GFP tagged Vibrio parahaemolyticus Dahv2 infection and the protective effects of the probiotic Bacillus licheniformis Dahb1 on the growth, immune and antioxidant responses in Pangasius hypophthalmus

In this study, the pathogenicity of GFP tagged Vibrio parahaemolyticus Dahv2 and the protective effect of the probiotic strain, Bacillus licheniformis Dahb1was studied on the Asian catfish, Pangasius hypophthalmus. The experiment was carried out for 24 days with three groups and one group served as the control (without treatment). In the first group, P. hypophthalmus was orally infected with 1 mL of GFP tagged V. parahaemolyticus Dahv2 at two different doses (105 and 107 cfu mL−1). In the second group, P. hypophthalmus was orally administrated with 1 ml of the probiotic B. licheniformis Dahb1 at two different doses (105 and 107 cfu mL−1). In the third group, P. hypophthalmus was orally infected first with 1 mL of GFP tagged V. parahaemolyticus Dahv2 followed by the administration of 1 mL of B. licheniformis Dahb1 (combined treatment) at two different doses (105 and 107 cfu mL−1). The growth, immune (myeloperoxidase, respiratory burst, natural complement haemolytic and lysozyme activity) and antioxidant (glutathione-S-transferase, reduced glutathione and total glutathione) responses of P. hypophthalmus were reduced after post infection of GFP tagged V. parahaemolyticus Dahv2 compared to control. However, after administration with the probiotic B. licheniformis Dahb1 at 105 cfu mL−1, P. hypophthalmus showed significant increase in the growth, immune and antioxidant responses compared to 107 cfu mL−1. On the otherhand, the growth, immune and antioxidant responses of P. hypophthalmus infected and administrated with combined GFP tagged Vibrio + Bacillus at 105 cfu mL−1 were relatively higher than that of GFP tagged V. parahaemolyticus Dahv2 and control groups but lower than that of probiotic B. licheniformis Dahb1 groups. The results of the present study conclude that the probiotic B. licheniformis Dahb1 at 105 cfu mL−1 has the potential to protect the P. hypophthalmus against V. parahaemolyticus Dahv2 infection by enhancing the growth, immune and antioxidant responses. The probiotic B. licheniformis Dahb1 would be effectively used in the treatment of aquatic diseases for improvement of aquaculture industry. [Display omitted] •Probiotic effect of Bacillus licheniformis Dahb1 was studied in Asian catfish.•B. licheniformis Dahb1 improved the growth.•B. licheniformis Dahb1 enhanced the innate immune responses.•B. licheniformis Dahb1 increased the antioxidant enzyme responses.