Mcr-1: the potentially untreatable superbug being passed from dogs to owners

Dogs are infecting their owners with a superbug that could become resistance to last-resort antibiotic colistin, new research suggests.

The Telegraph reports that scientists are warning of a potential “nightmare scenario” after discovering that the mcr-1 gene can be passed on to humans by “sharing beds with dogs”. The gene “is harboured in the gut and transported via microscopic fecal particles, also making dog baskets an area of increased risk”, says the newspaper.

Reseachers at the University of Lisbon took faecal samples from 126 healthy people from a total of 80 households who between them lived with 102 cats and dogs. Over a period of two years up to February 2020, eight dogs and four people were found to be carrying mcr-1.

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And in two households, the mcr-1 gene was found in both the dog and the owner, according to the scientists, who presented their findings at the European Congress of Clinical Microbiology and Infectious Diseases online conference this weekend.

First reported in China in 2015, the gene “confers resistance to colistin, an antibiotic of last resort used to treat infections from some bacteria resistant to all other antibiotics”, says Medical Xpress. “The nightmare scenario that could emerge is mcr-1 combining with already drug-resistant bacteria to create a truly untreatable infection,” the health news site continues.

Experts have been warning for years that the overuse of colistin, especially on meat-farmed animals, “risks the rise of mutant genes” that could make the drug “useless in humans”, The Telegraph reports.

“Colistin is used when all other antibiotics have failed, it is a crucial treatment of last resort,” said Dr Juliana Menezes, who led the research. “If bacteria resistant to all drugs acquire this resistance gene, they would become untreatable, and that’s a scenario we must avoid at all costs.

“We know that the overuse of antibiotics drives resistance and it is vital that they are used responsibly, not just in medicine but also in veterinary medicine and in farming.”

The use of antibiotics in farming is believed to be fuelling a “growing crisis of antimicrobial resistance” that is estimated to kill 700,000 people a year globally - and that “is forecast to kill ten million a year by 2050 if left unchecked”, says The Telegraph.

The World Health Organization has described antibiotic resistance as “one of the biggest threats to global health, food security, and development today”.

In a bid to tackle the growing problem, the EU is banning the “routine preventive” use of antibiotics in farm animals from next year, as the Financial Times reported earlier this year. China has prohibited the use of Colistin in animal feed since 2017, and the US has also introduced regulations aimed at cutting antibiotic use.