Aeromonas hydrophila is a common pathogenic bacterium that causes motile Aeromonas septicaemia (MAS), but the pathogenic mechanism of this species remains unclear. In the present study, histological and ultrastructural alterations of the trunk kidney, head kidney, spleen and liver in Myxocyprinus asiaticus experimentally infected with virulent A. hydrophila (vAh) were analysed. Histopathological observations showed damaged endothelial cell, haemolysis, melano-macrophage centre (MMC) response, necrosis, lymphocyte infiltration, vacuolization, concretion and acidophilic degeneration of hepatocytes and erythrocyte atrophy degeneration, etc. Notably, the strategy of MMC response indicated that the spleen plays a dominant role in the immune response. Ultrastructural pathological features of MAS showed collapsed blood capillary, mesangial cell swelling, podocyte hyperplasia, structure destruction of the glomerular filtration device. Severely damaged Disse space of liver, disappeared glycogen, swelling mitochondria, increased autophagic lysosomes in hepatocytes were also observed in infected juveniles. In conclusion, these results indicated that vAh infection would lead to serious pathological changes in tissues, which maybe in turn results in death from anoxia, energy shortage and metabolic waste accumulation. But meanwhile, MMC played an important role in immune response, which could represent a new tool for diagnosis of MAS and for gaining novel insight into some aspects of disease pathogenesis.

中文翻译：

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嗜水气单胞菌急性感染粘液鱼的组织病理学和超微结构变化特征

嗜水气单胞菌是一种常见的致病菌，可引起运动性气单胞菌败血症（MAS），但该物种的致病机制尚不清楚。在本研究中，实验感染了毒力A 的粘液鱼，其躯干肾、头肾、脾脏和肝脏的组织学和超微结构改变。 嗜水菌(vAh) 进行了分析。组织病理学观察显示内皮细胞受损、溶血、黑色素巨噬细胞中心（MMC）反应、坏死、淋巴细胞浸润、空泡化、肝细胞凝固和嗜酸性变性、红细胞萎缩变性等。 值得注意的是，MMC反应策略表明脾在发挥作用在免疫反应中起主导作用。MAS超微结构病理表现为毛细血管塌陷、系膜细胞肿胀、足细胞增生、肾小球滤过装置结构破坏。在受感染的幼鱼中还观察到肝脏Disse间隙严重受损，糖原消失，线粒体肿胀，肝细胞自噬溶酶体增加。综上所述，这些结果表明，vAh 感染会导致组织发生严重的病理变化，进而可能导致缺氧死亡、能量短缺和代谢废物积累。但与此同时，MMC 在免疫反应中发挥了重要作用，这可能代表了诊断 MAS 和获得对疾病发病机制某些方面的新见解的新工具。