Antibiotic resistance genes in companion animals and humans driven by the gut microbial communities: composition,...

The widespread and inappropriate use of antibiotics in both human and veterinary medicine has accelerated the emergence and dissemination of antibiotic resistance genes (ARGs) in various environments. Companion animals, due to their close and prolonged interactions with humans, have increasingly been recognized as potential reservoirs and transmitters of ARGs. However, the extent remains largely unclear to which companion animals influence the diversity and distribution of ARGs in humans. Understanding these interactions is essential for assessing environmental pathways of antibiotic resistance transmission and for developing effective mitigation strategies within the One Health framework. We examined the profiles of ARGs and gut microbial communities among three groups: companion animals, pet owners, and non-pet owners. Quantitative polymerase chain reaction (qPCR) assays were applied to determine the abundance and diversity of representative ARGs, while 16S rRNA gene sequencing was used to characterize the composition and structure of microbial communities. Comparative and correlation analyses were conducted to evaluate the relationships between ARG distribution patterns and microbial community profiles across different host groups.

Companion animals were found to possess the highest total abundance of ARGs (8.46 × 10¹⁰ copies/μL), while humans exhibited greater gut microbial diversity. ARGs ermB and tetQ displayed relatively high abundance in all three groups. In addition, intI-1 was significantly more abundant in pet owners than in non-pet owners. ARG profile of pet owners showed more similarity to that of their pets, assessed by the Jaccard similarity index. Age was associated with a limited subset of ARGs: sul2 and tetW decreased with age in companion animals, whereas aph(3'), cmlA, fexA and qnrS increased with age in humans. Notably, high correlation (r = -0.69/0.77) of oqxA-Megasphaera was identified, with negative correlation in animals and positive in pet owners, suggesting oqxA could be a potential key hub for ARGs dissemination.

Our findings show that pet owners exhibit similar ARG profiles to those in companion animals, suggesting pet ownership may drive convergence in profiles of ARGs. Moreover, these findings provides evidence of potential resistome overlap at the human-animal interface and highlight the need to incorporate companion animals into antimicrobial control programs under a One Health framework.