Here at The Salt, we've been following the controversies that surround antibiotic use on the farm. Farmers give these drugs to chickens, swine and beef cattle, either to keep the animals healthy or to make them grow faster. Critics say it's contributing to an epidemic of drug-resistant bacteria not just on the farm, but among people, too.

Today, the Centers for Disease Control and Prevention released a report on that epidemic. For the first time, the agency came up with a ranking of the threats posed by different drug-resistance microbes, listing them as "urgent," "serious," and "concerning."

And where in this ranking did farm-related antibiotic resistance fall? Not at the top, certainly. According to the CDC, the most urgent threats are posed by antibiotic-resistant infections that have emerged in hospitals, as a result of heavy antibiotic use there. These include infections with Klebsiella and E.coli bacteria that are resistant to every known antibiotic, as well as drug-resistant gonorrhea.

"Right now, the most acute problem is in hospitals," said Tom Frieden, the CDC's director, in a conference call with reporters. "The most resistant organisms in hospitals are emerging in those settings because of poor anti-microbial stewardship among humans."

"That having been said," he continued, "any widespread use of antimicrobials increases the risk" that resistance to those drugs will spread. The report lists in its "serious threat" category several kinds of bacteria — notably salmonella and Campylobacter — that have become resistant to drugs that are widely used on the farm, as well as in hospitals. And the report includes a graphic that clearly connects antibiotic use on animals drug-resistant infections in humans.

Critics of antibiotic use on the farm had mixed reactions to the report. The Center for Science in the Public Interest sounded disappointed, saying that the CDC "missed an opportunity" to issue clear recommendations on reducing antibiotic use in animal production.

Two other groups — the Pew Campaign on Human Health and Industrial Farming and the Natural Resources Defense Council — praised the report for clearly stating that drug use on the farm adds to the problem of antibiotic resistance, even if it may not be the most important cause of that problem.

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