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

Abstract

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.