1株鸡源鸭疫里默氏杆菌的分离鉴定及其生物学特性分析

Isolation,Identifi cation and Biological Characterization of a Riemerella anatipestifer Strain from Chicken

为了解鸡源鸭疫里默氏杆菌(RA)的致病性,对1株2021年从病鸡肝脏中分离的RA疑似菌株进行染色镜检、生化鉴定、血清型鉴定、药敏试验、动物致病性试验及病理学观察并分析其16S rRNA序列。结果显示:菌株不发酵糖类,脲酶试验、触酶试验、氧化酶还原试验、明胶液化试验和枸橼酸盐试验均为阳性,硫化氢、VP、MR试验均为阴性;血清型鉴定为血清10型;分离菌对氨苄西林、阿莫西林、头孢噻呋、环丙沙星、磺胺异噁唑、红霉素、多西环素、氟苯尼考高敏,对头孢曲松、恩诺沙星、大观霉素、庆大霉素耐药;动物试验表明,能引起鸭和鸡的“三炎”症状,对鸭具有高致死率且能导致鸡出现严重关节软组织病变;病理学变化显示人工感染鸡心外膜增厚,充满纤维蛋白,炎性细胞浸润,主要炎性细胞为淋巴细胞;肝脏局灶性炎性细胞浸润,主要为淋巴细胞,部分肝细胞出现胞浆和核深染的固缩现象;脾脏血管周围有少量淋巴细胞浸润;腿部组织中充满渗出液,大量炎性细胞浸润于血管周围。16S rRNA序列比对显示分离株与GenBank RA参考株同源性均在99%以上,确认其为RA。遗传进化分析显示分离株与当前毒力最强的RA Hxb2株高度同源。本试验证明鸡源RA QD01株对鸡和鸭都具有强致病性并能在鸡群中流行传播。

In order to understand the pathogenicity of Riemerella anatipestifer of chicken origin,a suspected strain isolated in 2021 from a diseased chicken liver was examined by staining microscopy,biochemical reactions,serotyping,drug susceptibility test,animal pathogenicity and 16S rRNA sequencing.This strain did not ferment sugars and produced positive results in urease,catalase,oxidase reduction,citrate utilization and gelatin liquefaction testings but negative reactions for sulfide,VP and MR testings.Serotyping demonstrated it was serotype 10.This strain was highly susceptible to ampicillin,amoxicillin,ceftiofur,ciprofloxacin,sulfamethoxazole,erythromycin,doxycycline and florfenicol and resistant to ceftriaxone,enrofloxacin,spectinomycin and gentamicin.Animal tests showed that it caused"three inflammatory"signs in ducks and chickens with high mortality in ducks and severe joint and soft tissue lesions in chickens.Pathological examinations showed that the infected chicken had thick epicardium with full fibrins,inflammatory cell infiltration with mainly lymphocytes.Other pathological changes included focal inflammatory cell infiltration in livers with mainly lymphocytes,deep stained pyknosis of cytoplasm and nucleus in some hepatocytes,a small amount of lymphocyte infiltration around the blood vessels of spleens,exudate in leg tissues and a large number of inflammatory cells around the blood vessels.Alignment of 16S rRNA sequences showed that the homology between this strain and other GenBank reference strains was more than 99%,confirming it was R.anatipestifer.Genetic evolution analysis showed that this strain was highly homologous to the most virulent R.anatipestifer Hxb2 strain isolated from Shanghai Veterinary Research Institute.This experiment proved that the chicken-derived R.anatipestifer QD01 strain had strong pathogenicity to chickens and ducks.