For years, scientists and science writers have been sounding loud alarmsabout drug-resistant bacteria that can shrug off our most potent antibiotics. They are hard to kill, and so kill us with greater ease. These superbugs are undeniably worrying but they’re only part of the problem—it is entirely possible for bacteria to defy antibiotics without actually resisting them.

All of our antibiotics are designed to kill fast-growing microbes. Bacteria can weather these assaults by entering a dormant state, and waiting until the drugs have worn off. These sleeper cells are called persisters. They’re the reason why bacteria sometimes cause long-lasting infections that repeatedly bounce back despite our best attempts to treat them. Each wave of drugs wipes out most of the microbes, but a small group of persisters can survive to re-start a new wave of infection.

Persisters are not drug-resistant; if you whacked them with antibiotics while they were growing, they’d die. But give the same drugs to a patient, and not much happens. The bacteria survive because of their dormant nature, because of how they behave rather than what they are.

We’ve known about persisters since the 1940s, but they are hard to study and to kill. Many scientists are tackling the issue of drug resistance but persistence has, ironically enough, lain largely dormant.

But Kim Lewis from Northeastern University has now found an exciting way of killing persisters, with an antibiotic called ADEP4 that forces these cells to eat themselves in their sleep. He hasn’t tested it in humans yet, but it can completely clear severe and long-lasting infections in mice. It even kills persisters that are also resistant to traditional antibiotics, such as MRSA. It’s a very important milestone,” says Lewis.