Characterisation of a Novel Hybrid IncFII:IncR:IncN Plasmid Co-Harboring and from a Clinical ST11 Carbapenem-Resistant Strain.

Purpose: We aimed to characterize a novel and co-carrying hybrid plasmid from a clinical carbapenem-resistant  (CRKP) strain.

Methods: Antimicrobial susceptibility was determined by the broth microdilution method. Plasmid size and localization were estimated using S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and Southern blotting. Plasmid transfer ability was evaluated by conjugation experiments. Whole genome sequencing (WGS) was performed using Illumina NovaSeq6000 and Oxford Nanopore MinION platforms. Genomic characteristics were analyzed using bioinformatics methods.

Results: Strain ZY27320 was a multidrug-resistant (MDR) clinical ST11 strain that confers high-level resistance to carbapenems (meropenem, MIC 128 mg/L; imipenem, MIC 64 mg/L) and ceftazidime/avibactam (MIC >128/4 mg/L). Both S1-PFGE-Southern blotting and whole genome sequencing revealed that the carbapenemase genes and were carried by the same IncFII:IncR:IncN hybrid plasmid (pKPC2_NDM5). Conjugation experiments indicated that pKPC2_NDM5 was a non-conjugative plasmid.

Conclusion: This is the first report of a hybrid plasmid carrying both carbapenemase genes and in a clinical ST11 isolate that confers resistance to both ceftazidime/avibactam and carbapenems, thereby presenting a serious threat to treatment in clinical practice.