February 8, 2017
Bacteria resistant to colistin, the so-called last resort antibiotic, are probably being transferred to humans from poultry farms in China, say researchers, adding to fears that time to develop new types of medicine is running out.
The 2015 discovery in China of bacteria with mcr-1, the colistin resistance gene, sparked fears over the future of human health. Margaret Chan, head of the World Health Organization, said last year that medicine risked “going back to the dark ages” without action to spur development of new antibiotics and to preserve the dwindling numbers that remain effective.
Since the discovery in animals on farms where colistin was widely used as a growth enhancer, bacteria with mrc-1 have been identified in more than 30 countries including the US, Germany, Spain, Thailand and Vietnam. A patient in the US was found to have been infected with e-Coli carrying the gene last year.
Developed for clinical use in 1959, colistin was little used on human patients because of side effects including kidney damage. But it has been thrust under a spotlight as resistance to the more commonly used family of last-resort antibiotics known as carbapenems has risen, provoking alarm among health professionals.
E-Coli bacteria with the mcr-1 gene were found among patients at Chinese hospitals in two large cities, according to a study in the Lancet last month. The incidence of resistant strains was around 1 per cent, the researchers said. “The emergence of mcr-1 heralds the breach of the last group of antibiotics,” said Professor Tim Walsh of Cardiff University, one of the paper’s authors.
According to a separate paper published this week in Nature Microbiology, the same team found high rates of bacteria with colistin resistance genes in flies at poultry farms in China, suggesting the insects could spread resistance.
“There is a higher rate of incidence among people living close to farms,” said Jianzhong Shen of the China Agriculture University, one of that paper’s authors. “That’s an interesting result. Flies and migratory birds are probably important modes of transmission. Drug-resistant genes can be transmitted through the environment, through the animal food chain and to humans.
“It is a warning that in animal breeding we must use antibiotics sparingly, and ensure that facilities are kept clean to cut the chain of transmission,” Dr Shen added.
Some bacteria the researchers found in flies and in poultry for sale in Chinese markets carried bacteria resistant to both colistin and carbapenem, raising the risks of “super bacteria” resistant to several kinds of last-resort antibiotics.
Yu Yunsong of Zhejiang University co-authored a separate study published in the Lancet last month that found mcr-1 and carbapenem-resistant bacteria in samples from 28 Chinese hospitals, but said it was “too early to say that super bacteria resistant to all antibiotics are imminent”.
China reacted to the discovery of colistin-resistant bacteria on farms by banning the use of the drug as a growth stimulant for animals last year. But its use to treat sick animals is not restricted, and Chinese hospitals plan to begin using it to treat human patients this year. Dr Yu said that efforts to reduce the rampant over-prescription of antibiotics in Chinese hospitals, which are dependent on drug sales for revenues, are beginning to see results.
China is the world’s top producer of colistin, with Hebei province in the north home to the world’s largest factory producing the antibiotic, with output capacity of 10,000 tonnes a year for domestic use and export. Despite the ban the Financial Times was able to find several Chinese websites selling colistin for agricultural use.
Twitter: @hancocktom
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