四種弧菌對養殖草蝦及斑節蝦之致病性研究

Abstract

本研究利用六株不同來源的四種弧菌(Vibrio)進行其全菌（Whole cell ）及細胞外產物（ Extracellular Product ，ECP ）對草蝦及斑節蝦的致病性探討。V. damsela． UAH - 1 由弧病草蝦所分離，二株 V. anquillarum; UAH- 2 及 UAH-3 分別由弧菌病香魚及外觀健康草蝦之肝胰腺所分離。二株 V． alginolyticus ; UAH -4 及 UAH- 5 分別由外觀健康草蝦之肝胰腺及腸中所分離。V. vulnificus UAH- 6 亦由外觀健康草蝦之腸所分離。 6 株細菌之澱粉?( Amylase ) ，幾丁質?（Chitinase ) ，脂肪?（ Lipase ) ，及白明膠?（ Gelatinase ）反應均呈陽性。 6株細菌細胞外產物中 4 株對兔子及鰻魚的紅血球都有溶血性， UAH-4 及 UAH-6 則無。生理活性最適宜之 pH 值一般均介於 pH8 - 9 之間，但 UAH-5 則為 pH4 。作用於 Chinese hamster ovary cell 有拉長現象。對兔子皮內血管通透性沒有影響。 各菌株 ECP 經 DEAE-Sephacel 及 SDS 一 PAGE 處理之半純化後產物顯示有 2 ?5 種分離帶，分子量介於 20 KD 至 70 KD 間.各菌株間有部份相同。 肌肉注射結果顯示 whole cell 對草蝦之 LD50（ Log10 cfu / 10g B • W . ）為 5.71 ? 6.74 ，對斑節蝦為 5.67? 6 . 89 。細胞外產物對草蝦之 LD50（ ug / 10g B. W . ）為 99 . 0 ? 282 . 85 ，而對斑節蝦則為 72.42 ? 265.27 之間。 組織病變，草蝦以全菌接種時均無肉眼可見病變，斑節蝦則會在接種部位產生白濁壞死的病灶。細胞外產物接種時，草蝦及斑節蝦則均可見白濁壞死的病灶。組織切片中所有接種試驗蝦的肌肉及類淋巴器官均出現壞死或肉芽腫病灶。肝胰腺則僅有部份出現壞死及肉芽腫病灶，其他器官則多未出現病變。

Six strains of different sources of V. damsela, V. anguillarum, V. alginolyticus and V. vulnificus were collected for study on pathogenicity to Giant tiger prawn and Kruma prawn. All six strains were Amylase, Chitinase, Lipase and Gelatinase positive. The pathogenicity experiments were tested by whole cell and Extracellular products (ECP) preparation. No gross finding could be observed in the Giant tiger prawn, when the whole cell IM injected. While in IM injected of whole cell to Kruma prawn and ECP injected to both kind of prawn, all developed opaque necrosis in site of injection. Histopathologic observation showed that necrosis and/or granulomatosis developed in all experimental prawn. But, only occasionally noted in hepatopancrea, and it were not formed in other organs in most cases. LD50 of whole cell injection(Log10 cfu/10g B.W.)to Giant tiger prawn and Kruma prawn were 5.71 to 6.74 and 5.67 to 6.89 respectively. While LD80 of ECP injection(ug/10g B.W.)were 99.0 to 282.85 and 72.42 to 265.27. Preliminary tests of the ECP from 6 strains show that they are slightly variaed in the following properties; hemolysis to rabbit and eel RBC, optimal pH value for physiological activity, action on chinese hamster ovary cell and rabbit intradermal vascular permeability. Semi—purified of the ECP, by treated with DEAE-Sephacel followed by SDS-PAGE show that 2 to 5 bands of 20 KD to 70 KD were presented in each ECP. 30KD and 40KD bands presented in most strains. While 70KD band presented in only one strains.