The worldwide spread of resistance to antibiotics among Gram-negative bacteria, particularly members of the ESKAPE group of pathogens, has resulted in a crisis in the treatment of hospital acquired infections. In particular, the recent dissemination of a serine carbapenemase (e.g., KPC) in Enterobacteriaceae in US hospitals now poses a considerable threat to the carbapenems and other members of the beta-lactam class of antimicrobial agents.