CDC Threat Report: Yes, Agricultural Antibiotics Play a Role in Drug Resistance

Campylobacter bacteria. Image: CDC

The grave assessment on the advance of drug resistance, released Monday by the US Centers for Disease Control and Prevention, contained some important observations about the relationship between antibiotic use in agriculture and resistant infections in humans. Those observations, combined with remarks made yesterday by the director of the CDC and also with testimony given in the past by other CDC personnel, ought to put to rest what seems like a persistent meme: that the CDC has never said, or doesn’t believe, that agricultural antibiotic use plays a role in the advance of resistance.

This is important because it puts the CDC in line with a substantial body of research pointing to agricultural use playing a role in the emergence of resistance outside farm properties. With the CDC agreeing — plus, to some degree, the Food and Drug Administration — surely it’s time to move on to whether there are things that could be done to curb the risks posed by some ag practices, while respecting the role that livestock-raising in particular plays as a substantial economic sector, and as an engine in feeding the world.

So, first, yesterday’s report. It includes this language:

  • “Preventing the spread of antibiotic resistance can only be achieved with widespread engagement, especially among leaders in clinical medicine, healthcare leadership, agriculture, and public health.” (p.7)
  • As one of five “Gaps in Knowledge”: “Data on antibiotic use in human healthcare and in agriculture are not systematically collected. Routine systems of reporting and benchmarking antibiotic use wherever it occurs need to be piloted and scaled nationwide.” (p.27)
  • “Antibiotics are widely used in food-producing animals, and according to data published by FDA, there are more kilograms of antibiotics sold in the United States for food-producing animals than for people… This use contributes to the emergence of antibiotic-resistant bacteria in food-producing animals. Resistant bacteria in food-producing animals are of particular concern because these animals serve as carriers. Resistant bacteria can contaminate the foods that come from those animals, and people who consume these foods can develop antibiotic-resistant infections. Antibiotics must be used judiciously in humans and animals because both uses contribute to not only the emergence, but also the persistence and spread of antibiotic-resistant bacteria.” (pp.36-37)
  • “Scientists around the world have provided strong evidence that antibiotic use in food-producing animals can harm public health …  Because of the link between antibiotic use in food-producing animals and the occurrence of antibiotic-resistant infections in humans, antibiotics should be used in food-producing animals only under veterinary oversight and only to manage and treat infectious diseases, not to promote growth.” (p..37)

Out of the 18 drug-resistant organisms the report highlights as alarming, four are foodborne organisms that become drug-resistant as the foods that carry them are produced or grown: Campylobacter (p. 61), E. coli (p. 65), Salmonella (p. 70) and Shigella (p. 75). And finally, the report includes this graphic (p.14); pay attention to the whole left side:

In releasing the report yesterday, Dr. Thomas Frieden, the CDC’s director, said during a media briefing: “For the whole pathway, we need to address from farm to table.  And that at various different steps, there are things that can be done to increase or decrease the likelihood of infections generally and resistant infections specifically. We also know that there are specific situations in which the widespread use of antimicrobials in agriculture has resulted in an increase in resistant infections in humans.”

Frieden also said — and this is not a contradiction to the remark above: “Right now the really most acute problem is in hospitals. And the most resistant organisms in hospitals are emerging in those settings, because of poor antimicrobial stewardship among humans.” The concern with the resistant organisms emerging from agriculture has never been that they are more virulent or more infectious than the resistance which emerges under the pressure of antibiotic use in medicine. Rather, it is that it is a bad idea to encourage the movement of any additional resistance DNA into the microbial traffic that makes up our world — because we have no way of knowing where that resistance will go, or in what bacteria it will end up. (No one, for instance, predicted that resistant foodborne bacteria in chickens would lead to an epidemic of drug-resistant urinary tract infections in the United States and Western Europe.)

Here’s just one example of that problem, a piece of research that came out just as the CDC report was being released and therefore is probably going to slip from notice: an association between the incidence of MRSA skin and soft-tissue infections, and living close to high-density, antibiotic-using hog farms, published online yesterday by JAMA Internal Medicine. (I’ll try to come back to this.)

There are substantial scientific and advocacy communities that have been pushing for change in how agricultural antibiotic use is tracked and regulated, and they had a range of reactions to the CDC’s report. To sum up a few:

  • Dr. David Wallinga, Healthy Food Action: “”CDC has (quietly) said before that antibiotic overuse in food animals helps worsen the epidemic of infections from antibiotic resistant bacteria. But this important report practically shouts it from the mountain top. It’s a clarion for Congress to finally act and do something before — not after — even larger numbers of Americans succumb to these superbugs.”
  • Steven Roach, senior analyst for Keep Antibiotics Working: “We are pleased to see the CDC addressing the issue through a concrete set of recommendations, including phasing out the use of drugs for growth promotion in food animals, putting safeguards in place to prevent infections before they happen, and collecting more data on how antibiotics are used on the farm.”
  • The Center for Science in the Public Interest: “CDC missed an opportunity to advise veterinarians and federal and state agencies on reducing the quantity of antibiotics used in animal production.  Although CDC says antibiotics for growth promotion in food animals should be ‘phased out,’ the report lacks specific detail, including advice for veterinarians, the food industry, and the agencies that regulate food safety.”

Other organizations that commented on the CDC report: the Natural Resources Defense Council (here and here), Consumers Union, and Food and Water Watch.

For more on this, check yesterday’s post on the release of the report: “CDC: We Will Soon Be in a Post-Antibiotic Era.”


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