鲫鱼类志贺邻单胞菌的鉴定及其致病机制研究

Identification and pathologic mechanism of Plesiomonas shigelloides isolated from Carassiusauratus

为了鉴定从患病鲫鱼体内分离的F01菌株并探究其致病性,本研究经形态学观察、16S rDNA基因分析鉴定F01菌株,并进行药敏试验,采用动物回归试验及病理组织学观察研究其对鲫鱼的致病性,同时检测感染鲫鱼的血清学指标及免疫因子表达。结果显示:F01菌株经16S rDNA基因序列比对与类志贺邻单胞菌的同源性达99%,确定该菌株为类志贺邻单胞菌,其对鲫鱼的半数致死量LD50为2.09×107 cfu/mL,且动物回归实验结果显示从人工感染鲫鱼分离出的细菌与患病鲫鱼一致。耐药性检测结果显示,该菌株对头孢曲松、头孢呋辛、氧氟沙星等敏感,对哌拉西林、克林霉素、多西环素等耐药。病理组织学观察显示,感染鲫鱼的肝、肾等组织充血、肿胀、变性坏死。血清学检测结果显示,与对照组比较,感染组鲫鱼血清AKP、LZM均活性上升、MDA活力均下降(p<0.05);免疫因子检测结果显示,感染10 d后鲫鱼脾脏中HSP70、IL-8、TLR22基因的转录水平显著高于正常对照组(p<0.05)。本研究通过对F01菌株的致病性等研究,为深入研究类志贺邻单胞菌的疫病防治提供科学参考。

To identify the strain F01 isolated from diseased Carassiusauratus and verify its pathogenicity,we carried out the morphology observation,16s rDNA PCR amplification,and examination of its drug sensitivity.The pathogenicity of the strain F01 were tested by recursive infection experiment and histopathology.Simultaneously,the serological indexs and immune factor were detected.The results showed that strain F01 shares 99% homology with Plesiomonas shigelloides in alignments of 16S rDNA,therefore identified as Plesiomonas shigelloides,its half lethal dose LD50 was 2.09×107 cfu/mL.The bacteria recovered from artificially infected fish were identical to that isolated from the diseased fish.Strain F01 was sensitive to ceftriaxone,cefuroxime and ofloxacin,and resistant to piperacillin,clindamycin and doxycycline.Histopathological observation showed that the liver,kidney and other tissues were congested,swelling,degeneration and necrosis.The serum index analysis showed that compared with the control group,the activities of AKP,LZM were significantly increased,and MDA were significantly decreased in the infected group(p<0.05).Transcription analysis of immune factors showed that the transcription levels of HSP70,IL-8 and TLR22 in the spleen of test groups were significantly higher than the control group at 10 days post-infection(p<0.05).The data collected from this study will provide a sight for better understanding of prevent and treatment of the disease caused by Plesiomonas shigelloides in Carassiusauratus.