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Tainted meats point to superbug C. diff in food

Study finds gut germ in 40 percent of grocery meats; CDC says not to worry


By JoNel Aleccia Health writer msnbc.com

updated 11/18/2008

Image: Meat section in grocery store

An Arizona researcher found 40 percent of meat products tested from three national chain stores were contaminated with bacteria normally associated with severe hospital infections. Federal health officials, however, say more study is needed to determine whether C. diff is transmitted through food.  

A potentially deadly intestinal germ increasingly found in hospitals is also showing up in a more unsavory setting: grocery store meats.

More than 40 percent of packaged meats sampled from three Arizona chain stores tested positive for Clostridium difficile, a gut bug known as C. diff., according to newly complete analysis of 2006 data collected by a University of Arizona scientist.

Nearly 30 percent of the contaminated samples of ground beef, pork and turkey and ready-to-eat meats like summer sausage were identical or closely related to a super-toxic strain of C. diff blamed for growing rates of illness and death in the U.S . — raising the possibility that the bacterial infections may be transmitted through food.

“These data suggest that domestic animals, by way of retail meats, may be a source of C. difficile for human infection,” said J. Glenn Songer, a professor of veterinary science at the Tucson school, who talked with msnbc.com about work now under review by the federal Centers for Disease Control and Prevention.

But specialists from the CDC and scientists who study C. diff said the connection between the presence of C. diff bacteria and infection has not been established and that there’s not enough evidence about food transmission to warrant public alarm.

“There are no documented cases of people getting Clostridium difficile infection from eating food that contains C. difficile,” said Dr. L. Clifford McDonald, chief of prevention and response for a division of the CDC. “However, because C. difficile has been found in some retail meats, that possibility does exist.”

Songer's samples included brands sold in grocery stores across the nation. Contamination ranged from 41 percent of pork products and 44 percent of turkey products to 50 percent of ground beef samples and more than 62 percent of samples of braunschweiger, a type of liverwurst.

Nearly three-quarters of the C. diff spores were toxinotype V, a type linked to illness in pigs and calves and, increasingly, in humans, Songer noted.

80 percent of infections occur in hospitals
C. diff has long been a common, usually benign bug associated with simple, easily treated diarrhea in older patients in hospitals and nursing homes. About 3 percent of healthy adults harbor the bacteria with no problem. But overuse of antibiotics has allowed the germ to develop resistance in recent years, doctors said, creating the toxic new type that stumps traditional treatment.

About 80 percent of C. difficile infections now occur in hospital or health care settings — and the number of infections is rising. About 13 in every 1,000 hospital patients is infected or colonized with the bacteria, a rate between 6.5 and 20 times higher than previously estimated , according to figures released last week by the Association for Professionals in Infection Control and Epidemiology, or APIC. Every day, those infections likely cost $32 million, on average, and claim more than 300 lives, the study showed.

Especially worrisome has been a new, more virulent strain, called NAP1, which produces about 20 times the toxins of ordinary strains. It can cause severe, repeated diarrhea that resists all but the most powerful drugs. In worst cases, C. diff infection can destroy the colon and lead to blood poisoning and death.

It’s not clear, however, where the remaining infections — those that occur outside health settings, in the community — originate. Recent victims have included a 10-year-old girl with no history of antibiotic use who became very ill but recovered and a 31-year-old woman pregnant with twins who spontaneously aborted her babies and then died after becoming infected, according to a 2005 review by the CDC.

“For these community-associated sources, there has to be a source outside the hospitals,” Songer said. “It may well be that retail meats are a source or the main source.”

C. diff is a tricky bug, hard to kill with anything but bleach in the hospital and able to survive most cooking techniques in the kitchen. And, unlike scary infections like E. coli 0157:H7, which has transmitted illness through foods from ground beef to fresh spinach, C. diff can't be traced quickly to its source.

"With difficile, you can eat a nice, thick braunschweiger sandwich today, then two weeks from now you get strep throat, take antibiotics and develop difficile-related disease," Songer explained. "You're weeks separated from the event."

Songer detected C. diff in every type of meat he tested, including uncooked ground beef, pork and turkey; pork sausage and chorizo; and ready-to-eat products including beef summer sausage and pork braunschweiger, a spreadable liver sausage luncheon meat.

He collected 88 samples of retail packaged meats bought from large chain stores near Tucson on three occasions during a two-month period in 2006. Earlier analysis indicated that about 30 percent of samples showed C. diff, but that percentage increased under closer review, Songer said.

Thirty-seven of the samples, or nearly 42 percent, showed evidence of C. diff, including about 40 percent of the cooked products and nearly 48 percent of the ready-to-eat products.

Contamination could be nationwide
All of the samples collected were national brands available in grocery stores across the country, except the pork chorizo, which was locally made. Songer declined to identify the specific brands, saying that it would unfairly target a single producer when the problem is likely endemic to all.

“My perspective on this is not to blow the whistle on the meat production or meat processing agencies but to point out that we may have a problem and if we do we should work together to solve it,” he said.

At least one meat industry official said Songer’s findings served as a warning to producers, but that the research hasn’t been replicated. Liz Wagstrom, assistant vice president of science and technology for the National Pork Board, said she’s awaiting confirmation from the CDC and other sources.

“I feel very confident in the safety of our product,” she said. “If there is any animal-to-human transmission, it is a very small part of the picture.”

James “Bo” Reagan, chairman of the Beef Industry Food Safety Council, declined to discuss specific strategies for addressing C. diff. Instead, in an e-mail to msnbc.com, he said beef producers have spent $27 million on research to identify new food safety technologies and processes.

“Our efforts have resulted in new safeguards throughout the beef production chain and we continue to work with our partners in beef production to find ways to ensure beef is safe,” Reagan wrote in an e-mail. 

‘Yes, it's there’
Songer’s study follows a 2007 report in the CDC journal Emerging Infectious Diseases, which showed Canadian researchers detected C. diff in 12 — or 20 percent — of 60 retail meat samples collected in 2005.

Neither report, however, definitively answers questions about C. diff in the food supply, said the study's lead researcher J. Scott Weese, an associate professor of pathobiology at the University of Guelph in Ontario , Canada .

“Yes, it’s there,” he said. “But we need to find out how much is there.”

Processed meats like those Songer studied may be more likely to show contamination because they combine sources of meat and because they require more handling than, for instance, a pork chop from a single pig, Weese said.

In addition, scientists don’t know when C. diff exposure sparks infection in people — or how much of a dose is necessary to cause infection, said Dr. Dale N. Gerding, a national expert in C. diff epidemiology and a professor with the Stritch School of Medicine at Loyola University in Chicago.

“With a real susceptible source, it only takes a few spores,” he said.

Bug might be in water, soil — even vegetables
But Gerding also noted that C. diff has been found in many places other than hospitals and meat counters, including water sources and soil.
“We actually wouldn’t know if a carrot in the dirt would have it just as much as hamburger,” Gerding said.

That's little comfort to Mary Woodard, 51, of Rock Falls , Ill. , whose 6-year-old granddaughter, Nichole Lilly, contracted a C. diff infection in October. The child hadn't had antibiotics for six months and she'd been nowhere near a hospital or health center. But she wound up doubled over on the floor with severe cramps and diarrhea for nearly two weeks, until a clinic cultured her stool and diagnosed the illness.

Woodard is scared the infection will return, or that it will strike one of her other grandchildren. Word that C. diff has been detected in meat made Woodard think twice, despite CDC assurances to the contrary.

"I'll cut back, probably, on my meat eating," she said. "After seeing her with the bad cramping, I don't want to see her like that again."

Most consumers worried about C. diff infection should pay closest attention to hospitals and health care settings, Gerding said. Lax hand hygiene, improperly cleaned hospital rooms and overuse of antibiotics are far more likely to transmit C. diff than food products.

Although C. diff spores can be hard to kill, even Songer said most healthy consumers don’t need to change their diets because of the bug.

“To bring it right down to personal terms, I haven’t changed my eating habits one bit,” said Songer, who admits he’s a lifelong braunschweiger fan. “I’ve got about 40 pounds in my freezer that I’m eating.”

Further research will clarify the link between C. diff detection in food animals and infection in humans, Gerding said.

“The connection between the animal, the food and the disease has not been made,” he said. “But that doesn’t mean it’s not there.”