Just two months ago, researchers in China identified a gene that can make bacteria resistant to a last-resort antibiotic called colistin. It was a bombshell discovery for people who follow superbugs. Now that gene has been detected in at least 19 countries, and scientists are alarmed.
Colistin is what doctors give you in the U.S. when nothing else works. Because it’s toxic, it can have some harmful side effects, but colistin can help defeat infections that shrug off every other antibiotic in their arsenal. If bacteria resist everything, including colistin, you’re out of luck.
Since the paper identifying colistin-resistant E. Coli in China was published in the Lancet Infectious Diseases journal on Nov. 18, the gene has been detected in 19 countries in bacteria from farm animals, retail meat, or humans, according to a new tally by the Natural Resources Defense Council, which advocates for reducing the use of antibiotics in farm animals. It is in Southeast Asia, Europe, Canada, and Japan.
That doesn’t mean the gene, known as MCR-1, has spread to all those places in two months. Scientists are finding it retrospectively in older samples of bacteria now that they know what to look for. In Denmark, for example, the gene was found in bacteria from food inspections as far back as 2012, when the current system of monitoring was started.
Antibiotic-resistant bacteria sicken 2 million Americans each year and kill 23,000, according to estimates from the Centers for Disease Control. These are such bugs as CRE (Carbapenum-resistant Enterobacteriaceae) or MRSA (Methicillin- resistant Staphylococcus aureus). It’s not clear how many people are affected by colistin-resistant strains. The gene hasn’t been identified in samples from the U.S. yet.
But scientists fear that colistin-resistant bugs will become more widespread. The bacteria themselves can travel on people, live animals, and food. The gene that makes a bug resistant to colistin is particularly slippery because it can jump easily from one type of bacteria to another.
“I say it’s shopping for a home,” said Lance Price, a professor of environmental and occupational health at George Washington University. “The thing that really frightens a lot of us is that it’s going to find its way into a bacterium that’s resistant to everything but colistin,” he said.
That’s a dark scenario. Colistin is used to treat the kind of infections that the CDC calls “nightmare bacteria,” which kill half the people who get them. These bugs typically spread in health-care settings whose patients are already vulnerable, though healthy people can carry the bacteria in their gut without knowing it. Add to the mix colistin-resistance, conferred by a gene that’s easy to spread, and the nightmare gets worse. “We have the fuel to set off a fire,” Price said.
I asked him how worried we should be. “I don’t want to be a fearmonger,” he said, but the November paper “sort of ruined my Thanksgiving.”
Drugmakers used the World Economic Forum in Davos this week to call for more investment to develop new antibiotics. The NRDC says widening resistance to a last-resort medicine is the latest urgent warning that the world needs to use the medicines we have more carefully, particularly in raising livestock. The drugs are widely deployed on industrial-scale farms, not just to treat sick animals but to prevent disease and promote faster growth.
Price agrees. “When you misuse antibiotics in food animal production, there are major potential risks to human health,” he said. Colistin isn’t used in farm animals in the U.S., but it is used in China and elsewhere.
The U.S. government and food companies responding to pressure from consumers have taken some halting steps to curbing antibiotic use in American livestock. The challenge of drug-resistance, though, is similar to climate change: It requires big, coordinated actions on a global scale. A superbug fostered by one country’s loose practices can arrive in another in a shipping container of beef or in the gut of a traveler getting off a plane.
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