Adam Dr. Kerek ^1,2* Emese Szabo ² Abel Szabo ² Marton Papp ^1,3 Krisztian Banyai ^1,2,4 Gabor Kardos ^1,5,6,7 Eszter Kaszab ^1,5,8 Krisztina Bali ^1,8 Akos Jerzsele ^1,2

• ¹ National Laboratory of Infectious Animal Diseases, Antimicrobial Resistance, Veterinary Public 7 Health and Food Chain Safety, University of Veterinary Medicine Budapest, budapest, Hungary
• ² Department of Pharmacology and Toxicology, University of Veterinary Medicine, Budapest, Hungary
• ³ Centre for Bioinformatics, University of Veterinary Medicine, Budapest, Hungary
• ⁴ HUN-REN Veterinary Medical Research Institute, Budapest, Hungary
• ⁵ Institute of Health Sciences, Faculty of Health, University of Debrecen, Debrecen, Hungary
• ⁶ National Public Health Institute (OKI), Budapest, Hungary
• ⁷ Department of Metagenomics, University of Debrecen, Debrecen, Hungary
• ⁸ Department of Microbiology and Infectious Diseases, University of Veterinary Medicine Budapest, Budapest, Hungary

Introduction: One of the greatest challenges of our time is antimicrobial resistance, which could become the leading cause of death globally within a few decades. In the context of One Health, it is in the common interest to mitigate the global spread of antimicrobial resistance by seeking alternative solutions, alongside appropriate drug selection and responsible use. Probiotics offer a potential avenue to reduce antibiotic usage; however, there is a scarcity of research that examines commercial products in terms of carrying antimicrobial resistance genes (ARGs) involved in resistance development through microbial vectors.Methods: Our study investigated ten commercially available probiotic products for cats and dogs. Initially, we conducted phenotypic testing through determination of minimum inhibitory concentration (MIC) for antibiotics important in animal and public health. Subsequently, we performed next- generation sequencing (NGS) of the products to elucidate the genetic background behind the decrease in phenotypic sensitivity.In total, 19 types of ARGs were identified, with 57.9% being found on plasmids, and in two cases, carriage as mobile genetic elements were found. One of the genes identified was the APH(3')-Ia gene, capable of inactivating aminoglycoside antibiotics through phosphotransferase enzyme production regulation, while the other was the tetS gene, capable of conferring reduced sensitivity to tetracycline antibiotics through target protection.Discussion: Our findings underscore the importance of approaching antimicrobial resistance investigations from a broader perspective. We suggest that further studies in this area are justified and raise questions regarding the need to extend legally required studies on probiotic products from their use in economic livestock to their use in companion animals.