August 26, 2015
We’re almost getting used to it by now: chicken producers and restaurant chains are flocking to get antibiotics out of their food chains. A rash of large food corporations have been announcing their plans to cut the use of human antibiotics in their chickens. Major headlines in the last year include: “McDonald’s Moving to Limit Antibiotic Use in Chickens,” “Perdue Says Its Hatching Chicks Are Off Antibiotics,” “Tyson: Nix Human Antibiotics in Chickens by 2017.”
And it’s a good thing, too: the misuse of antibiotics is of major concern in the ever-escalating problem of antibiotic resistance.
In addition to McDonald’s, Perdue, and Tyson, other companies are being praised for their antibiotic-free meat. Chipotle and Panera Bread were early adopters, followed by big names like Chick-fil-A, Costco, and Pilgrim’s Pride,
This movement in food, driven by consumer demand and industry pressure, appears to be a step in the right direction. But before celebrating this as an imminent victory against antibiotic resistance, let’s put on our skeptics’ hats for just a moment. These corporate efforts are to be applauded, certainly — but do these measures go far enough to protect public health?
The Public Health Crisis
The rise of drug-resistant pathogens — and the lack of new pharmaceuticals to fend them off — is a public health crisis that undermines our ability to fight infection. In 2013, the Centers for Disease Control and Prevention estimated that 2 million Americans acquire serious infections with drug-resistant bacteria every year, leading to at least 23,000 deaths. The misuse of antibiotics in both medicine and food production is the biggest factor that leads to resistance.
“The strong survive when you have a selective pressure, and I don’t know of a stronger selective pressure in the bacterial world than antibiotics,” said Lance Price, a professor of environmental and occupational health at The George Washington University and a CLF-Lerner Fellow.
Because antibiotics kill or slow the growth of bacteria, any organisms that can resist their effect will outlive their peers. They weed out the weak and allow the strong to proliferate.
When chicken producers feed their birds antibiotics or put them in the drinking water, the animals end up developing drug-resistant bacteria in their guts. When slaughtered, that bacteria can contaminate the meat, and any humans who don’t handle or cook the meat properly can get an infection. Another serious pathway of infection is from animals on the farm to people living and working in the farm community. Drug-resistant bacteria also can spread through environmental exposure, for example when the animals’ feces is used as fertilizer or contaminates the water used for food crops.
The Fine Print: “Human Antibiotics” and Ionophores
In their announcements, companies like Tyson were careful in making a distinction between phasing out the use of human antibiotics versus all antibiotics in their flocks. Human antibiotics are also sometimes referred to as “medically important antibiotics” — essentially, the drugs we use to treat human infections. Currently, up to 70% of medically important antibiotics sold in the U.S. are given to food animals, not people.
However, the chicken producers have stated that they will still use a so-called “animal-only” class of antibiotics called ionophores. Ionophores don’t work well in humans. But they do work in animals, and the producers who continue to use ionophores with their livestock cling to the hope that our “human antibiotics” won’t be negatively affected by bacteria that build up resistance to ionophores.
But is this really true? The answer is still up for debate. Microbiologist Stuart Levy, Director of The Center for Adaptation Genetics and Drug Resistance at Tufts University, is happy to see companies taking strides in the right direction — but any claims that ionophores definitely do not add to antibiotic resistance for humans are yet unfounded.
“Any antibiotic will change the microbial environment in which it’s being given,” said Levy. “You don’t need any antibiotics for food production because I think there would be no control over the drug selection. As in, you could get multidrug resistance from the prolonged use of a single drug.”
In other words, using a single antibiotic could actually select for bacteria that are resistant to multiple antibiotics too. He cites as an example from his study on a farm where chickens were fed tetracycline-supplemented feed. Administering the antibiotic ended up promoting resistance in their gut bacteria, not just to tetracycline, but also to multiple other types of antibiotics such as streptomycin and ampicillin.
Keeping Up with Science?
Multidrug resistance was found in more than half of the E. coli strains found in the chickens, and the genes responsible for tetracycline resistance were linked to those that provided resistance to the other antibiotics. To be safe, Levy believes chicken producers must rid their farms of all antibiotics, including ionophores.
To be fair, some companies are trying hard to keep up with the science: Perdue, in a statement released on July 8, said it is attempting to reduce the amount of animal-only antibiotics as well as human antibiotics, claiming that now 42 percent of flocks receive no antibiotics of any kind. (Recently, The New York Times wrote about Perdue’s commitment.)
“We’re looking for alternatives — antibiotics that aren’t really acting as antibiotics, but as other inhibitors of growth which are not classified as antibiotics because they don’t play in the same ball field,” he said.
Vertical Transfer: Breeder Chickens May Contaminate Eggs
Another possible gap in recent corporate efforts focuses on the elusive breeder companies that sell fertile eggs to Perdue and other poultry producers to be hatched and raised. Because breeder chickens never enter the food supply, that portion of the poultry production system is more or less a black box in terms of antibiotic use. Could they be contributing to antibiotic resistance as well?
Susan Vaughn Grooters, a policy analyst for public health coalition Keep Antibiotics Working, is concerned about this type of inherited resistance that passes from generation to generation of birds.
“The way we’re looking at poultry production, we tend to look at it from hatch-on, as opposed to looking at breeders,” Grooters said. “That’s a gap in our knowledge, but it’s also a gap in policy because we’re not monitoring antibiotic use in different points in production. If we want to understand how antibiotic resistance emerges, we need to look at all points of the production chain.”
Through a phenomenon called vertical transfer, eggs and the resulting chicks can end up contaminated with some bacteria from the hen laying them. So if breeder chickens are being fed loads of antibiotics and passing on those drug-resistant bacteria either to nearby humans or to the chickens that end up in our grocery stores, they are effectively bypassing any efforts made by poultry producers to cut down levels of resistance.
Grooters suggests that, to cover all their bases, major retailers and restaurant chains should specify to chicken suppliers that any of their breeders must provide evidence of being raised antibiotic-free as well.
Lastly, the push towards antibiotic-free food production needs to go beyond just poultry. Companies have started with chicken because of their shorter length of life, so producers have more control over how that animal can be raised. Also, chicken houses are often owned by or under contract with companies they are supplying to, so they have to meet a certain standard dictated by the higher-ups. In comparison, this kind of vertical integration has lagged behind for the pork industry and particularly the beef industry.
This doesn’t mean that swine and cattle are off the hook, says Grooters, but major supply line changes will need to happen in order to make more of those meats antibiotic-free.
“Tyson produces 2 billion chickens, and that’s a big dent in the 9 million that we raise, but we need more than that,” said Price. “It’s not just chickens — it’s turkeys, pigs, and cattle.”
All in all, experts can agree that these strides to reduce antibiotic use by corporations are commendable — but they really are just the first step. The remaining chicken producers need to follow suit, including breeders. Pork, cattle, and other food animals may be tougher industries to crack for logistical reasons, but consumer demand may pressure them to jump on the antibiotic-free bandwagon. Eventually, phasing out antibiotics could likely inspire better animal husbandry, environmental cleanliness, and improvements in production practices.
Image by Alexander Winch, 2015.
This work by Meeri Kim and the Johns Hopkins Center for a Livable Future is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Based on work at www.livablefutureblog.com. Images in this post are included in the Creative Commons license.