益生菌促進澳洲淡水龍蝦特定免疫活性及抗白點病毒之潛力

Abstract

WSSV是蝦的主要病毒性病原之一。其造成的感染不只發生在蝦，也包含其他海水及淡水的甲殼類如螃蟹和螯蝦。WSSV在全球已造成龐大的經濟損失，目前仍沒有有效的防治方式。與擁有先天性及適應性免疫的脊椎動物不同，屬於無脊椎動物的蝦僅靠數種先天性免疫反應抵抗病原感染。水產養殖已使用益生菌來提升養殖物種之免疫能力。本研究分別使用三種已被證實具有提升免疫能力的益生菌：Lactobacillus reuteri Pg4、Bacillus subtilis AC 及 B. licheniformis CK，嘗試找出具有提升蝦特定免疫能力及抗WSSV潛力的益生菌。在免疫激發試驗中，上述三種益生菌都能在兩周內有效提升蝦的酚氧化酵素及超氧歧化酶活性。而在WSSV感染試驗中，餵食兩株Bacillus菌株的蝦存活率最高，進一步進行存活蝦免疫分析發現，B. subtilis AC能在WSSV感染下持續促進蝦酚氧化酵素及超氧歧化酶活性，導致存活率上升。腸道菌相分析結果說明感染WSSV會造成菌相顯著變化，而L. reuteri Pg4及B. subtilis AC具有降低因受病毒感染而提升的菌屬之能力。此結果說明B. subtilis AC為最具有抗WSSV潛力的益生菌。

White spot syndrome virus（WSSV）is a major pathogen of aquacultured shrimp. The infection of WSSV occurs not only in shrimp but also in other marine and freshwater crustaceans, including crabs and crayfishes. WSSV has caused large economic losses and there is still no adequate treatment. Unlike vertebrate immunity which is composed of both innate and adaptive responses, invertebrates rely on multiple innate defense reactions to combat infections. However, probiotics have been used in aquaculture for the function of immune stimulation. In this study, three probiotics were used respectively as feed additive: Lactobacillus reuteri Pg4, Bacillus subtilis AC and B. licheniformis CK, all of which have been proved to increase the immune responses in vitro or in vivo experiments. In immune test, both of phenoloxidase（PO）and superoxide dismutase（SOD）activities in probiotic treated groups were significantly higher than normal feed group. In WSSV challenge test, the two Bacillus strains caused the highest survival rate compared to other groups, and the higher PO and SOD activities were also found in the survival shrimps in B. subtilis group. On the other hand, the results of intestinal microbiota analysis proved that WSSV infection could significantly influence the intestinal microbiota, while the L. reuteri Pg4 and B. subtilis AC could decrease some bacteria genera raised by WSSV infection. In conclusion, B. subtilis is the most effective probiotic among three probiotics to improve the survival rate against WSSV infection.