Why there are pathogens such as MRSA in our pork

We don't add antibiotics to baby food and Cocoa Puffs so that children get fewer ear infections. That's because we understand that the overuse of antibiotics is already creating "superbugs" resistant to medication.

Yet we continue to allow agribusiness companies to add antibiotics to animal feed so that piglets stay healthy and don't get ear infections. Seventy percent of all antibiotics in the United States go to healthy livestock, according to a careful study by the Union of Concerned Scientists — and that's one reason we're seeing the rise of pathogens that defy antibiotics.

These dangerous pathogens are now even in our food supply. Five out of 90 samples of retail pork in Louisiana tested positive for MRSA — an antibiotic-resistant staph infection — according to a peer-reviewed study published in Applied and Environmental Microbiology last year.

Regardless of whether the bacteria came from the pigs or from humans who handled the meat, the results should sound an alarm bell, for MRSA already kills more than 18,000 Americans annually, more than AIDS does.

MRSA (pronounced "mersa") stands for methicillin-resistant Staphylococcus aureus. People often get it from hospitals, but a new strain called ST398 is emerging and seems to find a reservoir in modern hog farms. Research by Peter Davies of the University of Minnesota suggests that 25 percent to 39 percent of American hogs carry MRSA.

Public health experts worry that pigs could pass on the infection by direct contact with their handlers, through their wastes leaking into , or through their meat, though there has been no proven case of someone getting it from eating pork. Thorough cooking will kill the bacteria, but people often use the same knife to cut raw meat and then to chop vegetables. Or they plop a pork chop on a plate, cook it and then contaminate it by putting it back on the original plate.

Yet the central problem here isn't pigs, it's humans. Unlike Europe and South Korea, the United States still bows to agribusiness interests by permitting the nontherapeutic use of antibiotics in animal feed. That's unconscionable.

The peer-reviewed Medical Clinics of North America concluded last year that antibiotics in livestock feed were "a major component" in the rise in antibiotic resistance.

"We don't give antibiotics to healthy humans," said Robert Martin, who led a Pew Commission on industrial farming that examined antibiotic use. "So why give them to healthy animals just so we can keep them in crowded and unsanitary conditions?"

The answer is simple: politics.

Legislation to ban the nontherapeutic use of antibiotics in agriculture has always been blocked by agribusiness interests. Louise Slaughter of New York, who is the sole microbiologist in the House of Representatives, said she planned to reintroduce the legislation this coming week.

"We're losing the ability to treat humans," she said. "We have misused one of the best scientific products we've had."

That's an almost universal view in the public-health world. The Infectious Diseases Society of America has declared antibiotic resistance a "public health crisis" and recounts the story of Rebecca Lohsen, a 17-year-old New Jersey girl who died from MRSA in 2006. She came down with what she thought was a sore throat, endured months in the hospital, and finally died because the microbes were stronger than the drugs.

This will be an important test for President Barack Obama and his agriculture secretary, Tom Vilsack. Traditionally, the Agriculture Department has functioned mostly as a protector of agribusiness interests, but Obama and Vilsack have both said all the right things about looking after eaters as well as producers.

So, Mr. Obama and Mr. Vilsack, will you line up to curb the use of antibiotics in raising American livestock? That is evidence of an industrial farming system that is broken: For the sake of faster-growing hogs, we're empowering microbes that endanger our food supply and threaten our lives.

Nicholas D. Kristof is a regular columnist for The New York Times.