Characterization of an IMP-4-Producing ST1873 Strain Recovered from an Infant with a Bloodstream Infection in China.

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 ST1873 strain, a rare sequence type (ST) isolated from an infant with a bloodstream infection in China.

PATIENTS AND METHODS

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

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 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 (pIMP-HZ1-like plasmid) but is smaller, lacking the quinolone resistance gene and multiple gene orthologs. Conjugation experiment revealed that pIMP-4-BKP19 is a non-conjugative plasmid. According to in silico MLST analysis, strain BKP19 belongs to a sporadic clone ST1873.

CONCLUSION

In summary, our study reports the first genome sequence of a ST1873 strain harbouring the class B β-lactamase 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.