In Silico and In Vitro Investigation of Phytochemicals Against Shrimp AHPND Syndrome Causing PirA/B Toxins of Vibrio parahaemolyticus.

In Southeast Asia, the penaeid shrimp aquaculture production faces a new pandemic bacterial disease called acute hepatopancreatic necrosis disease (AHPND). The highly profitable pacific white shrimp, Litopenaeus vannamei, has become a challenging species due to severe lethal infections. Recent research has identified a critical pathogen, Vibrio parahaemolyticus, which caused significant loss in the shrimp industry. The disease pathway involves a virulence plasmid encoding binary protein toxins (PirA/B) that cause cell death. The protein toxins were inherited and conjugatively transferred to other Vibrio species through a post-segregational killing system. In this study, "in silico" (Glide, 2021) analysis identified four phytocompounds as myricetin (Myr), ( +)-taxifolin (TF), (-)-epigallocatechin gallate (EGCG), and strychnine (STN) which could be most effective against both the toxins concerning its docking score and affinity. The interactions of complexes and the critical amino acids involved in docking were analyzed using the Discovery Studio (version 2016). Molecular dynamic studies showed lower root mean square deviations (RMSD) and improved stabilization of ( +)-taxifolin (TF) and (-)-epigallocatechin-3-gallate (EGCG) against both the protein toxins. The antibacterial potential of all four selected compounds had tested against pathogenic strains of V. parahaemolyticus through minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The best MBC results were observed at concentrations of 1 mg/mL for EGCG and 1.25 mg/mL for TF. Moreover, the complete reduction of viable cell counts in the in vitro bactericidal activity had recorded after 24 h of incubation.