Antibiotic resistance is estimated to cause 10 million annual deaths by 2050, exceeding even the 8.2 million that cancer is estimated to cause.

According to a paper in the Lancet, China, as part of its efforts against antibiotics overuse, will cease its use of a last-resort antibiotic, colistin, in animal feed by the end of April 2017, and start using the drug for human therapy. However, some researchers fear that it may be too late.

Resistance to last-resort antibiotic has been discovered

Ever since the 1940s, antibiotics have been used extensively, even indiscriminately, both in humans to treat illnesses, and in livestock, to promote growth and prevent disease. As a result, antibiotic resistance - where harmful pathogens show resistance to antimicrobial drugs – has emerged as a global problem.

Carbapenems are a class of antibiotics often used to treat infections caused by multidrug-resistant bacteria, but resistance to it has built up around the world.

The antibiotic colistin, on the other hand, is one rarely prescribed to humans due to its severe side-effects which include kidney damage. Hence, it is generally effective as a last resort when all other treatment options have failed.

China has been using colistin in animal feed for decades, and the effects are beginning to emerge. In 2015, a colistin-resistant gene, mcr-1, was discovered in bacteria detected in humans and food in China.

As it spreads alarmingly easily among different strains of bacteria, it has been found in multiple countries, including the US and Denmark.

Shift to human use may spread infections to hospitals instead

China’s animal-feed ban, which will see 80,000,000 kilogrammes of colistin withdrawn from the meat and poultry sector, may still be an insufficient measure.

Currently, the gene is not as common in bacteria in clinical settings, but, there is already “colistin resistance in the farming sector at a very high level”, according to microbiology professor Timothy Walsh at the University of Cardiff, one of the discoverers of the gene.

Colistin is still approved for treating sick animals, something that Walsh advises against.

Walsh was also one of the participants in the Lancet study, which examined the prevalence of the gene in bacteria in two of China’s hospitals, along with the risk factors for their presence. The worry is that China’s decision to introduce human use of colistin will favour the spread of colistin-resistant infections in clinical settings.

At the moment, China has not yet announced clear plans on how it will instruct doctors on the use of colistin.

Though Walsh concedes it is likely that China, too, will reserve colistin for the emergency, hard-to-treat cases, China already has a problem with carbapenem-resistant gut bacteria “enterbacteriaceae”.

Measures need to be taken to delay “doomsday scenario”

It is likely that Chinese doctors, despite their best efforts, will find themselves turning more and more frequently to the use of colistin.

“China has a growing problem in carbapenems-resistance, so you are running out of options,” says Walsh.

It could speed the arrival of “the doomsday scenario of convergence of carbapenem resistance and colistin resistance (via mcr-1)”, according to a commentary published with the study. This has dire implications for the rest of the world, as the development of new antibiotics has stagnated.

Yet, there are still some measures that can be taken to delay the emergence of new superbugs resistant to both types of antibiotics.

The first is the prudent use of colistin, “Test people beforehand, to see if they have the mcr gene before [doctors] prescribe colistin,” says biological sciences professor Michael Gillings of Australia’s Macquarie University, who was not involved in the Lancet study.

“The best possible thing is not to use colistin at all,” he added. “But you know, I am not treating a dying patient.” MIMS

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