Abstract:
Objective To elucidate the molecular mechanism by which the carbapenemase-encoding plasmid p21QH43K-KPC is transferred from Klebsiella pneumoniae to Escherichia coli, and mediates low-level resistance to carbapenem drugs in E. coli.
Method The construction of EZ-Tn5 transposon mutation library, CRISPR-Cas9-mediated gene knockout, transcriptome sequencing and whole genome sequencing (WGS) were used to determine the regulatory mechanism of low-level resistance to meropenem mediated by the blaKPC-2 gene in E. coli.
Result A transposon mutant EC600/p21QH43K-KPC-130 with enhanced meropenem resistance (MIC=8.000 mg/L) was obtained by constructing the EZ-Tn5 transposon mutation library of the EC600/p21QH43K-KPC conjugon. WGS and Mauve analysis revealed that the transposon had inserted into one chromosomal gene ompR, and two point mutation genes of iron and ltrA were found. However, through gene knockout, only ompR deletion mutants exhibited reduced sensitivity to carbapenem that could be restored by gene complementation.
Conclusion The molecular mechanism of the blaKPC-2 gene encoded on the plasmid mediating low-level resistance to carbapenems in E. coli is related to the regulation of blaKPC-2 gene by ompR.