餵食乳酸菌對海鱺抗發光桿菌症之保護作用

Abstract

海鱺(Rachycentron canadum)是台灣海水箱網水產養殖重要的魚種,然而 海鱺漁業受到發光桿菌症(photobacteriosis)嚴重危害,病原為美人魚發光桿菌 殺魚亞種(Photobacterium damselae subsp. piscicida, Pdp)。目前雖以抗生素及疫 苗來防範疫情,但效果仍有限。 本研究探討一株分離自海鱺腸道的乳酸菌 (Pediococcus pentosaceus strain 4012, LAB4012),於體外實驗中發現 LAB4012 的 胞外分泌物會抑制 Pdp 生長;而在 Pdp 浸泡攻毒實驗中,海鱺苗經餵食含 LAB4012 的飼料兩週後,其相對存活率(Relative percent survival, RPS)可達 80%,餵食四週後攻毒,相對存活率更高。而且餵食 LAB4012 兩週後,海鱺的成 長率比起沒有餵食的對照組高12%。雖然海鱺餵食 LAB4012 兩週後,無法增強周 邊血液白血球的吞噬活性(phagocytosis activity),但其呼吸爆活性(respiratory burst)卻顯著提高。以 Pdp 去活化疫苗免疫海鱺後,發現餵食 LAB4012 並不會 提高魚體內的專一性免疫反應,但在Pdp浸泡攻毒實驗中,卻可使免疫魚再提高 20%的存活率,造成加成保護效果的原因極可能與 LAB4012 所誘發之先天免疫反 應有關。綜合以上特性,證明 LAB4012 乳酸菌可作為海鱺抗 Pdp 感染之益生菌。

Cobia (Rachycentron canadum) is an important fish species for marine-cage aquaculture in Taiwan. However, cobia industry has been severely damaged by photobacteriosis, which is caused by Photobacterium damselae subsp. piscicida (Pdp). Antibiotics and vaccines have been applied for the control of Pdp infection, but the efficacy is not consistent. In this study, one lactic acid bacteria, Pediococcus pentosaceus strain 4012 (LAB4012), was isolated from the intestine of cobia, was investigated, and it was found that the culture supernatant of LAB4012 was able to inhibit Pdp growth in vitro. In the Pdp immersion challenge test, the relative percentage of survival (RPS) in cobia fed with LAB4012 for 2 weeks was 80%, and it was even higher in cobia for 4-week LAB4012-feeding. Furthermore, the body weight of the cobia after 2-week feeding with LAB4012 was 12% higher than that of non-fed control group. Although feeding with LAB4012 did not enhance the phagocytic activity of peripheral blood leukocytes (PBLs), but the respiratory burst of PBLs was significantly elevated. Feeding with LAB4012 did not improve the specific immune response of cobia after immunization with inactivated Pdp, but significantly increased 20% survival rate after Pdp challenge. The synergetic protection is highly possible related with LAB4012-induced innate immunity. In summary, LAB4012 is suggested to be a probiotic for cobia against Pdp infection.