罗氏沼虾源维氏气单胞菌的分离鉴定、毒力基因检测及组织病理学观察

为鉴定江苏省高邮市某养殖场罗氏沼虾(Macrobrachium rosenbergii)发病死亡的病原体,研究从患病濒死的罗氏沼虾肝胰腺中分离出一株优势菌WSQ-1,对其进行纯化培养、革兰氏染色、生理生化特征鉴定、16S rRNA及gyrB基因序列分析,鉴定为维氏气单胞菌(Aeromonas veronii)。回归感染实验表明,分离株WSQ-1对罗氏沼虾有较强致病性,且出现与自然发病类似的症状:感染虾活力减弱,食欲下降,肌肉发白; 72h半致死浓度(LD50)为2.51×10⁶ CFU/mL。组织病理学观察可见其肝胰腺组织病理损伤,并随感染浓度的增加或感染持续时间的延长而逐渐加重:低浓度或感染前期结缔组织间隙增大并积聚少量炎性细胞;继而肝小管管腔变形,肝细胞空泡化,部分组织坏死;高浓度或感染后期肝小管及结缔组织大面积坏死导致不可逆损伤。毒力基因检测显示该菌携带Acsv、AexT、Act、Aer、GcaT、Acg和OmpAI共7个毒力基因,表明分离菌具有较强致病性。药敏试验显示,该分离菌对头孢哌酮等16种药物敏感,对克拉霉素等10种药物耐药,仅对卡那霉素表现为中度敏...

ISOLATION,IDENTIFICATION AND VIRULENCE GENE ANALYSIS OF PATHOGENIC AEROMONAS VERONII IN MACROBRACHIUM ROSENBERGII AND ITS HISTOPATHOLOGICAL OBSERVATION

To identify the causative agent causing the death of adult Macrobrachium rosenbergii occurred in a cultured farm of Gaoyou city, Jiangsu Province, a dominant strain named WSQ-1 was isolated from the hepatopantras of dying M. rosenbergii and identified as Aeromonas veronii based on morphological observation, physiology characteristics, biochemical identification and sequencing of 16S rRNA and gyrB gene. The symptoms of M. rosenbergii artificially infected with the strain WSQ-1 were similar with those of natural infected M. rosenbergii, showing weakened vitality, decreased appetite and white muscle. The LD₅₀ to M. rosenbergii was 2.51×106 CFU/mL at 72h post infection. Histopathological observation showed that the pathological damage of hepatopancreas tissue was gradually aggravated with the increase of concentration or the duration of infection: the connective tissue space was enlarged and a small amount of inflammatory cells were accumulated in the early stage or low concentration, and then the lumen of hepatic tubule was deformed, hepatocytes were vacuolized, and some tissues were necrotic. In the late stage or high concentration, large area necrosis of hepatic tubule and connective tissue led to irreversible damage. The amplification result of virulence gene showed that the WSQ-1 carried 7 virulence genes including Acsv, AexT, Act, Aer, GcaT, Acg and OmpAI, which further indicated that the WSQ-1 had high virulence. Drug susceptibility test showed that 18 kinds of drugs such as cefoperazone had the most inhibitive effects on the strain. At the same time, it showed resistance to 11 kinds of drugs such as clarithromycin, completely resistant to 4 kinds of drugs such as penicillin G, only moderately sensitive to kanamycin. The results of this study can provide some reference for the identification of the pathogen of the bacterial disease of M. rosenbergii and the prevention and control of the disease caused by A. veronii.