Complete genome sequence of highly pathogenic Vibrio parahaemolyticus isolated from mariculture Penaeus vannamei reveals virulence factor genes

The complete genomic sequence of Vibrio parahaemolyticus strain HN1 was determined. The HN1 genome consisted of two circular chromosomes, with a total length of 5,024,488 bp and a G + C content of 45.16%. In total, 4,580 coding genes with an average length of 944 bp were identified. Among them, 3,818 genes (83.36%) were annotated to the Clusters of Orthologous Groups (COG) database; 2,811 (61.38%) to the Gene Ontology (GO) database; and 2,493 (54.43%) to the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. A genetic virulence analysis identified 577 virulence genes, including cya, flagellum-related genes, Bsa T3SS, p60 and the type IV secretion system in V. parahaemolyticus strain HN1. Meanwhile, hemolysin was identified as a virulence protein. In a further analysis, no thermostable direct hemolysin (TDH) or TDH-related hemolysin (TRH) was identified, but thermolabile hemolysin (TLH) was identified. In a secretory system analysis, genes associated with the type I, type II, type III, and type VI secretory systems were identified. The type III (located on chromosome 1) and type VI secretory systems (located on chromosome 1 and chromosome 2) were annotated by multiple genes and may play an important role in the strong pathogenicity of V. parahaemolyticus in shrimp. In addition, multiple drug resistance genes were identified and antibiotic-susceptibility assays were performed.