Distribution of β-Lactamase Genes and Genetic Context of blaKPC-2 in Clinical Carbapenemase-Producing Klebsiella pneumoniae Isolates

Background: This study was 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 strains isolated from a teaching hospital of Wenzhou Medical University during 2015-2017. Polymerase chain reaction (PCR)-based amplification and whole-genome sequencing (WGS) were used to analyze the genetic context of the bla(KPC-2) gene. Conjugation experiments were performed to evaluate the transferability of bla(KPC-2)-bearing plasmids. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were performed to investigate the clonal relatedness of bla(KPC-2)-producing strains. Results: The bla(KPC-2) gene was identified from 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-beta-lactamases (ESBL5) and other antimicrobial resistance genes, were also found in KPC-positive K. pneumoniae (KPC-Kp) isolates. Mapping PCR and genomic sequencing revealed that the bla(KPC-2)-bearing sequence regions, which are 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. Conclusion: The bla(KPC-2) genes related to divergent mobile genetic elements encoded on transferable plasmids may transfer widely, facilitating the spread of carbapenem resistance among bacteria with different genetic backgrounds. The dissemination of bla(KPC)-bearing plasmids that collectively carry additional multidrug resistance genes has caused widespread public concern, further limiting the antibiotics available to treat infections caused by KPC-producing pathogens.