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Staphylococcus aureus: It's What's For Supper

April 26, 2011

If you pay attention to food safety, you'll know that the previous year hasn't been a comforting one. Spinach, lettuce and eggs are just some of the more recent items that have sparked wide-scale food safety scares and illnesses. But the real eyebrow-raiser happened last week.

A new study has indicating that about half of the conventionally farmed meat and poultry sold in the U.S. is widely contaminated with Staphylococcus aureus, a virulent Staph bacteria that can cause serious illnesses and death in humans. The study, conducted by researchers at the Translational Genomics Research Institute (TGen) in Phoenix, Arizona, was published in the April 15 issue of the journal Clinical Infectious Diseases. In addition, about half of the contaminated meat was infected with antibiotic-resistant versions of S. aureus.

Staphylococcus aureus is a familiar and persistent little bugger. It's one of the most prevalent causes of clinical infections globally, but it's not only its inherent nastiness that generates headlines. A new antibiotic-resistant variant of the bacterial strain, ST398, has begun to plague (no pun intended) the meat industry. First discovered in 2003, ST398 is one of the most common causes of community-acquired methicillin-resistant S. aureus, widely known in hospitals and health-care settings as "MRSA" (pronounced

"mersa").

You don't need to have a medical degree to understand that when you render antibiotics ineffective, you're courting trouble. Said the study's authors, "Antibiotics are the most important drugs that we have to treat Staph infections; but when Staph are resistant to three, four, five, or even nine different antibiotics - like we saw in this study - that leaves physicians with few options."

Few options indeed. S. aureus infection can cause a host of unpleasant pathologies ranging from mild skin infections to life-threatening conditions such as pneumonia, sepsis and heart infection.

And if you eat meat, you regularly come in contact with it.

Specifically, the study's authors analyzed 136 samples of 80 brands of beef, chicken, pork and turkey bought from 26 retail stores in five U.S. cities: Chicago; Flagstaff, Arizona; Fort Lauderdale, Florida; Los Angeles; and Washington, D.C. Nearly half - forty-seven percent - of the meat samples were contaminated with S. aureus, and in more than half - 52 percent - of cases, the bacteria found were resistant to at least three classes of antibiotics.

One of the most troubling elements of the study was that meat handling processes weren't necessarily to blame. The researchers used DNA testing to pinpoint the source of the bacterial contamination, and found that it wasn't necessarily improper handling of the meat that was the culprit, but that the animals themselves carried the S. aureus in their bodies before slaughter. Of course, the animals aren't the only places staph infections can come from. About half of humans carry staphylococcus bacteria in their noses and throats, so a sneeze or a cough over raw meat may be enough to contaminate, as well.

But human-to-meat transmission doesn't necessarily explain where the antibiotic-resistant variants of the bacteria are coming from. Researchers believe that the blame for the drug-resistant strain can be laid at the door of excessive antibiotic use in food animals by the meat industry. Last year, the U.S. Food and Drug Administration (FDA) addressed the issue, requesting that the meat industry voluntarily begin limiting the use of antimicrobial drugs in meat production. The agency has recommended that meat farmers use the drugs as judiciously as possible, limiting their use to medical necessity and using them only with the oversight of a veterinarian.

"Developing strategies for reducing (antibiotic) resistance is critically important for protecting both public and animal health," said the FDA in the preamble to its draft guidelines.

There is little evidence thus far that the FDA's "recommendations" have been heeded much, however.

"For the first time, we know how much of our meat and poultry is contaminated with antibiotic-resistant Staph, and it is substantial," said senior study author Lance B. Price, director of TGen's Center for Food Microbiology and Environmental Health. "The fact that drug-resistant S. aureus was so prevalent, and likely came from the food animals themselves, is troubling, and demands attention to how antibiotics are used in food-animal production today," he said.

While the FDA and veterinarians agree that antibiotics are needed occasionally in order to maintain the safety of the U.S. meat supply, critics say the drugs are being used too often and for the wrong reasons. Meat producers routinely use antibiotics on healthy animals to speed up growth and maturity and keep feed costs down. Instead of treating individual animals as needed, farmers are dosing whole herds with antibiotics through feed or water to prevent infection that hasn't yet happened.

The beef industry, for its part, has decried the TGen study and accused its underwriter of having an agenda. "Calling into question the safety of U.S. beef without conclusive scientific evidence is careless and misleads consumers," said the National Cattlemen's Beef Association in a statement. "Pew Charitable Trusts, an agenda-driven organization on this issue, funded this study, which concludes that its extremely small sample size was 'insufficient to accurately estimate prevalence rates' and that 'public health relevance of this finding is unclear.'"

Many other meat industry groups have said their practices are safe and keep food more affordably priced. But concerns nonetheless remain that the routine dosing of meat animals with antibiotics is building so-called "super bugs" that will one day come back to haunt the human race on a large scale.

So what can you do about it, aside from going vegetarian? Obviously, the heat from cooking destroys the bacteria, so be sure that you thoroughly cook any meat you consume. Handling raw meat in the cooking process, however, raises the chances of cross-contamination in the kitchen if proper food handling practices aren't followed. Staphylococcus bacteria can enter the body through cuts and scrapes on the skin, so if you're preparing dinner with a open wound, you could be setting yourself up for trouble. Food safety experts recommend wearing gloves while you handle raw meat, particularly if you have any unhealed wounds on your hands.

More and more consumers, spooked by eating Staph bacteria for supper, are toying with the idea of organic meat. ("Toying" is the right word, particularly if you've ever checked the prices of organic meat.)

Organic meat has a number of benefits over conventional meat. In order to be called "organic," the meat must have been raised and processed using no antibiotics or hormones. The animals' food sources (grain or grass) must have been grown without the use of pesticides or chemical fertilizers (components that can actually wind up in the meat after the animal consumes them) or animal by-products. (Recall that bovine spongiform encephalopathy, or "mad cow disease," resulted from animals being fed ground-up carcasses of other animals that included infected brain and spinal cord tissue). The whole process from animal raising to meat processing cannot contain any genetically modified products, and no preservatives or colors can be added to the meat.

Many people buy organic meat not only for health reasons, but because the organic process is considered more humane to animals. For meat to be called organic, livestock must be given regular access to the outdoors. In many cases, livestock graze naturally on grass, which actually adds health benefits: the meat of grass-fed animals contains more omega-3 and conjugated alpha-linoleic acid, substances that are thought to improve human heart health. Meat from grass-fed animals is also likely to be leaner than meat from grain-fed animals, which means it tends to be higher in protein and lower in cholesterol.

One of the biggest safety benefits with organic meat, however, is its traceability. Organic meat must be easily traceable from the animal's birth to its slaughter and processing to the store which ultimately sells the meat. This means that if there ever were a health risk identified with the meat, both the source and the final destination of the meat could be determined very quickly. (Tracing the source of the infection and the stocks of infected meat in the marketplace has proved to be very difficult in past instances of E. Coli in conventionally produced ground beef, for example.)

But organic meat is out of the question for many Americans' budgets, which puts the onus on the FDA and the USDA to take real leadership to help curb the use of unnecessary antibiotics and hormones in conventionally processed meat. For their part, the TGen researchers have urged a dramatic -- and mandated --  reduction in antibiotic use in food animals.

"There is unequivocal evidence that decreasing antibiotic use in food production decreases antibiotic-resistant bacteria in the animals, decreases antibiotic-resistant bacteria on the foods and decreases antibiotic-resistant bacteria in people," said Dr. Price during a press conference.

But to accomplish the kind of policing that needs to be done to prevent misuse of antibiotics, the FDA and the USDA need bigger guns, said Price.

"They [agencies] need to be monitoring a lot of different kinds of bacteria, they need to be reporting more regularly, and that information needs to be fed back into other parts of the FDA to make recommendations on the antibiotics that are allowed to be used in food animal productions," said Price. "And we need farm-level detailed information about what antibiotics are being used for what purpose and in what quantity."

Given the FDA's recommendations about reducing antibiotic use in meat production last year, it would appear that the agency is slowly coming to agree with scientists and food safety experts. The FDA has acknowledged that, so far, scientific research generally supports the idea that using drugs to enhance animal growth "is not in the interest of protecting and promoting the public health."

The question is whether they're actually going to do anything about it other than issue gentle suggestions that few in the meat industry plan on heeding. If you're as cynical as I am about the issue, it may be time to eat less meat and save your meat dollars for the organic variety, even if it means eating meat only once or twice a week. And steak tartare is probably off the menu.

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