Alarm bells have been sounded after a woman in the U.S. was detected >with bacteria resistant to a last-resort antibiotic . The 49-year-old was carrying E. coli bearing a new gene, mcr-1, which is resistant to even colistin, the last available antibiotic that works against strains that have acquired protection against all other medication. This is the first reported case of the mcr-1 gene in an E. coli strain found in a person living in America, but it raises worries about how far it may have spread. The results of mcr-1 gene identification were published recently in the journal Antimicrobial Agents and Chemotherapy . Though resistance to colistin has been detected for about 10 years in several countries, the danger from this has been somewhat played down since such resistance was brought about by gene mutations that cannot spread easily between bacteria. But mcr-1 poses a threat of an entirely different order; in this case a small piece of DNA (plasmid) found outside the chromosome carries a gene responsible for antibiotic resistance. Since the gene is found outside the chromosome, it can spread easily among different types of bacteria, as well as among patients. In the case of E.coli , the colistin resistance is not insurmountable as it is still treatable by other known drugs. But were the gene to spread to bugs treatable by only last-resort antibiotics, we could be facing the dreaded — and indeed, long-anticipated — superbug. Thus, the discovery of mcr-1 in more countries and settings increases the chances of the emergence and spread of resistance against all available antibiotics. It could well lead to an era without effective drugs to treat bacterial infections — the post-antibiotic age, as it were.
The mcr-1 gene was first identified in China in November 2015, following which there were similar reports from Europe and Canada. The unchecked use of antibiotics in livestock is a major reason for the development of drug resistance. Indeed, given the widespread use of colistin in animals, the connection to the drug-resistant mcr-1 gene appears quite clear. A November 2015 paper in The Lancet noted that a significantly higher proportion of mcr-1 positive samples was found in animals compared with humans, suggesting that the mcr-1 gene had emerged in animals before spreading to humans. Besides being administered for veterinary purposes, colistin is used in agriculture. The global community needs to urgently address the indiscriminate use of antibiotics in an actionable manner, and fast-track research on the next generation of drugs.