Genomic comparison reveals natural occurrence of clinically relevant multidrugresistant extended-spectrum-β-lactamaseproducing Escherichia coli strains

Abstract

The effectiveness of antibiotics has been challenged by the increasing frequency of antimicrobial resistance (AMR), which has emerged as a major threat to global health. Despite its negative impact on the development of AMR, there are few effective strategies for reducing AMR in food-producing animals. Using wholegenome sequencing and comparative genomics of 36 multidrug-resistant (MDR) Escherichia coli strains isolated from beef cattle with no previous exposure to antibiotics, we obtained results suggesting that the occurrence of MDR E. coli also arises in animals with no antibiotic selective pressure. Extended-spectrum-β-lactamaseproducing E. coli strains with enhanced virulence capacities for toxin production and adherence have evolved, which implies important ramifications for animal and human health. Gene exchanges by conjugative plasmids and insertion elements have driven widespread antibiotic resistance in clinically relevant pathogens. Phylogenetic relatedness of E. coli strains from various geographic locations and hosts, such as animals, environmental sources, and humans, suggests that transmission of MDR E. coli strains occurs intercontinentally without host barriers.