Gene that makes bacteria immune to last-resort antibiotic can spread

(credit: NIAID/Flickr)

A newly identified gene that renders bacteria resistant to polymyxin antibiotics—drugs often used as the last line of defense against infections—has the potential to be shared between different types of bacteria. The finding raises concern that the transferable gene could make its way into infectious bacteria that are already highly resistant to drugs, thereby creating strains of bacteria immune to every drug in doctors’ arsenal.

The gene, dubbed mcr-1, exists on a tiny, circular piece of DNA called a plasmid. These genetic elements, common among bacteria, are mobile; bacteria can make copies of them and share them with whatever bacteria happens to be nearby. Though scientists have previously discovered genes for polymyxin resistance, those genes were embedded in bacterial genomes, thus were not likely to easily spread.

In a study, published Wednesday in the Lancet Infectious Diseases, researchers in China report first finding the mcr-1 containing plasmid in Escherichia coli bacteria isolated from a pig. The plasmid was solely responsible for the bacteria being resistant to colistin, a type of polymyxin commonly used in animals in China, but less so in the US and Europe. On further examination, the researchers also found mcr-1 containing plasmids in E. coli and Klebsiella pneumoniae isolated from a small number of patients in hospitals in Guangdong and Zhejiang provinces.

Read 6 remaining paragraphs | Comments