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Colistin resistance is being found on retail meat. Photograph by Joe Benjamin (CC) on Flickr

Apocalypse Pig Redux: Last-Resort Resistance in Europe

Here’s a breaking news follow-up to my recent post on the discovery of resistance to colistin, the truly last last-resort antibiotic, in animals, meat and people in China. A research collaboration shared between George Washington University and the Statens Serum Institute and National Food Institute in Denmark is announcing today that they have found that same resistance factor in stored bacterial samples dating back as far as 2012.

Short version: That resistance to the very last-ditch antibiotic is already spreading globally.

The Antibiotic Resistance Action Center in the Milken Institute School of Public Health at GWU, headed by Lance Price, PhD, says in an emailed statement:

The news that the dangerous colistin resistance gene has been found in Denmark is alarming. This newly identified gene, called MCR-1, is on a mobile piece of DNA that can make copies of itself and then jump to from bacterium to bacterium, spreading resistance. History shows that these mobile resistance genes can spread around the world quickly, silently riding in people, animals, and food. The news that MCR-1 has been discovered in Denmark suggests that this scenario is playing out in real time.

In their own statement, the Danish researchers say that when they learned of the new resistance factor (published in Lancet Infectious Diseases on Nov. 16), they quickly went back through the stored genomes of bacteria held at their institutions to look for it:

The approximately 3,000 Gram-negative (E. coli or Salmonella) bacteria, which have previously been mapped using whole genome sequencing, have been reexamined to see whether MCR-1 is present. Results show that MCR-1 was found in one patient, who suffered from a blood infection in 2015 and in five food samples that have been imported from 2012-2014. All the bacteria are multiresistant ESBL bacteria containing the MCR-1 gene, which can further complicate treatment.

I’ll add here that the initial article announcing MCR-1 said that this last-ditch resistance might already have spread to Malaysia. After reading that, the pseudonymous blogger Mike the Mad Biologist did a similar search and uncovered that it may have been recorded as early as 2011 in Portugal. (He adds via Twitter that it is not clear where that isolate originated; Portugal is where it was sequenced.)

There’s resonance in this with the initial discovery of NDM in 2008. That was the previous international superbug of concern, which took out the group of antibiotics called carbapenems and left colistin, a toxic drug preserved from the 1950s, as the only one that works. NDM’s source is India, but it was first discovered in a hospitalized man in Sweden.

There will be more to say about this, but for now, here’s how the GWU group end their statement. (I’ll add a link when they publish it. Here it is.)

We must act swiftly to contain the spread of colistin-resistant bacteria, or we will face increasing numbers of untreatable infections. Leaders from every nation should immediately implement a ban on the use of colistin in animal agriculture. While China appears to be the biggest user of the drug, it is approved for use in the the European Union and many other countries. It also is approved for use in food animals in the U.S., but drug companies holding those approvals are not actively marketing the drugs. Drug companies with these approvals should immediately withdraw these label claims to ensure that colistin is never used in U.S. animal agriculture, otherwise our livestock production facilities could become breeding grounds for untreatable superbugs.

In addition, we need to remember why colistin is the last drug available for treating these dangerous infections. We turned to it because the preferred drug class – carbapenems – became powerless against some superbugs due to overuse. Carbapenems are still effective against many bacteria, but for how long? While carbapenems are not approved for use in animal agriculture in many parts of the world, their use is not explicitly banned. World leaders should call for an immediate ban on carbapenems to protect them for future generations.