Characterisation of a multidrug-resistant hypervirulent ST367-KL1 Klebsiella quasipneumoniae subsp. similipneumoniae strain harbouring blaCTX-M-14 plasmid.

OBJECTIVES

To elucidate the characteristics of a multidrug-resistant hypervirulent Klebsiella quasipneumoniae subsp. similipneumoniae strain Kpn1587 isolated from a 77-year-old male patient's sputum with lung infection using whole-genome sequencing and various phenotypic assays.

METHODS

MIC of Kpn1587 was measured using the VITEK 2 system and broth microdilution method. String test, mucoviscosity assay, siderophore production assay, capsular polysaccharide extraction and quantification, cell assays and mouse systemic infection model were used to analyse the hypervirulent phenotype of the strain. The fitness of Kpn1587 was evaluated by growth curve and in vitro competition. A conjugation experiment was conducted to verify the transferability of the resistant plasmid. Elucidation of genomic features was carried out using whole-genome sequencing and comparative genomics.

RESULTS

Kpn1587 showed multiple antibiotic resistance and a high virulence phenotype with the resistant plasmid being able to transfer to an Escherichia coli recipient strain at a conjugative efficiency of 6.8 × 10-2 per donor. Genomic analysis revealed that the Kpn1587 strain belongs to the ST367-KL1 type, harbouring a repB-type virulence plasmid, pKpn1587-Vir, which carries typical virulence genes, and an IncFII resistance plasmid, pKpn1587-CTXM, which carries blaCTX-M-14.

CONCLUSIONS

Kpn1587 demonstrates, for the first time, the coexistence of an IncFII-type transferable plasmid carrying blaCTX-M-14 and a repB virulence plasmid in an ST367-KL1 type K. quasipneumoniae subsp. similipneumoniae strain. The co-occurrence of these plasmids underscores the potential for horizontal dissemination of this dual-threat phenotype, with important implications for clinical management and public health.