Characterization of a and CRISPR-Cas System Co-harboring Plasmid in a Carbapenemase-Producing High-Risk ST11 Strain.

We set out to study the prevalence of the gene in carbapenemase-producing (CPKP) strains, and to determine whether its presence is associated with a fitness cost. A total of 234 clinical CPKP isolates were collected from a tertiary medical center in Taiwan from January 2018 to January 2019. The and carbapenemase genes were detected by polymerase chain reaction (PCR) followed by Sanger sequencing. The -positive carbapenemase-producing strain was characterized by whole genome sequencing, a plasmid stability test and a conjugation assay. growth rate and an virulence test were compared between the parental -positive strain and its plasmid-cured strain. We identified only one positive strain (KP2509), co-harboring and , among 234 (1/234, 0.43%) CPKP strains. KP2509 and its transconjugant showed moderate colistin resistance (MIC = 8 mg/L). The is located on a large conjugative plasmid (317 kb), pKP2509-MCR, with three replicons, IncHI, IncFIB, and IncN. Interestingly, a complete Type IV-A3 CRISPR-Cas system was identified in pKP2509-MCR. Plasmid pKP2509-MCR was highly stable in KP2509 after 270 generation of passage, and the pKP2509-MCR cured strain PC-KP2509 showed similar growth rate and virulence in comparison to KP2509. The prevalence of in CPKP strains remains low in our center. Notably, we identified a large plasmid with multiple replicons containing both the and the Type IV-3A CRISPR-Cas genes. The further spread of this highly stable plasmid raises concern that it may promote the increase of prevalence in CPKP.