Pigs, like other animals raised for food, are often given antibiotics to promote growth and prevent the spread of disease among livestock. Photo by Dusan Petkovic/Shutterstock

GUANGZHOU, China, Nov. 19 (UPI) -- Scientists in China found a gene that makes the common bacteria Enterobacteriaceae resistant to "last-resort" antibiotics, which could pose a serious health risk if passed to other, more dangerous types of bacteria.

Antibiotic resistant germs cause more than 2 million illnesses and 23,000 deaths per year, fueling searches for ways to use fewer antibiotics. Although researchers may have found a combination of drugs could kill MRSA, researchers at South China Agricultural University said their finding points to a gene passed between more common bacteria such as E. coli, potentially a much larger problem.


During a study on antibiotic resistance of E. coli in pigs raised for food, researchers found strains with a polymyxin resistance mechanism, or MCR-1, gene that makes the drugs ineffective against them. Polymyxins are considered the last line of defense when other antibiotics don't work

"The emergence of MCR-1 heralds the breach of the last group of antibiotics," researchers wrote in the study, published in The Lancet: Infectious Diseases. "There is a critical need to re-evaluate the use of polymyxins in animals and for very close international monitoring and surveillance of MCR-1 in human and veterinary medicine."

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Researchers think the bacteria developed resistance because pigs in China are often fed the antibiotic colistin. The resistant bacteria was then passed to people who ate meat from the animals.

"In this case the antibiotic colistin is the 'end of the line' -- the final option for multidrug resistant organisms once all other options have been exhausted," Dr. Bruce Polsky, chair of the department of medicine at Winthrop-University Hospital, told HealthDay. "In order to preserve colistin, as well as other lifesaving antibiotics, the use of antibiotics in animal-feed must be severely restricted in order to reduce the development of resistance among microorganisms which colonize the animals," Polsky said.

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