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Potentially fatal bacteria found in pigs, farmworkers

Federal agencies urged to check for MRSA in meat

Last updated June 8, 2008 9:46 p.m. PT

By ANDREW SCHNEIDER
P-I SENIOR CORRESPONDENT

Federal food safety and public health agencies are being urged to begin checking meat sold across the country for the presence of MRSA, a potentially fatal bacteria. Scientists have found the infection in U.S. pigs and farmworkers.

Members of Congress and public health advocates are demanding that the government determine whether highly infectious MRSA has entered the food supply.

MRSA -- methicillin-resistant Staphylococcus aureus -- can be extremely dangerous, according to the federal Centers for Disease Control and Prevention. Dr. Monina Klevens examined the cases of the disease reported in hospitals, schools and prisons in one year and extrapolated that "94,360 invasive MRSA infections occurred in the United States in 2005; these infections were associated with death in 18,650 cases."

The infection has been reported among livestock and farmworkers in Europe, Scandinavia and Canada, but the U.S. government has yet to test animals in this country.

Last week, the Seattle P-I's "Secret Ingredients" blog disclosed that Tara Smith, an assistant professor at the University of Iowa Department of Epidemiology, and her graduate researchers found MRSA in more than 70 percent of the pigs they tested on farms in Iowa and Illinois.

In what is apparently the first testing of swine for MRSA in the U.S., Smith and her team swabbed the noses of 209 pigs on 10 farms. They also found the bacteria among livestock workers employed by those hog operations.

On Friday, at the annual meeting of the American Society for Microbiology in Boston, Abby Harper, one of Smith's graduate assistants, presented the results of the study on farmworkers. She said she and Michael Male tested 20 workers at the Iowa swine farms and found that 45 percent carried the same MRSA bacteria as the pigs.

Smith said she is working with collaborators in Minnesota, Ohio, North Carolina and other areas to examine more swine farms. "We're going to be looking at conventional, free-range and organic or antibiotic-free pigs," she said.

"We will be paying special attention to the antibiotics that are being used, because there are indications that the tetracycline used in swine farming may be the cause of the spread of MRSA," she explained.

A link between increased use of antibiotics and an increased incidence of MRSA is being hotly debated.

Long before MRSA was identified as a potential killer in the early 1960s, public health professionals anguished over the excessive use of antibiotics because they believed it caused bacteria to become resistant to the very medications used to control them.

From the 1960s to the 1980s, MRSA was considered mainly as a threat to hospital and nursing home patients and those who cared for them.

But in the mid-1990s, the CDC reported that the drug-resistant bacteria had broken out of the institutional medical setting and outbreaks were being found among the young and healthy. A virulent strain called CA-MRSA was being reported at schools and was being found in some military units and among high school, college and professional athletes.

During the same period, prophylactic use of antibiotics to prevent disease among livestock went from rare to commonplace. Today, the food fed to fish, fowl, cows, pigs and sheep raised for human consumption is laced with antibiotics.

The similarity between the timeline for increased use of antibiotics in livestock and the soaring rate of MRSA in the general population has already caught the attention of academic researchers and is likely to spark demands for additional research funds.

Earlier this year, Dr. Scott Weese of the Department of Pathobiology at the Ontario Veterinary College told those attending the International Conference on Emerging Infectious Diseases at the CDC that he and his colleagues had found MRSA in 10 percent of 212 samples of pork chops and ground pork bought in four Canadian provinces.

"I think it is very likely that the situation is the same in the U.S.," he told the P-I. "We've proven MRSA is in pigs and the marketed pork in Canada, and we know that it's also in U.S. pigs. It's inconceivable that it wouldn't also be found in the pork products from those pigs."

Dr. Rebecca Goldburg, senior scientist with the Environmental Defense Fund, said, "There are now more deaths in the USA from MRSA than from HIV-AIDS, but U.S. officials appear in denial about animal agriculture as a source of these deadly bacteria."

Goldburg said that the identical strain of MRSA that the researchers in the Midwest and Canada identified in pigs has been linked "with serious human illness including skin, wound, breast, and heart infections, as well as pneumonia."

Last week, according to British newspapers, scientists reported that three patients in separate hospitals in Scotland were infected with the ST398 strain of MRSA, the same strain that Smith and her researchers found in Midwest farms.

What makes this particularly important, public health experts told the P-I, is that doctors reported that none of the patients worked on a farm or had a close association with farm animals, raising the possibility that the so-called superbug has entered the food chain in Britain.

So who is checking to see if antibiotic-resistant staph bacteria are in the 762 million pounds of Canadian pork that's imported into the U.S. each year and in the millions more pounds produced here?

Apparently no one.

That duty should belong to the U.S. Department of Agriculture for imported meat, and the Food and Drug Administration for meat sold domestically.

Dr. David Goldman is in charge of the USDA's four laboratories that examine imported food.

"Any pathogen or hazard that's transmitted through the foods we regulate is a potential issue for us, and so you know, certainly we are aware of the study (Weese) did," Goldman said during an interview at a recent food-safety meeting in Seattle.

"There is no indication MRSA has been identified in swine going into the retail market. Not in this country. Not in swine or other livestock being sold for food in this country," the doctor added.

But none of the USDA labs that he runs is checking for MRSA in imported meat.

"We just don't have a test for it," Goldman said.

The FDA is aware of Weese's study, but "we do not yet have similar data with regards to the MRSA situation among food animals and retail meats," said Mike Herndon, an agency spokesman.

Responding to questions before Smith's study was released, Herndon said there was one MRSA strain of "particular concern in the veterinary medicine and food safety arenas." That was the strain that Smith found in the Midwest swine and their farmers.

Nevertheless, the FDA and USDA eagerly pointed to a group called the National Antimicrobial Resistance Monitoring System as the protector of humans from bacteria in food.

The coalition of scientists from several federal agencies primarily target salmonella, campylobacter and E. coli.

However, according to USDA's Goldman, the group does not screen for MRSA.

The National Pork Producers Council said there is no cause for concern.

"There is nothing to worry about; MRSA (in pigs) has not been found this side of the border," a spokeswoman said. "USDA and CDC have given our pigs a clean bill of health."

A CDC spokeswoman said that she could find "no indication we made that statement."

According to congressional investigators, the pork lobbyists have said their industry would oppose any attempt to test all livestock for MRSA, calling the testing "unnecessary to protect public health."

Some members of Congress are insisting that the government do more to determine MRSA's threat to the food supply.

Rep. Henry Waxman, D-Calif., chairman of the House Committee on Oversight and Government Reform, warned last week that there is "overwhelming evidence" that the overuse of antibiotics in industrial livestock production is endangering the effectiveness of many of the most crucial antibiotics for humans.

"Americans have experienced firsthand the importance of ensuring that we preserve our arsenal (of antibiotics) to fight the new and emerging superbugs, like MRSA," Waxman said at a health hearing on FDA and animal drug issues.

"We know that the overuse of antibiotics hampers our ability to do that."

The issue was addressed in a report on industrial farm animal production by The Pew Charitable Trusts and Johns Hopkins' Bloomberg School of Public Health.

The recently issued report recommended: "Improve monitoring and surveillance of antimicrobial resistance in the food supply, the environment, and animal and human populations in order to refine knowledge of antimicrobial resistance and its impacts on human health."

Meanwhile, some infection-control experts say that proper cooking will kill the MRSA bacterium.

The health threat for butchers and cooks alike, if there is one, will come from improperly handled meat.

"If people wash their hands after handling raw pork and prevent cross-contamination, risks should be very low," Weese said from Canada.

"The main possible concern is that people could get MRSA on their hands from raw pork, then touch their nose. The nose is the prime site for MRSA to live," he said.

Some public-heath experts worry that butchers and professional and home cooks may be infected if MRSA bacteria on their hands entered a cut or a wound.

In a cautionary note, Weese warned that MRSA could also be in beef, chicken and lamb. But no one, he said, is checking.

P-I senior correspondent Andrew Schneider can be reached at 206-448-8218 or andrewschneider@seattlepi.com. Read his Secret Ingredients blog at blog.seattlepi.com/secretingredients.

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