Last week, I shared scary news of a new gene called mcr-1 conferring resistance to our last-ditch antibiotic, colistin. The gene was found in China with spread to the Netherlands. I raised concerns, too, about imports of some foods from China.
Several new reports in the Lancet Infectious Diseases suggest the spread of this newly found resistance gene, mcr-1, is far worse than it initially appeared. Here are the latest findings from several just-released studies.
In some ways the most disturbing to me was the part of the “COMBAT” study that looked at how often Dutch travelers picked up the highly resistant superbug ESBL (that I’ve written about here). Researchers took stool samples from 2,001 travelers before and after their trips. Disturbingly, they found that 34% of the travelers acquired ESBL-producing Enterobacteriaceae after trips of 1-6 weeks’ duration. Nine of these travelers had a colistin-resistant ESBL isolate, and the mcr-1 resistance gene was found in six of the nine. (Resistance in the others occurred by different mechanisms). Interestingly, 5/6 had developed traveler’s diarrhea; none had taken any antibiotics. These unrelated travelers had apparently acquired their resistant genes during visits to Peru, Bolivia, China, Tunisia, and SE Asia, suggesting that the mcr-1 colistin resistance gene has been circulating for some time, undetected.
Other Chinese researchers have come to that same conclusions about occult, asymptomatic colonization and dissemination, finding the mcr-1 gene in several human gut microbiome samples, which they describe as an antibiotic resistance gene reservoir.
While the initial mcr-1 colistin resistance was found in E. coli bacteria, another study from the Netherlands’ COMBAT consortium of universities found that an identical mcr-1 gene was also found in a Salmonella enterica serotype Typhimurium isolate from a food sample in Portugal, almost identical to those found previously in southern China. This suggests both that there may be a broader range of bacteria that can be affected by this plasmid, and again that the geographic spread is far broader.
Similarly, French researchers screened E. coli isolates from pigs, people and poultry from Laos, Thailand, France, Nigeria and Algeria. They found the mcr-1 gene in isolates from each of those countries, including a strain that had been transferred from a pig to a farmer. They warn that the spread is likely worse, especially in Africa, where colistin is widely used in livestock production.
Meat production
Last week, I noted that China has heavy colistin use in its agriculture industry, and that this raises concerns about meat imports into the U.S. Polymyxins (the colistin class) are also heavily used in Europe. The U.S. imports small amounts of beef from Denmark and Croatia, and considerable pork from Poland and Denmark. Millions of head of cattle and hogs are imported, mostly from Canada and Mexico. (In June, 2015, the House voted to repeal the requirement for country-of-origin labels [COOL] on beef, pork and chicken sold in the U.S. as part of a World Trade Organization dispute with Canada and Mexico. This is still pending in Congress.
Besides allowing labeling, the first thing experts agree on is that we must immediately stop the use of widespread use of colistin in animals as a growth promoter. The drug should either be banned outright, or have severely restricted use for ill animals.
Implications
What does all this talk about resistance genes and WTO fights mean to you?
First, the cat’s out of the bag. The mcr-1 gene has now been found in veterinary, meat and food samples, and human stool samples from four continents. Lance Price, Director of the Antibiotic Resistance Action Center at George Washington University, notes that the insidiousness of the spread “underscores the critical need for real, integrated surveillance between hospitals, communities and livestock” industries. He added to me, “We have no regulatory tools to stop the trade of these products” because these bacteria are classified as “normal flora” and not pathogens, as E. coli O157 is.
It appears to me that the food industry lobbyists are seemingly as busy and successful as the NRA. Unless regulators stand up to strong-arm tactics, we will soon begin to see deaths from these new untreatable superbugs grow and threaten us just as the senseless gun deaths do.
