New data on antibiotic resistance in agriculture, released Friday by agencies of the European Union, demonstrate how complicated it is to control all the uses of antibiotics on farms and to prevent all the side effects of antibiotic use.
The findings are discouraging, because Europe has done more than any other political jurisdiction to restrict antibiotic use on farms. And they may amount to a warning for the United States, which in January will finalize voluntary moves by the FDA to limit some farm antibiotic use here.
The data released Friday come from the European Food Safety Authority and the European Medicines Agency, and were released as part of European Antibiotic Awareness Day, a multi-country event that warns of the dangers of antibiotic resistance.
Both sets of data show that Europe is struggling to control the use of colistin, an old antibiotic that until recently wasn’t used in humans because it is too toxic. When medicine abandoned the drug, agriculture picked it up — but as antibiotic resistance got worse around the globe, medicine began to use colistin again, to cure antibiotic-resistant infections that no other drug could cure.
Then, in November last year, British and Chinese researchers revealed that colistin-resistant bacteria were flourishing in farm animals, retail meat and hospital patients in China. Subsequently, more than 30 countries found a gene that confers that resistance, called MCR, in livestock, meat or people, including four people (and two pigs) in the U.S.
Those discoveries raised fears that the last-resort drug would no longer be effective when needed for grave infections, because animals and meat were spreading resistance in a way that was not being tracked. And those fears caused governments to begin trying to determine whether colistin resistance was occurring in their jurisdictions.
One set of numbers released Friday reported the results of one such search. The European Food Safety Agency (EFSA), which routinely looks for antibiotic resistance in food-borne bacteria such as salmonella and campylobacter, began looking for colistin resistance even before the news from China was published. In 2014, it imposed a requirement that national governments report any identification of colistin resistance in their livestock.
Adding up data from across the EU, the agency found colistin resistance in 0.9 percent of E. coli collected from broiler chickens and 7.4 percent collected from turkeys. It also found resistance in 8.3 percent of salmonella strains collected from broilers, 4.4 percent of those collected from chicken meat and 24.7 percent from turkey meat.
Though low, those numbers are surprising given that for 10 years Europe has led the world in restricting farm antibiotic use. At the end of 2005, the European Commission banned the use of growth promoters, micro-doses of antibiotics that are given routinely to broilers, pigs and beef cattle to help them put on weight. That ban was put in place because of worries about antibiotic resistance, but colistin use and colistin resistance slid through a loophole. Colistin isn’t used for weight gain, and so it wasn’t covered under the rules.
“We don’t use growth promoters in Europe, but in some cases this has led to use of other antibiotics in a prophylactic way,” Dr. Marta Hugas, of the EFSA, told me.
A second set of data released Friday shows how farmers have needed antibiotics to prevent certain diseases that occur in close quarters. The European Medicines Agency (EMA) revealed that in 2014 colistin made up 6.6 percent of total veterinary sales of antibiotics in Europe, up from 6.1 percent the year before.
That total is rising, Dr. Helen Jukes, of the EMA, said, because there are few antibiotics left that still work to prevent infections, particularly of E. coli, in livestock. Most of the drugs that were previously used have already become less effective due to the development of resistance, and the ones that remain effective are ones that the World Health Organization wants protected because they are used to cure human infections as well.
For the United States, there are good and bad implications in this new European data. The good: At the moment, colistin isn’t used in livestock here. However, that hasn’t stopped colistin resistance from appearing in people, and the Centers for Disease Control and Prevention has not been able to determine how it entered the country.
The bad: Colistin resistance is occurring in Europe despite the ban on growth promoter use, because the EU did not think to control preventive use of antibiotics. The rules that will restrict the use of growth promoters in the U.S. after December also do not ban preventive use. Here, as in the EU, that leaves a loophole through which resistance might enter.
Europe is beginning to grasp that problem, and EU agencies are formulating new rules to curb what they can. Colistin resistance “is an alarm for global action,” Hugas said. “One country cannot do it alone.”
Maryn McKenna is a National Geographic contributor, and the author of Superbug and Beating Back the Devil. She last wrote for FERN about how the Netherlands cut antibiotic use on farms. Her new book on antibiotics in agriculture will be published by National Geographic Books/Penguin Random House in 2017. She will be writing regularly about antibiotics and agriculture for Ag Insider.