Species Richness and Diversity of Gut Microbiota may Reduce AHPND in the Whiteleg Shrimp, Litopenaeus vannamei

Acute hepatopancreatic necrosis disease (AHPND) causes massive economic loss in shrimp culture sector. Eco-friendly feed additives, which can reduce antibiotic resistance in bacteria and antibiotic residues present in aquaculture products, have become popular in shrimp farming. These additives have proven to maintain a balance host gut microbiota in preventing pathogen infection. In the present study, gut microbiota of Litopenaeus vannamei, which had been administrated with different diets (probiotic: Bacillus B2; prebiotic: Gracilaria changii, G; and a combination of Bacillus B2 and G. changii, B2+G) and post-challenged with AHPND-causing Vibrio parahaemolyticus strain 3HP, was determined using the PCR-DGGE method. The results showed that the gut microbiota of L. vannamei was dominated by the phylum Proteobacteria. The abundance of Proteobacteria was higher in the B2+G and G treatment groups. High abundance of native gut microbiota, such as Proteobacteria might prevent the adhesion of virulent bacteria by competitive exclusion, and thus, reducing the chance of AHPND infection. Moreover, the shrimp from the B2+G treatment group with higher survival in the challenge tests possessed a higher diversity and species richness of gut microbiota. This suggests that higher diversity and species richness of beneficial gut microbiota probably interfering bacterial communication among the pathogens by either destructing or neutralising their quorum sensing signals. Consequently, this will prevent the colonisation of pathogens in the gut and resulted in a higher survival of the shrimp challenged with V. parahaemolyticus.