A study has ranked the antimicrobial-resistant organisms considered most important at the human–companion animal interface

A Tennessee study place methicillin-resistant Staphylococcus aureus (MRSA) first and ESBL-producing Escherichia coli second.

The exercise highlights dogs and cats as part of household AMR transmission networks and proposes a practical state-level agenda built around surveillance, laboratory capacity and veterinary antimicrobial stewardship.

Seven AMR threats ranked

The final ranking placed MRSA first, followed by ESBL-producing E. coli and multidrug-resistant Pseudomonas aeruginosa. The remaining priorities, in descending order, were extensively drug-resistant Campylobacter jejuni, carbapenemase-producing Enterobacterales, multidrug-resistant nontyphoidal Salmonella and vancomycin-resistant Enterococcus.

Why dogs and cats matter

Companion animals occupy a distinctive One Health position because they share homes, furniture and close physical contact with people, including children, older adults and immunocompromised household members. Resistant bacteria can colonize skin or the gastrointestinal tract without causing disease and still participate in transmission between people, animals and their environment. The study points to evidence of bidirectional transmission between humans and pets. MRSA strains indistinguishable between owners and dogs have been documented, while ESBL-producing E. coli has been found globally in dogs and cats and may circulate within households. The authors nevertheless caution that companion animals should not be interpreted as the dominant source of AMR; they are one component of a more complex transmission network.

Surveillance remains less developed than in human medicine

That uncertainty is partly a surveillance problem. The authors note that AMR monitoring in companion animals is considerably less standardised than in human healthcare or food-animal systems. This makes it difficult to estimate the true prevalence of resistant organisms in dogs and cats, identify emerging resistance patterns or determine the direction of transmission within households.

The Tennessee exercise was therefore designed not simply to produce a ranking, but to decide where limited public-health and veterinary resources could be directed first.

From ranking to an operational plan

Workshop participants proposed several concrete next steps: establishing an integrated Tennessee AMR working group, developing sentinel surveillance, creating a statewide veterinary antibiogram, mapping laboratories capable of confirmatory testing, strengthening veterinary workforce and stewardship partnerships, and preparing targeted risk-communication materials.

A veterinary antibiogram could be particularly useful because it would summarise local antimicrobial susceptibility patterns and help veterinarians make more evidence-based treatment choices instead of relying on broader national data.

A model that could be used beyond Tennessee

The study is small and does not measure prevalence directly. It is a prioritisation exercise based on published evidence and expert judgement, not a population-wide surveillance survey. The ranking may therefore differ in another state or country with different veterinary practices, resistance profiles or laboratory capacity.

Its value lies in providing a reproducible way to move from a broad AMR problem to a short list of organism–resistance combinations linked to concrete surveillance and preparedness actions.

In the United States, where CDC estimates more than 2.8 million antimicrobial-resistant infections and over 35,000 associated deaths each year, applying this approach to companion animals addresses a part of the One Health interface that remains much less structured than hospital or livestock surveillance.