The effectiveness of marine bacterial microcapsules in controlling vibriosis disease caused by the infection of Vibrio parahaemolyticus in white shrimp Litopenaeus vannamei

Vibriosis is a major bacterial disease in shrimp farming, which is caused by Vibrio spp. It has resulted in substantial shrimp mortality. One strategy to control this disease is to use microcapsules containing marine bacteria. This study was established to evaluate the effectiveness of such microcapsules in controlling vibriosis in white shrimp. The shrimps were fed a diet with microcapsules containing three different bacteria, namely, Bacillus subtilis P2.24, Brevibacterium casei D6.6, and Bacillus altitudinis D6.19, for 30 days. The shrimps were then tested by injecting Vibrio parahaemolyticus (10(6) CFU/mL) on the 31st day. The administration of microcapsules containing the three marine bacteria had a positive effect on white shrimp. The microcapsules with B. subtilis P2.24 showed the best effectiveness as an anti-vibriosis agent, as indicated by the high survival rate after 7 days of challenge test, which was 40% higher than that in the positive control (Duncan's test p < 0.05). Furthermore, the microcapsules containing the three marine bacteria promoted immune responses [i.e., total hemocyte count, percentage of semi-granular/granular cells, phenoloxidase activity, respiratory burst, and immune-related gene expression], microbiota diversity, and total viable bacterial count in shrimp intestinal tract. In addition, the microcapsules reduced the total Vibrio count and total V. parahaemolyticus count in shrimp intestinal tract, as well as the damage to hepatopancreas and muscle. In conclusion, the B. subtilis P2.24 isolate is a potential vibriosis biocontrol agent and an alternative for preventing vibriosis.