A terrifying, yet not surprising article was published today in The Lancet Infectious Diseases about mcr-1. For those who aren’t familiar with it, mcr-1 is a gene associated with antibiotic resistance to colistin, a type of polymyxin antibiotic used to treat infections that are already resistant to several other types of antibiotics. News sources have been spreading the word about this discovery just like an infectious disease outbreak (see here, here, and here). The key findings of their study are as follows:
- It is confirmed that the mcr-1 gene is responsible for colistin resistance. The authors report that, “In an in-vivo model, production of MCR-1 negated the efficacy of colistin”.
- The mcr-1 gene is located on a plasmid and therefore can move easily between cells. This means mcr-1 has the potential to spread colistin resistance extremely fast. As stated in this paper, “The plasmid carryingmcr-1 was mobilised to an E coli recipient at a frequency of 10âˆ’1 to 10âˆ’3 cells per recipient cell by conjugation.
- Numerous animals and people in China were found to already have E. coli with the mcr-1 gene. As the authors report, “We observed mcr-1 carriage in E coli isolates collected from 78 (15%) of 523 samples of raw meat and 166 (21%) of 804 animals during 2011—14, and 16 (1%) of 1322 samples from inpatients with infection.”
Taking a step back, what does the paper really mean? The universal fear of a superbug is becoming a reality and it will take a global effort to combat it. First and foremost, agricultural use of polymyxin antibiotics needs to stop immediately. Not only does the continuous use of them create an environment that selects for resistant bacteria, but also agricultural use is one of the fastest way to spread resistance as it travels to people (farmers and consumers alike), other animals, soil, and water systems. If only laws moved as fast as bacteria can gain resistance to antimicrobials. Historically, it takes the government to enforce regulation of antibiotic use and years for it to go into effect. If we have learned anything, we need to stop overusing antibiotics now instead of waiting for them to be legally banned. This applies to all antibiotics, not just colistin that was featured in the aforementioned paper. We will soon be in a too little, too late scenario if we aren’t already.