For many years, physicians and the public assumed that the discovery of new antimicrobial agents would outpace the ability of bacteria to mutate and develop drug resistance. Yet the development of new antibiotics has not kept up with bacterial evolution, especially since the late 1990's. At that time a multitude of pharmaceutical companies abandoned antibiotic research because of strong economic disincentives. For example, it is challenging for these companies to recuperate the investment (typically in the hundreds of millions of dollars) made in developing a new antibiotic, which is...