Paenibacillus polymyxa as a water additive improved immune response of Cyprinus carpio and disease resistance against Aeromonas hydrophila

The present study was undertaken to investigate the impact of Paenibacillus polymyxa as water additive probiotic bacterium in common carp, Cyprinus carpio based on water quality, survival, innate immune responses and disease resistance. The completely randomized experiment design was conducted for eight weeks and treatments consisted of three levels of P. polymyxa added in water at concentration of 103 cfu mL−1 (PP1), 104 cfu mL−1 (PP2) and 105 cfu mL−1 (PP3) and one control (Con, without any probiotic). No significant differences (p > 0.05) in water quality parameters, such as temperature, pH, dissolved oxygen, ammonical nitrogen and nitrite nitrogen were observed throughout the experimental period among treatments. The influences of P. polymyxa at different concentrations significantly improved survival (p < 0.05). Study of different innate immunological parameters viz. lysozyme activity, respiratory burst assay, myeloperoxidase content, catalase and superoxidase dismutase activities showed significant (p < 0.05) improved immune responses in fish exposed to P. polymyxa as water additive at 103 (PP1) and 104 (PP2) cfu mL−1. The supplementation of probiotic in challenge test significantly (p < 0.05) enhanced the resistance of fish against A. hydrophila infection. In view of recent reports of antibiotic failure from many countries to stop spread of fish diseases, renewed interest in a more complete understanding of the fish immune response to infectious diseases will be critical in developing new eco-friendly control strategies for future. Therefore, the application of probiotic P. polymyxa as water additive could be applied in aquaculture to improve immune responses and disease resistance of C. carpio.