“Factory farms may be ground-zero for drug resistant staph bacteria” – Scientific American

Florida Chicken House photo: Wikimedia Commons/USDA Source: Scientific American

Joseph Stromberg reports for Scientific American about new studies that implicate factory farms that use antibiotics to promote growth in livestock for the increase in antibiotic-resistant bacteria, like MDRSA.

Stromberg begins, “A study found that from 2003 to 2008, the number of people checking into U.S. hospitals with MRSA doubled; moreover, in each of the last three years, this number has exceeded the amount of hospital patients with HIV or influenza combined.”

Also, an increasing number of people are coming in with staph infections that are proving hard to treat, according to Stromberg.  This raises the question, where are these antibiotic-resistant bacteria coming from.  He writes:

Many scientists believe that the problem can be traced to a setting where antibiotics are used liberally: industrial-scale livestock operations. Farm operators habitually include antibiotics in the feed and water of pigs, chickens and other animals to promote their growth rather than to treat particular infections. As a result, they expose bacteria to these chemicals on a consistent basis. Random mutations enable a small fraction of bacteria to survive, and constant exposure to antibiotics preferentially allows these hardier, mutated strains to reproduce.

From there, the bacteria can spread from the livestock to people who work in close contact with the animals, and then to other community members nearby. Previously, scientists have found MRSA living in both the pork produced by industrial-scale pig farms in Iowa and in the noses of many of the workers at the same farms.

Now, a new study makes the link between livestock raised on antibiotics and MDRSA even clearer. As published today in PLOS ONE, workers employed at factory farms that used antibiotics had MDRSA in their airways at rates double those of workers at antibiotic-free farms.

This study, conducted by researchers from Johns Hopkins University swabbed the nasal passages of participating workers from among two types of animal farms, “Industrial livestock operation(ILO) and antibiotic-free livestock operation(AFLO),” in North Carolina, according to the published study.[Click here for peer reviewed study published at Plosone.org]

The study participants’ names and the names of the farms where they work were kept secret for fear of job-loss or repercussions.   Stromberg describes the findings:

The scientists also swabbed the nasal cavities of the workers and cultured the staph bacteria they found to gauge the rates of infection by MDRSA. As a whole, the two groups of workers had similar rates of normal staph (the kind that can be wiped out by antibiotics), but colonies of MDRSA—resistant to several different drugs typically used as treatment—were present in 37 percent of workers at industrial farms, compared to 19 percent of workers at farms that didn’t use antibiotics.

Perhaps even more troubling, the industrial livestock workers were much more likely than those working at antibiotic-free operations(56 percent vs. 3 percent) to host staph that were resistant to tetracycline, a group of antibiotics prescribed frequently as well as the type of antibiotic most commonly used in livestock operations. [Emphasis added]


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