Cattle graze in a field near Sacramento, Calif. California Gov. Jerry Brown, along with many health advocacy groups, has called the overuse of antibiotics "an urgent public health problem."
Patients receive treatment at the Chest Disease Hospital in Srinagar, India. The country has one of the highest rates of drug-resistant tuberculosis in the world, in part because antibiotics for the disease are poorly regulated by the government.
Tyson Foods says it has already reduced its use of human-use antibiotics by 80 percent over the past four years. Here, Tyson frozen chicken on display at Piazza's market in Palo Alto, Calif., in 2010.
An employee of the drug company Apotex, examines some Ciprofloxacin at the plant in Canada. Cipro is commonly given to travelers for diarrhea. More than 20 million Cipro doses are prescribed each year in the U.S.
David Livermore, the director of the Antibiotic Resistance Monitoring and Reference Laboratory in London, studies a new class of superbugs, called carbapenem-resistant Enterobacteriaceae, or CRE.
Suzanne Plunkett/Reuters /Landov