Can Pets Harbor and Spread Antibiotic-Resistant Bacteria?

According to new research, pet dogs and cats are major contributors to the spread of antibiotic resistant bacteria.

This research will be presented at the ESCMID Global Congress (formerly ECCMID) in Barcelona, Spain, from April 27–30.

Concerns about pets acting as reservoirs of resistance and contributing to the spread of resistance to essential medications have been raised by the study’s discovery of evidence of multidrug-resistant bacteria being transferred between sick cats and dogs and their healthy owners in Portugal and the UK.

Globally, antibiotic resistance is rising to dangerously high levels. The World Health Organization (WHO) classified antibiotic resistance as one of the biggest public health threats facing humanity because it kills more than 1.2 million people annually worldwide and is expected to kill 10 million by 2050 if nothing is done.

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. 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.”

Juliana Menezes, Ph.D. Student, Study Lead Researcher and Faculty, Antibiotic Resistance Lab, Center of Interdisciplinary Research in Animal Health, Veterinary Medicine, University of Lisbon

Ms. Menezes and associates conducted tests on skin swabs, urine, and feces from dogs, cats, and their owners to check for Enterobacterales, a broad family of bacteria that includes Klebsiella pneumoniae and E. coli, that are resistant to common antibiotics.

The World Health Organization ranks third-generation cephalosporins, which are used to treat a variety of illnesses such as meningitis, pneumonia, and sepsis, as one of the most critically important antibiotics for human medicine, and carbapenems, which are used as a last resort when all other antibiotics have failed, as being resistant to these bacteria. In the prospective longitudinal study, participants included 22 dogs and 56 humans from 22 households in the UK and five cats, 38 dogs, and 78 humans from 43 households in Portugal.

All humans were in good health, while all pets suffered from either skin and soft tissue infections (SSTI) or urinary tract infections (UTI).

In Portugal, one dog (1/43 pets, 2.3%) was colonized by an OXA-181-producing multidrug-resistant Escherichia coli strain. OXA-181 is an enzyme that confers resistance to carbapenems.

Three cats and 21 dogs (24/43 pets, 55.8%) and 28 owners (28/78 owners, 35.9%) harbored ESBL/Amp-C producing Enterobacterales.  These are resistant to third-generation cephalosporins.

Both the pet and the owner of five homes - four of which had dogs and one with a cat - carried ESBL/AmpC-producing bacteria. The strains were identical, according to genetic analysis, suggesting that the bacteria were transferred from pet to owner.

A dog and its owner shared the same strain of antibiotic-resistant Klebsiella pneumoniae in one of these five households.

Two strains of multidrug-resistant Escherichia coli in the United Kingdom that produce NDM-5 beta-lactamase colonized one dog (1/22 pets, 14.3%). These E. Coli were resistant to carbapenems, third-generation cephalosporins, and several other antibiotic families.

Three proprietors (3/24 owners, 12.5%) and eight dogs (8/22 pets, 36.4%) both had ESBL/AmpC-producing Enterobacterales isolated from them.

The dog and owner in two homes carried the same ESBL/AmpC-producing bacteria. 

Although the direction of transmission could not be established, the timing of the positive ESBL/AmpC-producing bacterial tests in three of the Portuguese homes strongly suggests that in these cases at least, the bacteria were being transferred from pets (two dogs and one cat) to humans.

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

Juliana Menezes, Ph.D. Student, Study Lead Researcher and Faculty, Antibiotic Resistance Lab, Center of Interdisciplinary Research in Animal Health, Veterinary Medicine, University of Lisbon

Pets and people can spread bacteria by handling excrement and by petting, touching, or kissing each other.  To prevent transmission, the researchers advise owners to practice good hygiene, such as washing their hands after handling their waste and after petting their dog or cat.

When your pet is unwell, consider isolating them in one room to prevent the spread of bacteria throughout the house and clean the other rooms thoroughly.”

Juliana Menezes, Ph.D. Student, Study Lead Researcher and Faculty, Antibiotic Resistance Lab, Center of Interdisciplinary Research in Animal Health, Veterinary Medicine, University of Lisbon

All of the cats and dogs were effectively treated for infections. Since the owners were free of infections, they did not require medical attention.