Molecular characteristics of CTX-M β-lactamase-producing and quinolone-resistant Escherichia coli among deer in a popular tourist spot in Japan

Introduction: Antimicrobial resistance (AMR) is a growing global concern. Clonal lineages of CTX-M β-lactamase-producing Escherichia coli (CTXE) and quinolone-resistant E. coli (QREC) were disseminated among deer population in a famous tourist destination (Nara Park; NP) in Japan. Hypothesis or gap statement: The molecular characteristics of CTXE or QREC isolates which could pose a threat to public health has not been elucidated. Aim: This study aimed to characterize the genetic traits of CTXE and QREC isolates derived from NP deer and compare them with lineages prevalent worldwide. Methodology: Sixteen CTXE and three QREC isolates recovered from NP deer feces between 2018 and 2020 were analyzed using whole-genome sequencing. For endemic lineages, phylogenetic trees were constructed against the isolates registered in EnteroBase database using the core genome single nucleotide polymorphism scheme. Results: The most prevalent lineage in NP deer was ST3580. Several pandemic lineages, such as sequence type (ST) 38, ST58, and ST117, were included. The QREC lineages prevalent among deer were designated as extra-intestinal pathogenic E. coli or uropathogenic E. coli. Thirteen of the 24 antimicrobial resistance genes (ARGs) were considered high-risk ARG families. Chromosomal integration of blaCTX-M-15 was observed in all plasmid-negative isolates. Phylogenetic analysis suggested relationships between NP isolates and isolates sourced from environment or poultry. Conclusion: ST3580 has high potential to disseminate clonally. Furthermore, multiple clinically relevant lineages of CTXE and QREC are endemic in NP deer; however, they could be less virulent than isolates belonging to the same lineages which could cause severe infectious diseases. Further studies are required to investigate the relationship between chromosomal integration of plasmid-encoded genes and the stable propagation of AMR bacteria in wildlife and the environment.