Abstract: Clustered regularly interspaced short palindromic repeats (CRISPRs) are?an adaptive, heritable immune system found in prokaryotes that confers resistance to exogenous?genetic?elements?such as phage. CRISPRs are considered an ideal target for molecular subtyping because they have a high diversity and carry traceable genetic information. In this study, the genomic CRISPR structure in 86 strains of Campylobacter jejuni isolated in Jiangsu province was analyze by bioinformatic methods. The results showed that 36% of these strains contained CRISPRs in their genomes and 32 strains were found to have only one CRISPR 92–366 bp in length. The direct repeats detected in this study were identical to those in the CRISPR database. A total of 111 spacers were recognized and they were classified into 17 different clusters based on their sequences, 10 clusters of which have been previously recorded in the CRISPR db database while the 7 others were reported for the first time, consisting of 55 (49.5%) of the 111 spacers. Homology analysis showed that there was a high similarity in the spacer sequences between different phages and plasmids from the same genus or species as well as those from other pathogenic bacteria, which suggested that horizontal gene transfer (HGT) may play an important role in the bacterial communication between C. jejuni and other pathogens. Besides, 38 wild strains of C. jejuni were grouped into 5 patterns based on the CRISPR structure diversity. The results of this study can provide essential data for subsequent molecular subtyping and traceability of C. jejuni.

Key words: Campylobacter jejuni, clustered regularly interspaced short palindromic repeats (CRISPR), direct repeats, spacers, homology