Dietary administration of a host-gut derived probiotic Bacillus amyloliquefaciens COFCAU_P1 modulates immune-biochemical response, immune-related gene expression, and resistance of Labeo rohita to Aeromonas hydrophila infection

The purpose of this study was to evaluate the dietary effects of Bacillus amyloliquefaciens COFCAU_P1 on immune-biochemical response, immune-related gene expression and resistance of Labeo rohita against Aeromonas hydrophila infection. Fingerlings of L. rohita were fed with three B. amyloliquefaciens-supplemented diets (1 x 10(7), 1 x 10(8) and 1 x 10(9) cells g(-1) of diet) for 30 days. Different innate immune parameters, biochemical responses and immune-related gene expression were measured at the end of the 10, 20 and 30 days of feeding. Control and test fish were challenged intraperitoneally by A. hydrophila after 30 days of experimental feeding. Mortality was observed and cumulative mortality percentage was calculated. The immunological (superoxide anion, myeloperoxidase and antiprotease) and biochemical (total protein, albumin and globulin) responses were significantly (p < 0.05) enhanced, particularly by 1 x 10(8) and 1 x 10(9) B. amyloliquefaciens cells g(-1) of diet after 20 and 30 days of feeding. Immune-related genes viz. IL-1 beta and TNF-alpha showed significantly higher expression in head-kidney and liver tissues. All the B. amyloliquefaciens-supplemented diets significantly (p < 0.05) enhanced the survival of L. rohita against A. hydrophila. The results collectively suggest the prospect of B. amyloliquefaciens COFCAU_P1 as an effective probiotic for aquaculture. The efficacy of the strain in reducing A. hydrophila-induced mortalities is also note-worthy.