Antibiotic resistance is a growing problem across the world. More than 70 percent of antibiotics important to human medicine in the U.S. are sold for livestock use, according to the Food and Drug Administration. And the Centers for Disease Control and Prevention and the World Health Organization have said the overuse of antibiotics has led to a global health crisis because the more people are exposed to them, the less effective they are. Every year in the U.S., at least 2 million people become infected and 23,000 people die after becoming infected with drug-resistant bacteria, according to the CDC.