Purpose: This study retrospectively analyzed the genome characteristics of blaKPC-2  in multidrug-resistant Klebsiella pneumoniae  collected from the ICU of a teaching hospital in Shanghai, China.
Methods: From February 2018 to December 2019, 36 strains of multidrug-resistant Klebsiella pneumoniae  were collected from the bronchoalveolar lavage fluid of critically ill patients. The genome of all isolates was obtained through the Illumina sequence, and single nucleotide polymorphisms of the blaKPC-2  gene were analyzed to explore blaKPC-2 ’s evolutionary characteristics. Different strains’ genetic relationships and homology were studied by constructing an evolutionary tree on a single copy orthologue. Pacbio combined Illumina sequence was conducted to evaluate the structure and potential mobility of drug-resistant plasmids of the strain KP-s26.
Results: The distribution of resistance and virulence genes had little difference, but most strains had significant differences in the plasmid-encoded region. Most strains (31/36) carried the carbapenemase gene blaKPC-2 , with no single nucleotide polymorphism in different strains. Extended-spectrum β-lactamase resistance genes, such as blaCTX-M  and blaSHV , were found in the isolates, but no metallo-β-lactamases were detected. All strains with blaKPC-2  coexisted with chromosomal-associated fosfomycin resistance genes fosA6 , and the coexistence of blaKPC-2  and blaCTX  variants (blaCTX -M-15, blaCTX -M-65, and blaCTX -M-27) was also detected in 29/31 strains. The isolate KP-s26 carried five circular plasmids. pA and pB were conjugate plasmids, as they carried drug resistance genes and contained a complete IV secretion system.
Conclusion: The blaKPC-2  carbapenemase gene is relatively conservative in the process of evolution; drug-resistant plasmids containing conjugated transfer elements contribute to the spreading of drug resistance. The coexistence of blaKPC-2  with fosA6  or blaCTX-M  variants was associated with increased fosfomycin resistance and broad-spectrum β-lactam resistance, respectively.
Clinical Trials Registration: Clinical Trials.gov Identifier: NCT03950544
Keywords: Klebsiella pneumoniae , blaKPC-2 , whole-genome sequencing, single nucleotide polymorphism, drug-resistant plasmids