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Dogs may be passing antibiotic resistance to their owners

A new study has found that a dangerous gene responsible for antibiotic resistance can be passed from dogs to their owners. The mcr-1 gene has been found in healthy humans and their pet dogs.

The mcr-1 gene provides resistance to the antibiotic colistin, which is used as a last resort to treat drug resistant bacterial infections. The gene was first discovered in China, and has since been found in people and animals around the world. 

The research was led by Dr. Juliana Menezes, a PhD student in the Faculty of Veterinary Medicine at the University of Lisbon

“Colistin is used when all other antibiotics have failed – it is a crucial treatment of last resort. 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,” said Dr. Menezes.

The experts set out to investigate whether household pets may be acting as a reservoir of the mcr-1 gene and promoting the spread of antibiotic resistance. 

The study was designed to look for bacteria with resistance to colistin in healthy pet owners. The team analyzed fecal samples from 80 households, including 126 people and 102 cats and dogs.

Among the pets that were tested, 61 were healthy, 23 had skin and soft tissue infections (SSTI), and 18 had urinary tract infections (UTI).

The study revealed that eight dogs and four humans harbored bacteria with the mcr-1 gene. Three of the dogs were healthy, four had SSTIs, and one had a UTI. 

Upon further analysis, the researchers confirmed that the bacteria isolated from all 12 mcr-1 positive samples were resistant to multiple antibiotics.

In two of the households where dogs had skin and soft tissue infections, the mcr-1 gene was found in both dog and owner. Genetic testing showed that in one case, mcr-1 had clearly been transmitted between pet and owner.

While transmission in both directions is possible, it is thought that in this case the gene passed from dog to human, explained Dr. Menezes.

The findings raise concerns that pets can act as reservoirs of the dangerous gene, promoting the spread of bacterial resistance to last-resort antibiotics. The World Health Organization (WHO) classifies antibiotic resistance as one of the greatest public health threats facing humanity.

“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,” said Dr. Menezes. 

In separate research, experts have found that raw dog food is a major source of antibiotic-resistant bacteria, making it an “international public health risk.”

Both studies will be presented at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID).

By Chrissy Sexton, Staff Writer

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