Genome Analysis of 6222 Bacterial Isolates from Livestock and Food Environments in Spain to Decipher the Antibiotic Resistome

<b>Background/Objectives:</b> Antimicrobial resistance (AMR) poses a significant threat to global health and the economy, with projected costs ranging from $300 billion to $1 trillion annually and an estimated 10 million deaths per year by 2050. The food chain, from primary production to retail, represents a critical entry point for antimicrobial resistant bacteria into communities. This underscores the need for a coordinated "One Health" approach, integrating efforts in animal production, environmental health, and human healthcare to address this global concern. This study aimed to characterize the global resistome in Spanish primary production by sequencing 6222 bacterial genomes from animal origin. <b>Methods and Results:</b> Whole genome sequencing was performed on bacterial isolates collected from various farms and analyzed using a validated bioinformatic pipeline. The analysis revealed a diverse range of bacterial species, with <i>Enterobacteriaceae</i> being the most prevalent family. <i>Escherichia coli</i> was the most common species, followed by <i>Salmonella enterica</i> and <i>Pseudomonas aeruginosa</i>. This study identified 1072 antimicrobial resistance genes coding for 43 different classes of resistance, potentially conferring resistance to 81 antimicrobials. Additionally, 79 different plasmid types were detected, highlighting the potential for horizontal gene transfer. <b>Conclusions:</b> The resistome analysis revealed genes conferring resistance to various antibiotic classes, as well as antiseptics, disinfectants, and efflux pump-mediated resistance. This comprehensive characterization of AMR genes circulating in bacteria from primary production provides crucial insights into the ecology of AMR in Spanish livestock.