Antibiotic resistance is one of the world’s most urgent public health threats. In the United States alone, tens of thousands of deaths result each year from drug-resistant strains of common bacteria such as Staphylococcus aureus and Enterococcus faecium, which can cause virtually untreatable hospital-acquired infections. Perilously few new classes of antibiotics are being developed to fight infections that have become resistant to traditional treatments, and bringing any new drugs to market could take decades.