Characterization and Analysis of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) in Pandemic and Non-Pandemic Vibrio parahaemolyticus Isolates from Seafood Sources

Vibrio parahaemolyticus is one of the significant seafood-borne pathogens causing gastroenteritis in humans. Clustered regularly interspaced short palindromic repeats (CRISPR) are commonly detected in the genomes of V. parahaemolyticus and the polymorphism of CRISPR patterns has been applied as a genetic marker for tracking its evolution. In this work, a total of 15 pandemic and 36 non-pandemic V. parahaemolyticus isolates obtained from seafood between 2000 and 2012 were characterized based on hemolytic activity, antimicrobial susceptibility, and CRISPR elements. The results showed that 15/17 of the V. parahaemolyticus seafood isolates carrying the thermostable direct hemolysin gene (tdh+) were Kanagawa phenomenon (KP) positive. The Multiple Antibiotic Resistance (MAR) index ranged between 0.1 and 0.4, and 45% of the isolates have an MAR index ≥ 0.2. A total of 19 isolates were positive for CRISPR detection, including all tdh+ trh− isolates, two of tdh− trh+, and each of tdh+ trh+ and tdh− trh−. Four spacer types (Sp1 to Sp4) were identified, and CRISPR-positive isolates had at least one type of spacer homolog to the region of Vibrio alginolyticus megaplasmid. It is of interest that a specific CRISPR profile and spacer sequence type was observed with correlations to the hemolysin genotype (tdh/trh). Thus, these provide essential data on the exposure of foreign genetic elements and indicate shared ancestry within different genotypes of V. parahaemolyticus isolates.