Dynamic bacterial colonization and microscopic lesions in multiple organs of tilapia infected with low and high pathogenic Streptococcus agalactiae strains
Dynamic bacterial colonization and microscopic lesions in multiple organs of tilapia infected with low and high pathogenic Streptococcus agalactiae strains
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低致病性和高致病性无乳链球菌感染罗非鱼多个器官的动态细菌定植和显微病变
DOI：
10.1016/j.aquaculture.2017.01.013
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发表时间：
2017
期刊：
影响因子：
4.5
通讯作者：
Li Anxing
中科院分区：
文献类型：
--
作者：
Su Youlu;Feng Juan;Liu Chan;Li Wei;Xie Yundan;Li Anxing
无乳链球菌（又称GBS）是一种新兴的鱼类病原体，对罗非鱼具有致命性。然而，不同致病性GBS菌株之间病原体-宿主相互作用的差异尚不清楚。在本研究中，我们研究了低致病性TFJ0901和高致病性THN0901菌株感染罗非鱼的动态细菌定植和多器官的显微病变。通过qPCR检测，我们发现THN0901在感染早期很容易侵入脾脏，然后在大脑和眼睛中有效复制，而在tfj0901感染的鱼的所有组织中，细菌负荷在任何时间点都保持在恒定的较低水平。免疫组织化学和组织病理学均显示，两株菌株引起的显微病变的差异主要集中在血管/窦内，THN0901感染更容易导致内皮细胞内的退行性病变，继发血管病变和局部组织梗死，以脑、脾、肾和鳃为主。THN0901也可导致典型的组织病理学改变，包括脑膜炎、心外膜炎和肾肉芽肿。相比之下，随着时间的推移，TFJ0901在这些组织中引起轻微或没有显微镜病变。有趣的是，本研究提供了THN0901通过腹腔注射粘附并侵袭肠上皮细胞的直接证据。此外，脾脏的触摸印迹涂片也证实了THN0901可以在巨噬细胞中增殖并导致免疫细胞崩溃，而TFJ0901似乎没有这种能力。综上所述，我们在了解高致病性和低致病性GBS菌株之间病原体-宿主相互作用差异方面填补了空白，这将增强我们未来开发基于TFJ0901的减毒疫苗的能力。
Streptococcus agalactiae(also known as GBS) is an emerging pathogen of fish and is fatal to tilapia worldwide. However, the differences in pathogens-host interactions among different pathogenic GBS strains remain unclear. In this study, we investigated the dynamic bacterial colonization as well as microscopic lesions in multiple organs of tilapia infected with the low pathogenic TFJ0901 and high pathogenic THN0901 strains. Using the qPCR assay, we revealed that THN0901 can easily invade the spleen at the early stage of infection, and then effectively replicate in the brain and eyes, while bacterial loads are maintained at constant lower levels in all tissues of TFJ0901-infected fish at any time points. Both immunohistochemistry and histopathology showed that the differences in the microscopic lesions caused by the two strains were mainly focused on the blood vessels/sinusoids, and that THN0901 infection was more likely to lead to degenerative lesions within the endothelial cells, with subsequent vascular lesions and local tissue infarction, particularly in the brain, spleen, kidney and gills. THN0901 can also result in typical histopathological changes, including meningitis, epicarditis, and renal granuloma. In contrast, TFJ0901 caused slight or no microscopic lesions in those tissues over time. Interestingly, this study provides direct evidence that THN0901 can adhere to and invade the intestinal epithelial cells through intraperitoneal injection. Furthermore, touch impression smears of the spleen also confirmed that THN0901 can proliferate in macrophages and cause immune cells to collapse, whereas TFJ0901 did not appear to have the ability to do so. In summary, we closed a gap in understanding the differences in pathogen-host interactions between high and low pathogenic GBS strains, which will enhance our ability to develop an attenuated vaccine based on TFJ0901 in the future.