The lower infection rate among huma

The lower infection rate among humans almost certainly means that the resistant bacteria passed from animals to humans, the study found.
It said that while mcr-1 was "currently confined to China" it was likely to spread globally.

"This is a worrying report, as polymyxins are often the last resort antibiotic to treat serious infections," said Laura Piddock, a professor of microbiology at the University of Birmingham.
"Equally worrying is that this type of resistance can be easily transferred between bacteria."

Other types of drug resistance -- such as for tuberculosis -- show that "this likely paves the way for it to spread throughout the world," she added.

Some 480,000 people contracted multi-drug resistant tuberculosis in 2014, according to the WHO. The disease killed 190,000 in the same year.
Professor Timothy Walsh of the University of Cardiff, who collaborated on the study, told the BBC News website antibiotics could soon become useless.

"If MRC-1 becomes global, which is a case of when not if, and the gene aligns itself with other antibiotic resistance genes, which is inevitable, then we will have very likely reached the start of the post-antibiotic era," he said.

"At that point if a patient is seriously ill, say with E. Coli, then there is virtually nothing you can do."

The study will renew debate about the use of colistin in animal husbandry, researchers said.

"The finding that this type of resistance can be shared by different bacteria -- irrespective of whether from food, an animal or a person -- is further evidence that the same drugs should not be used in veterinary and human medicine," Piddock said.