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The agricultural industry has long been considered an enemy of humanity when it comes to recklessly pumping antibiotics into animals. In further evidence that this practice is fueling a public health crisis, a new study has found a disconcerting trend at Chinese farms: flies are spreading the gene that gives bacteria resistance to our strongest antibiotics, and it’s showing up in hospitalized humans.

At the moment, colistin is considered a last “last resort” antibiotic. It’s primarily used when carbapenems—another “last resort” drug—fail. Unfortunately, the mobilized colistin resistance (MCR-1) gene was discovered in China last year. One US health official suggested that it could be the “the end of the road” for antibiotics. Since then, the gene has been identified in 25 countries, including the United States. This latest study, published last week in The Lancet, indicates that MCR-1 may be spreading faster than we realized, and that some humans are probably unknowingly carrying it.

New Scientist reports:

In a systematic search for colistin and carbapenem resistance in several regions of China, Tim Walsh at Cardiff University, UK and colleagues found colistin resistance in around one per cent of hospital patients in two large cities–even though the drug has not been used to treat people there...

Now we know that the resistance genes probably came from a farm. In a related study, published today, the same team reports that a third of the Escherichia coli bacteria sampled from chicken farms and meat in grocery stores resisted carbapenems, and a quarter of those also resisted colistin.

The scientists found both colistin and carbapenem resistance in dog feces and flies at the chicken farms. That has led them to believe flies are spreading the resistant gene, and raises fears that its potential for spreading is enormous.

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The good news is that China plans to stop feeding 8000 tons of colistin to farm animals (primarily chickens and cows) every year. In April, that short-sited practice will officially be illegal. The bad news is that China will join other nations in using the antibiotic to treat humans, which could further spread the resistance gene. Lance Price, a researcher at George Washington University who has previously studied resistant bacteria in US supermarket meat, tells New Scientist that he fears an “explosion” of infections in humans that are already carrying MCR-1.

The really bad news is that stopping the agricultural industry from using antibiotics is a game of whack-a-mole fueled by pharmaceutical manufacturers who just follow the money. Farmers use antibiotics on their livestock in order to hasten growth and to prevent illness in deplorable conditions. That puts us all in danger. Lead researcher Tim Walsh is afraid that once the Chinese ban kicks in, the pharmaceutical companies will just take their drugs to other places where farmers abuse colistin, like Vietnam. If the trends continue, we’re going to need a new last-last-resort drug that’s hopefully not the last one.

[New Scientist]