Abstract
Klebsiella variicola (K. variicola ) is an emerging human pathogen, which poses a threat to public health. The horizontal gene transfer (HGT) of plasmids is an important driver for the emergence of multiple antibiotic-resistant K. variicola . The clustered regularly interspersed short palindromic repeats coupled with the CRISPR-associated genes (CRISPR/Cas) constitute an adaptive immune system in bacteria, which provide acquired immunity against HGT. However, the information about CRISPR/Cas system in K. variicolais still limited. In this study, a total of 487 genomes from NCBI database were used to analyze the characterization of CRISPR/Cas systems. 105 of the 487 genomes harbored at least one confirmed CRISPR array. Three types of CRISPR/Cas system, including types I-E, I-E*, and Ⅳ-A systems, were identified among 105 strains. The distribution of type I system was strongly associated with MLST, whereas type IV system was randomly distributed. Approximately one-third of spacer origins were homologous with plasmids or phages, indicating the role of CRISPR/Cas systems in controlling HGT. Moreover, spacers in K. variicolatended to target mobile genetic elements (MGEs) from Klebsiella pneumoniae , which provides new evidence for their interaction during evolution. Collectively, our results provide valuable insights into the role of CRISPR/Cas systems in K. variicola .