一株凡纳滨对虾病原菌的分离、鉴定及其致病力分析

从患病凡纳滨对虾肝胰腺中分离出菌株20100612001,经人工感染实验证实,该分离菌株对凡纳滨对虾的半数致死量为1.44×106CFU/ml。形态学观察和革兰氏染色表明,该菌株为革兰氏阴性,无芽孢,有一根端极鞭毛;呈球杆状、球状、棒状或梨状且有两极浓染现象;在2216E培养基上为透明或半透明的圆形菌落,而在TCBS选择性培养基上为绿色或蓝绿色菌落。经Biolog碳源利用反应、脂肪酸气相色谱分析得出,该菌株与副溶血弧菌、需钠弧菌等的生理生化特性最相似;16SrD-NA序列测定表明,该菌株与弧菌属中几株病原菌的同源性均达到98.9%以上。在分子进化树中该菌株与副溶血弧菌Vibrio parahaemolyticus的进化地位最接近。综合上述实验结果分析得出,该细菌分离物为副溶血弧菌。

Isolation, identification, and pathogenicity analysis of a Vibrio parahaemolyticus strain from Litopenaeus vannamei

A pathogenic bacterium strain 20100612001 was isolated from the hepatopancreas tissue of diseased white shrimp Litopenaeus vannamei. The LD50 challenge assay was performed and the LD50 value was found to be 1.44×106CFU/ml. The cell morphotype was observed to be bacilli,coccoid rod or pear-like and some cells could be observed intensely stained at two poles. The strain was Gram-negative, sporeless and had a single polar flagellum. It formed transparent or translucent round colonies on 2216E solid medium but green or blue-green colonies on TCBS medium. It showed the highest identity to V. parahaemolyticus or Vibrio natriegenis by using fatty acid analysis and Biolog system. Based on 16S rRNA sequencing,the strain is >98.9% identical to several species in Vibrio genus, and the phylogenetic tree revealed that it is most close to Vibrio parahaemolyticus. Taken together, the pathogenic strain 2010060612001 is identified as V. parahaemolyticus.