Occurrence and genomic characterization of ESBL-producing Escherichia coli ST29 strains from swine with abundant virulence genes

Food-production animals were considered to be a major reservoir of antimicrobial-resistant bacteria and clinically relevant pathogens. The potential of commensal Escherichia coli from pigs as a source of opportunistic pathogens associated with extraintestinal infections in humans needs to be assessed. In this study, 13 E. coli isolates from an intensive pig farm in China were analyzed using whole genome sequencing followed by in-depth in silico analysis. Genomic analysis showed comprehensive antimicrobial resistance profiles, with each isolate carrying between 4 and 22 antimicrobial resistance genes. Although these E. coli isolates were assigned to low virulence phylogroup A and B1, 31 different virulence genes were detected at least once in the 13 sequenced isolates. Extraintestinal pathogenic E. coli-associated virulence genes, including iss, iha, tsh and iroN, were found in commensal E. coli isolates in this study. Of note, a large number of virulence genes (n = 22) were identified in ESBL-producing E. coli sequence type (ST) 29 isolates. Our study revealed the presence of comprehensive antimicrobial resistance and virulence gene profiles in commensal E. coli isolates of pigs. The emerged ESBLproducing E. coli ST 29 isolates harboring a high abundance of VAGs highlighted that this new clonal linage may pose a threat to public health.