Potential human health risk of carbapenem-non-susceptible Pseudomonas aeruginosa from companion animals.

BACKGROUND AND

OBJECTIVES

The close bond between companion animals and humans may accelerate the spread of antimicrobial-resistant bacteria. Pseudomonas aeruginosa, an opportunistic pathogen in both, poses a public health threat due to antimicrobial resistance (AMR) and diverse virulence factors. However, One Health-based comparison remains limited. This study investigated the current AMR status and molecular characteristics of P. aeruginosa in companion animals in Japan to assess potential human health risks.

METHODS

We examined 197 P. aeruginosa clinical isolates from companion animals [dogs (n = 99) and cats (n = 98)] across Japan in 2024. Antimicrobial susceptibility to human clinical antibiotics was evaluated. In carbapenem-non-susceptible isolates, multilocus sequence typing and detection of resistance genes and virulence factors were performed.

RESULTS

Ciprofloxacin (20.3%) and piperacillin (10.7%) showed the highest resistance rates, with 5.6% of isolates being multidrug-resistant. Carbapenem resistance rates were 6.1% for imipenem and 1.0% for meropenem. Thirty-five isolates (17.8%) exhibited carbapenem non-susceptibility but remained susceptible to cefepime, ciprofloxacin, or amikacin. Of 27 identified sequence types, 20 (77.1% of carbapenem-non-susceptible isolates) were known in humans, including two high-risk clones (ST233 and ST298; 8.6%) reported for the first time in Japanese companion animals. These isolates carried mutations in efflux pump-related genes and multiple virulence factors. One showed close genetic relatedness to a human isolate, suggesting possible interspecies transmission.

CONCLUSIONS

Our findings highlight the potential cross-species transmission risk of antimicrobial-resistant P. aeruginosa. Identification of shared high-risk clones with multiple virulence factors emphasizes the need for continuous vigilance and actions within the One Health framework.