Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) have disseminated worldwide and emerged as major threats to public health. Of epidemiological significance, the international pandemic of KPC-KP is primarily associated with CG258 isolates and blaKPC-IncF plasmids. CRISPR-Cas system is an adaptive immune system that can hinder gene expansion driven by horizontal gene transfer. Because of blaKPC-IncF plasmids are favored by CG258 K. pneumoniae, it was of interest to examine the co-distribution of CRISPR and blaKPC-IncF plasmids in such isolates. We collected 459 clinical K. pneumoniae isolates in China and collected 203 global whole-genome sequences in GenBank to determine the prevalence of CRISPR-Cas systems. We observed that CRISPR-Cas system was significantly scarce in the CG258 lineage and blaKPC-positive isolates. Furthermore, the results of conjugation and plasmid stability assay fully demonstrated the CRIPSR-Cas system in K. pneumoniae could effectively hindered blaKPC-IncF plasmids invasion and existence. Notably, most blaKPC-IncF plasmids were also proved to be good targets of CRISPR owing to carry matched and functional protospacers and PAMs. Overall, our work suggests that type I-E CRISPR-Cas systems could impact the spread of blaKPC in K. pneumoniae populations, and the scarcity of CRISPR-Cas system was one of potential factors leading to the propagation of blaKPC-IncF plasmids in CG258 K. pneumoniae.
Keywords: CRISPR-Cas; Klebsiella pneumoniae clonal complex 258; carbapenem resistance; horizontal gene transfer; plasmids.