Purpose: Imipenemase (IMP), an Ambler class B metallo-β-lactamase, is an important carbapenemase that confers resistance to almost all β-lactams. In this study, we characterized the genomic feature of an IMP-4-producing Klebsiella pneumoniae ST1873 strain, a rare sequence type (ST) isolated from an infant with a bloodstream infection in China.
Patients and Methods: K. pneumoniae  strain, BKP19, was collected from a bloodstream infection in an infant who was hospitalized at the department of paediatrics. The whole genome sequence of the strain was sequenced using the Illumina NovaSeq 6000 platform and long-read MinION sequencer. Multilocus sequence typing, antimicrobial resistance gene identification, plasmid and phylogenetic relationship analysis of the strain were analysed by various bioinformatics approaches.
Results: K. pneumoniae  BKP19 was resistant to multiple antimicrobials, including carbapenems. Eleven antimicrobial resistance genes corresponding to beta-lactam resistance, quinolone resistance, phenicol resistance and fosfomycin resistance could be identified in the genome. The carbapenem resistance gene bla _IMP-4 was located in an IS26-associated class 1 integron of an IncN-type plasmid with 39,033 bp (pIMP-4-BKP19). Sequence alignment revealed that pIMP-4-BKP19 is closely related to the common plasmid carrying IMP-4 in K. pneumoniae  (pIMP-HZ1-like plasmid) but is smaller, lacking the quinolone resistance gene qnrS1  and multiple tra  gene orthologs. Conjugation experiment revealed that pIMP-4-BKP19 is a non-conjugative plasmid. According to in silico MLST analysis, K. pneumoniae  strain BKP19 belongs to a sporadic clone ST1873.
Conclusion: In summary, our study reports the first genome sequence of a K. pneumoniae  ST1873 strain harbouring the class B β-lactamase bla _IMP-4 in an IncN-type plasmid recovered from an infant with a bloodstream infection in China. Considering the global emergence of IMP-4 carbapenemase, more attention must be paid to prevent its future prevalence.
Keywords: Klebsiella pneumoniae , bla _IMP-4, IncN plasmid, ST1873, bloodstream infection