Introduction: Carbapenem-Resistant Enterobacteriaceae (CRE) has posed a significant threat to humans.The aim of this study was to investigate the molecular characteristics of bla_KPC-producing Escherichia coli in a university-affiliated tertiary hospital.
Methods: Polymerase chain reaction (PCR) and BLAST+ software were used to detect the prevalence of bla_KPC in E. coli and Klebsiella pneumoniae. Whole-genome sequencing was performed for the bla_KPC-harboring clinical E. coli isolates. Antimicrobial resistance genes, MLSTs, KPC-carrying plasmid typing and genetic environment of bla_KPC were analyzed. A maximum likelihood core single nucleotide polymorphism (SNP)-based phylogeny tree was constructed to determine the evolutionary relationships within this ST131 collection. Conjugation experiments were performed to determine the mobilization of bla_KPC. The minimal inhibitory concentrations of the common antimicrobial agents were determined using the broth microdilution method.
Results: The prevalence of bla_KPC in 424 clinical E. coli isolates and 1636 E. coli strains from GenBank database were 2.2% (45/2060) whereas the detection rate of bla_KPC in K. pneumoniae from the GenBank database was 29.8% (415/1394). The bla_KPC-harboring conjugants exhibited resistance to multiple β-lactams, except for cefepime-zidebactam and ceftazidime-avibactam. All bla_KPC-carring E. coli isolates were susceptible to tigecycline and polymyxin B. ST131 was the dominant sequence type of bla_KPC-carring E. coli, accounting for 40.0% (18/45). Most of the bla_KPC-producing ST131 E. coli (89.5%,17/19) belonged to clade C ST131 lineage. Genetic environment analysis revealed that 57.8% (26/45) of bla_KPC gene was linked to Tn 4401-associated structure ISKpn6-bla_KPC-ISKpn7. IncN was the most common plasmid type in KPC-producing E. coli whereas IncFII was the dominant plasmid type in KPC-producing K. pneumoniae.
Conclusion: The detection rate of bla_KPC was lower in E. coli compared with K. pneumoniae. The dominant sequence and plasmid types of bla_KPC-harboring isolates differed between E. coli and K. pneumoniae. Further studies about the role of the defense system in acquisition of KPC-plasmids in E. coli will be performed to provide new insights into the low prevalence of bla_KPC.

Keywords: Escherichia coli, bla_KPC, carbapenemases, plasmids typing