Pandemic spread of blaKPC-2 among Klebsiella pneumoniae ST11 in China is associated with horizontal transfer mediated by IncFII-like plasmids.

Objective: The aim of this study was to investigate the spread of the blaKPC-2 gene among Klebsiella pneumoniae and to illustrate the mechanism of dissemination of K. pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) ST11 in China.

Methods: A total of 354 K. pneumoniae isolates were collected from four hospitals in China and were characterized by multilocus sequence typing (MLST). Mobile genetic elements (MGEs) and pulsed-field gel electrophoresis (PFGE) analysis were used to identify the subtypes of K. pneumoniae ST11. Polymerase chain reaction (PCR)-based amplification and sequencing were performed to analyse Tn1721 transposons and IncFII-like plasmids. Electroporation experiments and whole-genome sequencing (WGS) were used to reveal the genetic environment of the blaKPC-2 gene.

Results: As the primary type (87.1%) of KPC-Kp, K. pneumoniae ST11 was not predominant in non-KPC-Kp (3.1%). ST11 KPC-Kp was clonally heterogeneous and could be further classified into 11 MGE types and 14 PFGE subtypes. Five Tn1721-blaKPC-2 variants were identified on IncFII-like plasmids. The detection rate of IncFII-like plasmids was much higher in ST11 KPC-Kp (100%) compared with non-ST11 KPC-Kp (16.0%) and the non-KPC-Kp group (7.5%). Moreover, the IncFII plasmid (with IIa replicon) was primarily detected on the MGE-F type (61.7%). The IncFIIk plasmid (with IIk replicon) was clustered into two subtypes: MGE-A (28.3%) and -F (41.5%). The detection of the IncFII and IncFIIk plasmids on MGE-A was 57.1% (20/35) and 42.9% (15/35), respectively.

Conclusions: A close correlation was shown between ST11 KPC-Kp and IncFII-like plasmids. Horizontal transfer mediated by IncFII-like plasmids plays an important role in the pandemic expansion of blaKPC-2 among K. pneumoniae ST11 in China.