Pork Chops with a side of antibiotic-resistant staph please

photo by Getty Images

There is an unfortunate statistic out there that your average eater just isn't aware of.  Roughly 84% of our meat hogs, 83% of our feedlot-raised beef, and 60% of our broiler chickens (down from 89% in 1995) that we consume in this country receives regular doses of antibiotics.  In fact, over 70% of all the antibiotics administered in the US go to our meat animals and only 30% go for human treatment. Of that 70% given to livestock and poultry, 90% are dosages known as "non-therapeutic" meaning they are not administered due to a specific illness or disease in the animal, they are administered defensively to prevent illness or disease, and to improve growth.  Many of these antibiotics are the same ones given to your children, your mom, or yourself when you get sick, things like fluoroquinolones, cefquinones, oxacillin, penicillin, amoxicillin, tetracycline, erythromycins, and bacitracin.  However, we never administer antibiotics in humans as a preventative tool nor do we give it in low, non-lethal (to the bacteria) doses. Remember what the doctor always says when she writes that prescription?  Use the entire dose, even if the symptoms go away.  That way you will ensure the death to of all of the bacteria instead of allowing a few to survive and develop resistance to the drug.  So while in humans we don't use antibiotics prophylactically nor do we use non-therapeutic dosages why is this practice allowed in animal agriculture?  What are the consequences?

From the Keep Antibiotics Working, a coalition of health-care professionals, consumer advocates, environmentalists, scientists, and humane animal treatment groups, this is how antibiotic resistance happens and how these bacteria can be transmitted to humans (as is the case with MRSA- Methicillin-Resistant Staphylococcus aureus, more on that below):

When bacteria are initially exposed to an antibiotic, those most susceptible to an antibiotic will die quickly, leaving the hardier surviving bacteria to pass on the characteristics or genes that make them resistant. Bacteria are extremely numerous, and remarkably prolific. Under optimal conditions, a single bacterium can produce a billion offspring in a single day. Even if no bacteria initially have the ability to survive exposure to an antibiotic, random mutation of bacterial DNA generates a wide variety of genetic changes, some of which - sooner or later - will confer resistance.

Many bacteria can live in both humans and animals; many live in the environment as well. Some are pathogens (cause disease) in both humans and animals, and some in one but not the other. Either animals or the environment, therefore, may serve as "reservoirs" for bacteria capable of causing disease in humans. Of course, animals or the environment can act as reservoirs for non-pathogenic bacteria as well. These bacteria pose a less direct, though still significant risk to humans since they may carry and transfer to disease-causing bacteria, the genes that will make them resistant to one or more antibiotics.

Different routes by which antibiotic-resistant bacteria can move from animals to humans can be summarized as food, environment and the workplace:

One example of a growing bacterial problem for humans that has ties to livestock and increasing antibiotic resistance is a particularly nasty strain of staphylococcus.  Methicillin-Resistant Staphylococcus aureas, MRSA, is a type of staph that is resistant to a common class of antibiotics- the beta-lactams.  Just what is MRSA and why should we be concerned about it?  Also from the folks at Keep Antibiotics Working:

Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria that is resistant to certain antibiotics. These antibiotics include methicillin and other more common antibiotics such as oxacillin, penicillin and amoxicillin. MRSA infections are usually skin infections, such as abscesses, boils, and other pus-filled lesions. In older adults and people who are ill or have weakened immune systems, ordinary staph infections can cause serious illness.

A study published in October of 2007 in the Journal of the American Medical Association (JAMA) (Klevens et al. 2007) estimated there were almost 100,000 U.S. cases of invasive methicillin-resistant Staphylococcus aureus (MRSA) infections in 2005 leading to nearly 19,000 deaths. In comparison, HIV/AIDS killed 17,000 people that year. These unexpectedly high numbers combined with a number of school outbreaks have propelled MRSA into the news and made many people aware that it is a serious public health problem.

What many people do not know is that MRSA has also been traced to animals raised for food production, especially pigs. These animals are often fed antibiotics at low doses for disease prevention and growth promotion, creating perfect conditions for antibiotic resistance to flourish. One Dutch study from 2007 found that 11% of pigs from 31 farms were positive for MRSA with antimicrobial medication of pigs a risk factor (van Duijkeren et al. 2007).

A study published in Veterinary Microbiology in October of 2007 has found MRSA prevalent in Canadian pig farms and pig farmers, pointing to animal agriculture as a source of the deadly bacteria. The Veterinary Microbiology study (Khanna et al. 2007) is the first to show that North American pig farms and farmers commonly carry MRSA. The study looked for MRSA in 285 pigs in 20 Ontario farms. It found MRSA at 45% of farms (9/20) and in nearly one in four pigs (71/285). One in five pig farmers studied (5/25) also were found to carry MRSA, a much higher rate than in the general North American population. Two different types of MRSA were detected in the Canadian pigs. One strain ST398 has been found mainly in pigs and in people that work with them. The other strain USA100 was one of the most common causes of MRSA infections in people in the U.S. and Canada. Both types of MRSA have caused serious infections in people.

In early 2008, Tara Smith, an epidemiology researcher at the University of Iowa, and her graduate assistants were the first to test pigs for MRSA in the U.S. They swabbed the noses of 209 pigs from 10 farms in Iowa and Illinois and found MRSA in 70 percent of the pigs (read the abstract from a presentation at the 2008 ICEID conference). At the June 2008 meeting of the American Society for Microbiology, one of Smith's graduate assistants presented the results of another study that they did on 20 workers at the Iowa pig farms. They found that 45 percent of the workers carried the same type of MRSA bacterium as the pigs. As a recent Seattle Post Intelligencer article makes clear, neither meats nor live animals are being systematically tested for MRSA in the United States--a dangerous situation that KAW plans to address.

Until recently, conventional wisdom had MRSA pegged as an opportunistic infection occurring mainly in hospitals. The JAMA study referenced above found that even healthy people are developing MRSA infections. The Veterinary Microbiology studies and Smith's preliminary results in the U.S. point to pig farms as a community source of MRSA, demonstrating the need for the United States government to start systematic testing of its livestock for MRSA as well as determining if livestock strains of MRSA are present in U.S. hospitals.

Keep Antibiotics Working believes that identifying and controlling community sources of MRSA is a public health priority of the first order. As described above, preliminary results from a University of Iowa study suggest that MRSA has been found in U.S. hogs and in workers on those hog farms. However, we do not know the full extent of the problem as the U.S. government is not systematically testing U.S. livestock for MRSA.

While it may seem as simple as searching out antibiotic-free meat and dairy products, the situation is much more complex.  That may reduce the use of non-therapeutic dosages of antibiotics in the industry, but the antibiotic-resistant bacteria will continue to spread.  Your food will not necessarily have less harmful bacteria on it.  You will still have to practice good home food safety practices.  The bigger question, in my opinion, is how are the overall husbandry practices of the animal producer?  What suite of practices are they putting into place to reduce stress, reduce illness and disease, reduce pathogenic bacteria, and promote healthy growth, without the use of routine antibiotic use?

Comments

[Exeter Adrochen]

Why not eat just plant food you ask...?

1) Plants can harbor disease too. Perhaps you missed the sickening spinach, peanuts, peppers, pistachios. You might say, do not eat plants from big ag but just do the same with meat and you have the same great benefits.

2) A vegan diet is not sustainable everywhere. Veganism requires supplements in the form of pills and/or long distance transport of vegetables. Perhaps you are going to start telling people they must live only in parts of the world where they can grow local veggies year round? How authoritarian.

3) Are you not aware that growing veggies kills large numbers of animals and destroys large amounts of habitat? Clearing fields, plowing, disking, harrowing, planting, weeding, harvesting all kill billions of animals. Educate yourself. That lettuce isn't guilt free. Even if you simply forage you're stealing from the animals - for shame.

4) Livestock can be raised on pastures that are not otherwise suitable for growing crops. This makes good use of our land. The animals are turning sunshine, carbon dioxide, nitrogen, water and minerals into high quality proteins and lipids. Meat is a very high quality food. It is part of a good diet.

5) Livestock produce valuable manure. Without that you can't grow organic veggies as well. Plant composts alone are not nearly as good.

6) Life is a food web. We are part of it. Ethics and morality are simply distractions you're using to justify your choices. Fine for you to do for yourself but don't try and force it on other people.

Go omnivores - a sustainable diet we're evolved for!

[Bradys Beef]

It's too bad more farms don't raise animals in a more natural environment so antibiotics aren't needed. Our grass-fed cows are almost never sick.

[aman]

WHAT IS THE BACTERIA NAME WHICH LIVE IN A PIG?

[Christopher Barden]

Rebecca,

Why not just eat plant-based foods?

I read this whole post and, if I weren't vegan already, content like this would encourage me to do so.

I'm an ethical vegan, so I wouldn't eat meat or dairy even if it were 100% safe.

But, the problems you describe here are now being repeated worldwide. In China, where I live, the "Americanization" of the meat and dairy industries is full-speed ahead, with no possibility of slowing anytime soon.

Seriously, what you're talking about here seems enough to motivate EVEN a non-vegan to go vegan as a form of symbolic protest to raise awareness.

[Gary Maxwell]

Rebecca, you nailed it with the bigger question of ethical livestock husbandry practices. Broad-scale administering of antibiotics leads me (as an untrained layman) to believe that the farmer (a) lacks skill or time to evaluate the health of the livestock on a daily basis, (b) hates to pay for professional veterinary services, (c) maintains livestock in an unhealthy environment, (d) won't accept that disease happens in a natural environment, (e) consumes too much Kool Aid from Big Pharma, or some combination of the above. As a consumer, this is both sad and scary.