—in hospitals in the U.S. alone, according to the Centers for Disease Control and Prevention. Even potent new antibiotics cannot wholly solve this problem, because colonies of virulent germs often encase themselves in biofilms—microscopic layers of protective slime that adhere to almost any surface. Previous work by Kadouri and others has found that predatory bacteria can infiltrate biofilms to kill the microorganisms inside, offering a new method of preventing infection.

Because of the potential sensitivity of an individual's immune system to microbes swimming around the bloodstream, Kadouri thinks the best predatory-bacteria treatment plan “is to apply them onto surface wounds or burns.” He and his colleagues are now trying these therapies on live animals, with an eye toward eventual human trials.