Drug-resistant bacteria has emerged as one of the biggest health problems of this century. The fact that some pathogens can adapt to all our medicine and become virtually untreatable is absolutely terrifying. For instance, there’s already a strain of gonorrhea that’s essentially untreatable, and drug-resistant pathogens kill over one million people a year.

The scale of the problem is not entirely clear, and it’s not in just humans either. Animals on farms can also harbor drug-resistant bacteria. In addition to all of this, there may be a new problem. In a recent study, researchers found that these “superbugs” are being passed from pets to their owners. Although this isn’t necessarily making the humans sick, this suggests that pets may also play a role in the health crisis.

Our best friends and microbes

If you have a dog or a cat, you probably have a lot of physical contact. Let’s be honest — the petting, the kissing, the sharing a room (and often, a bed) — we all love to snuggle our little munchkins. We don’t usually think about germs when we do this, but germs can be transmitted in this process — in both directions.

In the new research, an international team investigated 43 households in Portugal (5 cats, 38 dogs, 78 humans) and 22 households in England (22 dogs and 56 humans), finding that pets can serve as a reservoir for superbugs.

All of the humans were healthy. Even if their pets transmitted drug-resistant bacteria, this didn’t seem to make them sick. Remarkably, however, all of the pets had at least one infection (whether skin, soft tissue, or urinary tract).

The researchers collected urine and fecal samples from the pets, as well as skin swabs. They focused on Enterobacterales (a large family of bacteria that includes E. coli) that were resistant to third-generation cephalosporins. These are some of the most critical antibiotics for humans, treating a broad range of conditions, from sepsis to meningitis. The team also looked at bacteria resistant to carbapenems — often considered the last line of antibiotic defense used when other antibiotics fail.

In Portugal, 3 cats and 21 dogs harbored bacteria resistant to cephalosporins, and one dog also had bacteria resistant to carbapenems. Furthermore, in five households, both the pets and the owners had the same bacteria, a sign that the pathogens passed from one to the other. The dog that had bacteria resistant to carbapenems was also among this group.

Meanwhile, in the UK, one dog carried bacteria resistant to both classes of antibiotics, and two households showed signs of bacteria passing between pets and humans.

Addressing AMR bacteria transmission

“Recent research indicates that the transmission of antimicrobial resistance (AMR) bacteria between humans and animals, including pets, is crucial in maintaining resistance levels, challenging the traditional belief that humans are the main carriers of AMR bacteria in the community,” says lead researcher Juliana Menezes, of the Antibiotic Resistance Lab at the Centre of Interdisciplinary Research in Animal Health, Faculty of Veterinary Medicine, University of Lisbon.

“Understanding and addressing the transmission of AMR bacteria from pets to humans is essential for effectively combating antimicrobial resistance in both human and animal populations.”

It’s not 100% clear whether the pets passed the bacteria to humans or the other way around. But, given that the pets were sick and the humans were not, the former seems more likely. The researchers suggest that if your pet has such bacteria, you should clean your house very thoroughly and consider taking measures to reduce the risk of transmission.

But perhaps the most important finding is that our pets can be reservoirs for these bacteria. This is particularly true if they go outside. Even if they are not making us sick, this may be contributing to general drug-resistance.

“Our findings underline the importance of including pet-owning households in national programs that monitor levels of antibiotic resistance,” Menezes said in a meeting news release. “Learning more about the resistance in pets would aid in the development of informed and targeted interventions to safeguard both animal and human health.”

All the pets were successfully treated of their infections. The owners did not require any treatment.

The research will be presented at the ESCMID Global Congress in Barcelona, Spain, from April 27 to April 30