Cats and dogs could be passing on superbugs to their owners

Healthy cats and dogs could be passing on superbugs to their owners, research suggests.

A study of 2,800 hospital patients suggests pets could be passing on drug resistant organisms.

Overall, around 30 per cent of hospital patients tested positive for such bugs.

All 626 pet owners were asked to send back samples from their pets.

Of these, 15 per cent of dogs and five per cent of cats tested positive for one superbug.

In four of the cases, the bugs were the same species and showing the same antibiotic resistance in pets and owners.

Whole genome sequencing only identified one pair as genetically identical in a dog and an owner, with the matching pathogen identified as a type of E coli.

Observational study

Scientists presenting the research at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) in Copenhagen, Denmark, said the findings suggest that multi-drug resistant organisms can be passed on from pets.

However, they stressed that the study was observational - meaning it could not prove the bugs were being spread from one species to another, nor that the infection did not start with the patients.

The fact that only a handful of cases were identified suggests neither cat nor dog ownership is an important risk factor for causing the spread of infection among their owners, they said.

The study of over 2,800 hospital patients and their companion animals is by Dr Carolin Hackmann from Charité University Hospital Berlin, Germany, and colleagues.

“Our findings verify that the sharing of multidrug-resistant organisms (MDROs) between companion animals and their owners is possible,” says Dr Hackmann.

“However, we identified only a handful of cases suggesting that neither cat nor dog ownership is an important risk factor for multidrug-resistant organism colonisation in hospital patients.”

Pets as reservoirs of MDROs a growing concern

The role of pets as potential reservoirs of MDROs is a growing concern worldwide.

Antimicrobial resistance happens when infection-causing microbes (such as bacteria, viruses or fungi) evolve to become resistant to the drug designed to kill them.

Estimates suggest that antimicrobial resistant infections caused almost 1.3 million deaths and were associated with nearly five million deaths around the world in 2019.

In the study, researchers wanted to find out whether cats and dogs play a role in the infection of hospital patients with MDROs.

They focused on the most common superbugs in hospital patients. These include methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), 3rd generation cephalosporin-resistant Enterobacterales (3GCRE) and carbapenem-resistant Enterobacterales (CRE), which are resistant to multiple antibiotics including penicillin and cephalosporins.

Between June 2019 and September 2022, nasal and rectal swabs were collected from 2,891 patients hospitalised in Charité University Hospital Berlin (1,184 patients with previous colonisation or colonisation on admission and 1,707 newly admitted patients as controls), and from any dogs and cats that lived in their households.

Genetic sequencing was used to identify both the species of bacteria in each sample, and the presence of drug resistance genes. Whole genome sequencing was used to confirm the possible sharing of resistant bacteria.

Dr Hackmann said: “Although the level of sharing between hospital patients and their pets in our study is very low, carriers can shed bacteria into their environment for months, and they can be a source of infection for other more vulnerable people in hospital such as those with a weak immune system and the very young or old.”

The authors also highlighted some limitations to the study, such as problems taking swab samples from pets.