Whole genome assembly and functional portrait of hypervirulent extensively drug-resistant NDM-1 and KPC-2 co-producing Klebsiella pneumoniae of capsular serotype K2 and ST86

Objectives: To characterize an emergent carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) strain, NUHL30457, which co-produces NDM-1 and KPC-2 carbapenemases. Methods: We performed WGS analysis on a clinical carbapenemase-producing hypervirulent K. pneumoniae (CP-hvKP) strain NUHL30457. Sequence data were analysed using comparative genomics and phylogenetics. WGS was used to perform MLST, capsular genotyping and identification of virulence and antimicrobial resistance genes. The virulence of NUHL30457 was analysed by serumkilling assay, neutrophil phagocytosis and mouse lethality assay. Results: The NUHL30457 strain was carbapenem resistant and belonged to ST86 and serotype K2. A significant increase in resistance to serum killing and antiphagocytosis was found in the NUHL30457 strain compared with the reference strain. The murine lethality assay showed an LD50 of 2.5x10(2) cfu for the NUHL30457 strain, indicating hypervirulence. WGS revealed that NUHL30457 has a single 5.3Mb chromosome (57.53% G+C content) and four plasmids in the range 49.2-215.7 kb. The incompatibility group (Inc)N plasmid p30457-4 carried the bla(NDM-1) and qnrS1 genes. The IncFII(K) plasmid p30457-3 also carried an array of resistance elements, including bla(CTX-M-65), bla(TEM-1) and bla(KPC-2). The IncHI1/IncFIB plasmid p30457-1, which carried virulence genes, was identical to a pLVPK plasmid reported previously. Conclusions: To the best of our knowledge, this is the first report to isolate an ST86 hvKP strain that co-produces NDM-1 and KPC-2 carbapenemase. Further investigation is required to reinforce our understanding of the epidemiology and virulence mechanisms of this clinically significant CP-hvKP.