凡隆气单胞菌在人工感染斑点叉尾鮰体内的动态分布

Dynamic distribution of Aeromonas veronii in Ictalurus punctatus

为研究凡隆气单胞菌在人工感染斑点叉尾鮰体内的动态分布规律及其致病机理,用凡隆气单胞菌(8×107 CFU/mL)分别以浸泡和腹腔注射的方式感染斑点叉尾鮰,于接种后第1、2、6、12、24、48、72和96小时剖杀采样,制备石蜡切片,HE染色,镜检,并采用亲和免疫组织化学方法检测凡隆气单胞菌在斑点叉尾鮰体内的动态分布。结果显示,浸泡组在接种后第2小时,首先在鳃检测到阳性信号,6h后从脾和肾中检测到阳性信号,随后在肝和脑中也有少量阳性信号被检出;腹腔注射组在接种后第2小时即从脾和肾中检测到阳性信号,随后肝中也检测到阳性信号,而鳃中没有检测到阳性信号。两种感染方式阳性信号在各组织器官内的分布相似,主要出现在肾、脾和肝的吞噬细胞内、血管内、坏死区域、细胞间质区域以及少量实质细胞内,引起多器官的充血、出血、全身性炎症及变性和坏死,并随着感染时间的延长,检出量逐渐增多,肌肉、心脏、肠和眼球组织中没有检测到阳性信号。结果表明,凡隆气单胞菌感染途径多样化,自然环境中可通过鳃进入斑点叉尾鮰机体,肝、肾、脾是主要的感染靶器官,靶器官的损伤是造成斑点叉尾鮰死亡的重要原因之一。

Channel catfish(Ictalurus punctatus)were inoculated intraperitoneally with Aeromonas veronii JF490063strain at 0.1mL/tail or immersed in water with concentration of bacteria at 8×107 CFU/mL, respectively,then were slaughtered at 1h,2h,6h,12h,24h,48h,72hand 96hafter inoculation.Tissues were processed to prepare for paraffin sections,and stained using haematoxylin and eosin,and immunohistochemistry to determine pathogens.In the immersed-in-water group,positive signals appeared firstly in the gill at 2h,then in the kidney and spleen at 6h,seldom positive signals in the liver and brain.In the intraperitoneally-inoculated group,positive signals appeared firstly in the kidney and spleen at 2h,then in the liver,and no positive signals were observed in the gill.Immunohistochemistry still showed a similar distribution between two groups,and positive signals mainly scattered in phagocytic cells,blood,necrotic zone, interstitial cells and parenchyma such as parenchyma,caused systemic inflammation,organs denaturation and necrosis,and no signals were present in the skin,muscle,the heart,intestinal and eyes.The results showed that the infection route was diversified,A.veronii JF490063through the gill into the in natural environment,and the kidney,spleen and liver were the main targets during infection.These targets may underlie the pathogenesis of the naturally occurring disease.