Characterization of a tmexCD1-toprJ1-positive multidrug-resistant Klebsiella pneumoniae isolate in a chicken farm

Plasmid-mediated tmexCD1-toprJ1 in multidrug-resistant Klebsiella pneumoniae represent an emerging challenge due to their ability to confer tigecycline resistance and disseminate through mobile genetic elements. Understanding the genomic context and transmission potential of tmexCD1-toprJ1 -carrying strains in animal production environments is important for assessing their risk at the animal–environment–human interface. In 2020, a tigecycline-resistant Klebsiella pneumoniae strain, AH20CEAE23, was isolated from drinking water used for poultry production at a chicken farm in Anhui province, China. Antimicrobial susceptibility testing, conjugation assays, plasmid stability analysis, and whole-genome sequencing using Illumina HiSeq and Nanopore platforms were performed to characterize its resistance profile, transferability, and genomic features. The K. pneumoniae strain AH20CEAE23 exhibited resistance to 13 commonly used antibiotics and carried 26 resistance genes, including bla CTX−M−27 and bla DHA−1 . The MLST sequence type of the strain was ST11, and the tmexCD1 - toprJ1 gene cluster was located on an IncFIA-IncFIB-IncHI1B hybrid plasmid, designated pYUAHCE23. Comparative genomic analysis revealed that pYUAHCE23 contained multiple IS 26 elements and showed high similarity to previously reported plasmids from chicken-derived K. pneumoniae strains in China. The plasmid was successfully conjugatively transferred to Escherichia coli C600 and K. pneumoniae HZ7H108, and it remained stable in K. pneumoniae without selective pressure. The genomic characterization of a poultry farm-associated ST11 K. pneumoniae strain revealed an IS 26 -rich IncFIA-IncFIB-IncHI1B hybrid plasmid carrying tmexCD1 - toprJ1 and multiple resistance determinants. The transferability of this plasmid highlights the potential for dissemination of plasmid-mediated tigecycline resistance and the importance of monitoring mobile resistance platforms in agricultural settings.