Exposure of a bacterial culture to an antibiotic or other lethal stress typically results in the generation of sub-populations of live cells ("persisters") and dead cells, and, in some cases, viable but non-culturable cells. Studies aimed at understanding the mechanisms of antibiotic killing and bacterial persistence will require the purification and analysis of each of these sub-populations in isolation. This paper reports a method based on continuous-flow dielectrophoresis to separate live and dead cells from antibiotic-treated bacterial cultures. Our experiments were carried out on Mycobacterium smegmatis, a model organism that is closely related to the etiological agent of human tuberculosis.