If you’ve ever gone to the doctor with a throbbing sinus infection and come home with a prescription for antibiotics, you know why these drugs are considered the crown jewels of modern medicine. But, as is often the case, too much of a good thing can be disastrous.

Antibiotics are routinely given in feed and water to perfectly healthy chickens, pigs, and cattle on conventional industrial farms, mostly to promote faster growth and to compensate for crowded and unsanitary conditions. Antibiotics’ rampant use—both on farms and in human health care—has led to the emergence of “superbugs,” or antibiotic-resistant bacteria.

In the last decade, the number of cases of MRSA (a particularly virulent and multidrug-resistant staph bacteria) in children has jumped tenfold, according to a study recently published in Pediatrics. A new strain of MRSA has been linked directly back to farm animals, says Maryn McKenna, author of Superbug (Simon & Schuster, 2010). “Only a few people so far have been made sick by this new strain, but it’s a warning bell,” she says. “We could be at the bottom of a rapidly climbing epidemic curve.”

In 2008, scientists at Louisiana State University tested 120 samples of meat bought at local grocery stores and found that 5 percent contained MRSA. And the Centers for Disease Control and Prevention found other drug-resistant bacteria such as salmonella, E. coli, and campylobacter in 80 percent of the meat samples it tested.

The issue is gaining a sense of urgency; last year for the first time, FDA officials acknowledged that excessive use of antibiotics on farm animals should be curtailed, although the agency has yet to take any official steps.

By the numbers
70 Percent of antibiotics administered in the United States that are used on healthy livestock
19,000 Americans killed each year by the superbug MRSA
7 million Americans sent to the doctor or ER by MRSA annually
$ 8 billion Minimum medical costs linked to MRSA annually
$ 200 million Minimum annual cost to meat industry to eliminate antibiotic use on healthy animals
Sources: Union of Concerned Scientists; U.S. General Accounting Office; R. Monina Klevens, DDS, MPH, Centers for Disease Control and Prevention