Alarm over 'superbug' gene found in bacteria

Scientists call for urgent curbs on use of a class of antibiotics in livestock farming

LONDON • A new gene that makes bacteria highly resistant to a last-resort class of antibiotics has been found in people and pigs in China - including in samples of bacteria with epidemic potential.

The discovery was described as "alarming" by scientists, who on Wednesday called for urgent restrictions on the use of polymyxins - a class of antibiotics that is widely used in livestock farming.

"All use of polymyxins must be minimised as soon as possible and all unnecessary use stopped," said Professor Laura Piddock, a professor of microbiology at Britain's Birmingham University.

Researchers led by Professor Liu Jian Hua from the South China Agricultural University who published their work in the Lancet Infectious Diseases journal found the gene, mcr-1, on plasmids, which are mobile DNA that can be easily copied and transferred between different bacteria.

This suggests "an alarming potential" for it to spread and diversify between bacterial populations, they said.

The discovery of the spreading mcr-1 resistance gene echoes news from 2010 of another so-called "superbug" gene, NDM-1, which emerged in India and rapidly spread around the world.

The team already has evidence of the gene being transferred between common bacteria such as E. coli, which causes urinary tract infection, and Klesbsiella pneumoniae, which causes pneumonia .

This suggests "the progression from extensive drug resistance to pan-drug resistance is inevitable", they said. "Although currently confined to China, mcr-1 is likely to emulate other resistance genes... and spread worldwide."

The discovery of the spreading mcr-1 resistance gene echoes news from 2010 of another so-called "superbug" gene, NDM-1, which emerged in India and rapidly spread around the world.

Prof Piddock and others said global surveillance for mcr-1 resistance is now essential to prevent the spread of polymyxin-resistant bacteria.

China is one of the world's largest users and producers of colistin for agriculture and veterinary use.

Worldwide demand for the antibiotic in agriculture is expected to reach almost 12,000 tonnes per year by the end of this year, according to a report by the QYResearch Medical Research Centre.

In Europe, 80 per cent of polymyxin sales are in Spain, Germany and Italy, said the European Medicines Agency's Surveillance of Veterinary Antimicrobial Consumption.

For the China study, researchers collected bacteria samples from pigs at slaughterhouses across four provinces, and from pork and chicken sold in 57 markets in Guangzhou, between 2011 and 2014. They also analysed bacteria from patients with infections at two hospitals in Guangdong and Zhejiang.

They found a high prevalence of the mcr-1 gene in E. coli samples from animals and raw meat. The proportion of positive samples increased from year to year, they said, and mcr-1 was also found in 16 E. coli and K. pneumoniae samples from 1,322 hospitalised patients.

Professor David Paterson and Dr Patrick Harris from Australia's University of Queensland said the links between agricultural use of colistin, colistin resistance in slaughtered animals, colistin resistance in food, and colistin resistance in humans were now complete.

"One of the few solutions to uncoupling these connections is limitation or cessation of colistin use in agriculture," they said. "Failure to do so will create a public health problem of major dimensions."


A version of this article appeared in the print edition of The Straits Times on November 20, 2015, with the headline 'Alarm over 'superbug' gene found in bacteria'. Subscribe