Investigation of toxin genes and potential to control early shrimp mortality disease of chitosan on some Vibrio parahaemolyticus strains isolated from Mekong Delta

Acute Hepatopancreatic Necrosis Disease (AHPND) is a disease that induces mass early mortality in shrimp caused by Vibrio parahaemolyticus. This bacterium is capable of secreting biofilm - the main element in the host invasion mechanism and also protects V. parahaemolyticus from anti-bacterial agents, especially antibiotics. In this study, 03 strains of V. parahaemolyticus isolated from infected shrimp samples were investigated for toxin genes. They had the toxR gene and lacked tdh, trh and pPVA3-1 virulence plasmid genes. Chitosan was used to inhibit and destroy their biofilm biosynthesis in order to prevent AHPND. The minimum chitosan concentration inhibiting biofilm biosynthesis was 2 g/L. At 3 g/L, chitosan was capable of destroying 87.78 - 88.74% of the formed film. Biofilm analysis before and after treatment with chitosan showed that the EPS rate after treatment was reduced by 68-72.73% compared to that before treatment. The results demonstrated the potential of chitosan in the prevention of AHPND.