Distribution of β-lactamase Gene and Genetic Context of blaKPC-2 in Clinical Carbapenemase-producing Klebsiella Pneumoniae Isolates

Background: This study is designed to characterize the dissemination mechanism and genetic context of Klebsiella pneumoniae carbapenemase (KPC) genes in carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates.Methods: A retrospective analysis was performed on CRKP isolates from a teaching hospital of Wenzhou Medical University from 2015-2017. Polymerase chain reaction (PCR)-based amplification and whole-genome sequencing (WGS) were used to analyze the genetic context of the blaKPC-2 gene. Conjugation experiments were performed to evaluate the transferability of blaKPC-2-bearing plasmids. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were performed to investigate the clonal relatedness of blaKPC-2-producing strains.Results: The blaKPC-2 gene was identified in 13.61% (40/294) of clinical K. pneumoniae isolates. Three different sequence types (ST11, ST15 and ST656) and 5 PFGE subtypes (A to E) were classified among them. ST11 was the dominant sequence type (92.50%, 37/40). Plasmid-oriented antibiotic resistance genes such as extended spectrum-β-lactamases (ESBLs) and other antimicrobial resistance genes were also found in KPC-positive K. pneumoniae (KPC-Kp). Mapping PCR and genomic sequencing revealed that the blaKPC-2-bearing sequence regions related to different mobile elements, including Tn1721- and IS26-based transposons, were mainly located in but not restricted to IncFII-like plasmids and were structurally divergent.Conclusions: The blaKPC-2 genes related to divergent mobile genetic elements encoded on transferable plasmids may transfer easily and widely, resulting in the spread of resistance among bacteria of different species or genera. Co-infection of KPC-Kp plasmids carrying additional non-β-lactam antibiotic resistance genes simultaneously further limits the antibiotics available to treat infections with KPC-producing pathogens.