大肠埃希氏菌引起的虹鳟鱼病的初步研究

ESCHERICHIA COLI AS A PATHOGEN IN RAINBOW TROUT (ONCORHYNCHUS MYKISS)

1988年,山西省虹鳟鱼试验场的二龄虹鳟发生一种流行病,病鱼典型症状为:体色发黑,鳃丝苍白或粉红,肛门及有的鳍条充血,内脏肠、肝、脾等充血和出血。病原菌为革兰氏阴性,杆状,0.9—1.2×2.3—4.5μm,周鞭毛、能运动,周身还有菌毛(Pili)。能还原硝酸盐为亚硝酸盐;氧化酶阴性;葡萄糖发酵并产气,甲基红和靛基质试验阳性,V-P试验阴性;不产生尿素酶,苯丙氨酸脱氨酶和硫化氢:不利用丙二酸钠;不液化明胶;在KCN培养基和枸橼酸盐琼脂上不生长;发酵蔗糖、麦芽糖、甘露醇、水杨苷、山梨醇、阿拉伯糖、棉子糖;不发酵卫矛醇、侧金盏花醇、肌醇、乳糖,纤维二糖、α-甲基-D葡萄糖苷;微发酵木糖和鼠李糖;赖氨酸脱羧酶和精氨酸双水解酶反应阳性;鸟氨酸脱羧酶阴性;该菌DNA中G+Cmol％为51.04(Tm)。据上所述,该菌属于大肠埃希氏菌(Escherichia coli)其特性和对鱼的致病性不同于以前所报道的肠杆菌科中的鱼类致病菌。

This paper describes the symptoms of an epizootic in yearling rainbow trout caused by E. coli and an epidemic in a fish farm in Shanxi Province. The acute infected disease was characterized by darkening of body colour, reddening of anus and some fins and anemia in gill filaments. Internally, the intestine, liver and spleen were congestive and hemorrhagic. All bacterial isolates were Gram-negative. They were rod-like in shape with peritrichous flagella and fimbriae (pili), measuring 0.9—1.2×2.3—4.5μm. The bacteria were mobile, oxydase negative, M. R. and Indol positive, V. P., and urease and phenylalanine deaminase negative. They could produce acid and gas from glucose and reduce nitrate to nitrite, but did not utilize sodium malonate. Tests on production of hydrogen sulfide, liquafaction of gelatin and growth in KCN medium were negative. Moreover, they fermented D-sorbitol, D-mannitol and L-arabinose, but could not fermentt adonitol, lactose or cellobiose. The Mol％ G+C of the DNA is 51.04(Tm). The isolated organisms were identified as Escherichia coli and were differentfac Enterobacteriaceae from any formerly established species of the familyfac that act as causative agents of fish disease.