A global crisis in antibiotic resistance threatens human health. We face the specter of rising numbers of bacterial infections untreatable with antibiotics. The overuse of antibiotics in animal agriculture contributes to the problem. Of the global crisis, the National Academy of Sciences' Institute of Medicine recently concluded, "Clearly, a decrease in antimicrobial use in human medicine alone will have little effect on the current situation. Substantial efforts must be made to decrease inappropriate overuse in animals and agriculture as well."