Genomic Features of Vibrio parahaemolyticus from Lebanon and Comparison to Globally Diverse Strains by Whole-Genome Sequencing.

Gastroenteritis is a disease that can be caused by virulent strains of Vibrio parahaemolyticus in humans upon the consumption of contaminated seafood. In summer 2017, a sudden increase in the number of patients suffering from gastroenteritis due to a V. parahaemolyticus infection was observed at the Middle East Institute of Health University Hospital in Lebanon. The aim of this study was to analyze the isolates recovered from stool specimens, and to compare them using different phenotypic assays, genomic profiling techniques, and whole-genome sequencing, to achieve a better understanding of the current V. parahaemolyticus strains available in Lebanon. Virulence potential was analyzed based on the detection of the hemolysins: thermostable direct hemolysin (tdh), thermostable direct hemolysin-related hemolysin (trh), and thermolabile hemolysin (tlh). Resistance was determined by testing antibiotic susceptibility and performing PCR assays for β-lactamases and quinolone resistance determinants. Genetic relatedness was verified by multilocus sequence typing, pulsed-field gel electrophoresis, and whole genome-based single nucleotide polymorphism analysis. All of the isolates had the tdh+, trh-, group-specific PCR+ genotype, which is a characteristic of the O3:K6 pandemic clone. The isolates were resistant to ampicillin (100%), ceftazidime (86%), ticarcillin (14%), and amikacin (14%), belonged to the sequence type ST3, and had very similar phylogenetic fingerprints. The isolates undertaken in this study exhibited almost identical resistance, virulence, and phylogenetic patterns, confirming an outbreak linked to the spread of the pandemic O3:K6 serotype in the country.