Modulation of innate immunity, expression of cytokine genes and disease resistance against Aeromonas hydrophila infection in goldfish (Carassius auratus) by dietary supplementation with Exiguobacteriwn acetylicum S01

摘要

Probiotic strains play an increasing role in the production of healthy animals used as a food source. Elucidating the mechanisms of action that allow probiotic-driven immunomodulation may facilitate different applications such as the prevention of infectious diseases in food organisms. This study elucidates the probiotic effects of Exiguobacteriwn acetylicum S01 on the growth, haematological profile, innate immune capacity, expression of cytokine genes, and resistance to diseases of Carassius auratus caused by Aeromonas hydrophila infection. Three fish groups were fed with the following diets containing different doses of E. acetylicum S01(CFU g(-1)): basal diet 0 (BD, without probiotic), 2.5 x 10(7) (DI) and 2.7 x 10(9) (DII)-CFU g(-1) for 4 weeks. After 4 weeks, the fish were injected intraperitoneally with A. hydrophila and the percentage of survival was recorded over 21 days of post-challenge. Results revealed that dietary supplementation of E. aceodiewn S01significantly (P & 0.05) enhanced the growth, haematological profile and cellular immune responses including respiratory burst, phagocytic activities and antimicrobial enzymes (myeloperoxidase and lysozyme) and total immunoglobulin levels were improved by probiotic feeding at both occasions. Comparatively, expression of c- and g-type lysozyme followed by pro- and anti-inflammatory cytokines (IL-beta,IL-10 and TGF beta) was up-regulated in kidney, head-kidney and spleen. Moreover, fish fed with diet DII had a significantly higher (P & 0.05) survival rate (73.2%) after challenging. The survival rate was only 33.2% of the BD group against A. hydrophila infection. Our results revealed that E. acetylicum S01 delivered probiotic in feed exerts its influence on growth performance and provides disease resistance by stimulating the immune system at the cellular and molecular levels in C. auratus.