Repeated exposure to antibiotics can lead germs to become resistant to the drugs, so that they are no longer effective. The Centers for Disease Control and Prevention estimates that drug-resistant bacteria cause 23,000 deaths and 2 million illnesses each year in the United States.

The World Health Organization said last year that bacteria resistant to antibiotics have spread to every part of the world and might lead to a future where minor infections could kill. Antibiotic resistance also threatens animal health, agriculture, and the economy.

In an interview with WebMD, President Barack Obama said over-prescribing antibiotics is a serious problem.