Researchers discover worrying new antibiotic-resistance gene variant

A new variant of a human gene which is known to cause significant drug resistance in patients has been discovered by a team of Chinese researchers in a routine medical examination. Even worse, the subject found to be carrying the new gene variant was healthy, meaning the variant may be present in many other healthy carriers who are unknowingly spreading the drug resistance.

The original gene mcr-1 is already well-known, causing resistance to polymyxin antibiotics, a grade of treatments which are often employed as a last-ditch effort to tackle multidrug-resistant bacteria, among others including colistin. However, it is feared that this new variant, named mcr-1.6, could lead to a surge in resistance to colistin, resulting in greater doses of the drug to be used in last-line treatments.     

The gene was identified in salmonella, a food-borne pathogen – a trait which is not seen in any other members of its class. "This is the first time an mcr-1 gene has been found in Salmonella in a healthy carrier," said Biao Kan, Professor of Pathogenic Microorganisms and Infectious Disease Control, National Institute for Communicable Disease Control and Prevention, at the Chinese Center for Disease Control and Prevention. "Salmonella infections have been the leading cause of foodborne illness, and Salmonella-carrying mcr-1 will likely be a problem in food safety."

Resistance genes are often transmitted via plasmids, which are able to move across a range of bacteria species. Khan also notes that in mcr-1.6’s case, the plasmid has a high rate of transmission across a wide variety of hosts, making its discovery particularly significant.