Vibrio parahaemolyticus O10:K4: An Emergent Serotype with Pandemic Virulence Traits as Predominant Clone Detected by Whole-Genome Sequence Analysis - Beijing Municipality, China, 2021.

ABSTRACT

Introduction: Vibrio parahaemolyticus (V. parahaemolyticus) is a common foodborne pathogen which causes gastroenteritis in humans, especially the O3K6 pandemic clone which is still a prominent serotype in Beijing, China. In this study, we observed a novel serotype O10K4 isolated from clinical diarrhea cases, which became the most prevalent clone in 2021. Methods: 73 clinical isolates were collected through sentinel hospitals' surveillance in 2021. Serum agglutination testing and antimicrobial susceptibility testing were conducted. Whole genome sequencing was applied to characterize 73 V. parahaemolyticus strains and complete phylogenetic analysis. Results: Seven serotypes were identified among 73 strains. O10K4 was the most common serotype (83.6%), followed by O2KUT, O4KUT, and O1KUT. Multilocus sequence typing divided the 73 isolates into 10 sequence types (STs) with ST3 as the most prevalent, which covered all O10K4 strains. Most isolates were sensitive to common antimicrobial agents apart from colistin. All the O10K4 isolates were positive for the thermostable direct hemolysin gene, toxRS/new, andorf8, and negative for the TDH-related hemolysin gene. The whole genome sequencing-single nucleotide polymorphism phylogenetic analysis revealed O10K4 strains formed a main genetic lineage, which was genetically distinct from other serotypes. We also demonstrated the presence of two type III secretion system genes (T3SS1 and T3SS2) and ß lactamase resistance gene blaCARB-22 in all O10K4 strains. Conclusions: The study confirmed the emergence of V. parahaemolyticus O10K4 possessing virulence factors similar to the O3K6 pandemic clone, which may have enabled them to become prevalent in Beijing, China.