Many news reports around the world are proclaiming the discovery of a gene that can make bacteria resistant to our “last line of defense” antibiotics will herald a return to the “Dark Ages” of medicine.
The discovery of the gene, dubbed the MCR-1 gene, was found during a routine surveillance project on antimicrobial resistance in commensal Escherichia coli in pigs and chickens. The animals were found to be carrying bacteria resistant to Colistin, an antibiotic used routinely in animal husbandry in China.
“These are extremely worryingly results,” said Liu Jian-Hua, a professor at China’s Southern Agricultural University and co-author of the study. The MCR-1 gene allows bacteria to become resistant to a class of antibiotics called polymyxins, by plasmid-mediated resistance. Colistin is in the polymyxin class of antibiotics.
Professor Timothy Walsh, with the University of Cardiff, and a collaborator on the study, told BBC News “All the key players are now in place to make the post-antibiotic world a reality.
“If MCR-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.” Walsh added that if a patient became ill with an E. coli infection, there would be nothing we could do.
There have been reports of Colistin-resistant bacteria before, however, when antibiotic resistance did occur, it was only through mutation in a single organism. This latest discovery is much more worrisome because the mutation has arisen in a way that allows it to be easily shared with other bacteria. “The transfer rate of this resistance gene is ridiculously high, that doesn’t look good,” said Prof Mark Wilcox, from Leeds Teaching Hospitals NHS Trust.
During the study, scientists found the MCR-1 mutation had spread to E coli strain SHP45, Klebsiella pneumoniae strains, and Pseudomonas aeruginosa collected from five provinces between April 2011, and November 2014.
Tests on 1,322 blood samples from patients at two hospitals in Guangdong and Zhejiang provinces showed that 16 had the MCR-1 gene. The MCR-1 gene was also found in E coli collected from 78, or 15 percent of 523 samples of raw meat and 166 or 21 percent of 804 live animals.
The study concludes with a dire warning: “Although currently confined to China, MCR-1 is likely to emulate other global resistance mechanisms such as NDM-1. Our findings emphasize the urgent need for coordinated global action in the fight against pan-drug-resistant Gram-negative bacteria.
The NDM-1 gene was discovered in India in 2010 and has since spread around the world. Apart from polymixins and to a lesser extent tigecycline, all other antibiotics have proven to be ineffective against NDM-1 superbug.
One commentary in the lancet concludes the “implications [of this study] are enormous” and unless something significant changes, doctors would “face increasing numbers of patients for whom we will need to say, ‘Sorry, there is nothing I can do to cure your infection.'”
This study, “Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study” was published in the journal The Lancet infectious diseases, on November 18, 2015.
