Persisters are not antibiotic-resistant mutants; they are genetically identical to their vulnerable counterparts. Instead they are bacteria that have gone into a dormant state, ceasing the types of cellular activities that antibiotics typically thwart. Previous research has shown that when persisters of other bacterial species are removed from a bath of antibiotics, they begin to grow again. This fact prompted Lewis and his colleagues to try treating B. burgdorferi with antibiotics in pulsed doses—administering the drugs, stopping and then administering them again—to see if they could kill the persisters once they began to regrow. It worked, which suggests that if persisters are responsible for lasting infections in people, treating patients on and off with antibiotics could help. Lewis and his colleagues, as well as the Johns Hopkins scientists, are also exploring other treatment options, such as different drugs and drug combinations.