A bacteria strain that causes a hard-to-treat staph infection probably developed its antibiotic resistance in food animals, a team of scientists announced Tuesday.
The strain of staph, known as methicillin-resistant Staphylococcus aureus, or MRSA CC398, most often infects farm workers who come in contact with infected pigs, turkeys, or cows. The bacteria has been found in about half of meat samples taken throughout the country. The researchers say that the copious use of antibiotics in livestock used for food is to blame for the infection's drug resistance.
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"We can't blame nature or the germs. It is our inappropriate use of antibiotics that is now coming back to haunt us," Paul Keim, one of the study's authors, said in a statement. The researchers believe the bacteria was originally a human strain that was easily treated with tetracycline and methicillin, antibiotics that are regularly pumped into farm animals. Once in the animals, it developed the resistance and was passed back to humans.
The CDC has long said antibiotic use in livestock could be problematic, saying that "the food supply may be a source of antibiotic-resistant genes," but admitting that "quantifying the extent to which this contributes to a food safety problem is difficult."
Now, the researchers seem to have confirmed that without a doubt.
"We are watching this emerge in real time, and it's emerging really quickly," says Lance Price, lead author of the report that will be published in mBio. The strain is also showing the potential to pass from human to human, increasing the chance of an outbreak.
Price says it's unlikely this is the only strain that has developed an antibiotic resistance in animals. "I imagine this has happened multiple times in the past and it'll happen multiple times in the future," he says.
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Doctors are beginning to prescribe fewer antibiotics for fear of creating superbugs, but their use in food animals isn't any less important to drug-resistance development, Price says.
"We have tons of messages out there to tell physicians to stop over prescribing, to tell parents not to ask for antibiotics every time their child has a stuffy nose," Price says. "Meanwhile, we're using 29 million pounds of antibiotics for food production. Those examples couldn't be more polar opposites."
In 2006, the European Union banned the use of antibiotics in livestock for non-therapeutic uses. In the United States, antibiotics are routinely used on livestock to promote their growth and to preemptively treat potential diseases acquired from cramped living conditions. Scientists estimate that approximately 80 percent of all antibiotics are used on livestock.
In Congress, Rep. Louise Slaughter has been pushing legislation that would regulate antibiotic use in animals to be used for food. "I cannot stress the urgency of this problem enough," she said in a statement last year. "When we go to the grocery store to pick up dinner, we should be able to buy our food without worrying that eating it will expose our family to potentially deadly bacteria that will no longer respond to our medical treatments."
Last week, she reiterated the importance of using restraint, asking more than 60 fast-food companies to voluntarily disclose whether they raise their animals with antibiotics or not.
"Very simply, consumers have a right to know what's in their food," she wrote. "It's like that old commercial, 'where's the beef?' We just want to know, 'what's in the beef?'"
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