鹅大肠埃希菌的分离鉴定及系统进化树分析

为对发病鹅感染致病性大肠埃希菌的临床治疗提供指导并防控致病性大肠埃希菌感染，本研究无菌采集腹泻鹅及病死鹅脾脏、肝脏等组织器官进行病原菌分离培养、染色观察、生化鉴定、致病性试验，对菌株部分基因进行测序、构建遗传进化树并进行药敏试验。结果显示，普通琼脂培养基上生长出灰白色、圆形、凸起、边缘整齐菌落，麦康凯琼脂培养基上长出玫红色、光滑圆润菌落；分离菌株经革兰氏染色，镜下可见革兰氏阴性菌，两端钝圆、大小中等，多呈单个存在的杆状菌；致病性试验表明，该分离菌株对小鼠、雏鹅均有较高致死率；遗传进化树结果显示，分离菌株与患者粪便分离株（GenBank登录号：CP024992.1）同源性最高，达99.5%；体外抑菌试验发现菌株耐药情况较严重，对大多数抗菌药均有较强抗性，仅头孢噻呋对该分离株有较强的抑菌作用，合理用药后病情得到有效控制。本研究为有效防治鹅大肠埃希菌病提供了理论依据，对规模化鹅场防控大肠埃希菌等其他细菌性疾病具有重要价值。

Isolation,Identification and Phylogenetic Tree Analysis of Goose E. coli

In order to provide guidance on the clinical treatment of pathogenic E. coli infection in morbid geese and to prevent and control pathogenic E. coli infection,in this study,spleen,liver and other tissues and organs of diarrhea geese and dead geese were collected aseptically for pathogen isolation and culture,staining observation,biochemical identification,pathogenicity test,partial gene sequencing,phylogenetic tree construction and drug sensitivity test.The results showed that off-white,round,raised,and neatly edged colonies grew on ordinary agar medium,and rose-red,smooth and round colonies grew on MacConkey agar medium.Gram negative bacteria were observed under microscope after Gram staining,the two ends were obtuse and medium in size,most of them were rod-shaped bacteria.The pathogenicity test showed that the isolated strain had high mortality to mice and goslings.The results of the phylogenetic tree showed that the isolated strain had the highest homology with the patient fecal isolate (GenBank accession No.:CP024992.1),reaching 99.5%.In vitro antibacterial test showed that the drug resistance of the strain was serious,and it had strong resistance to most antibiotics.Only ceftiofur had strong antibacterial effect on the isolated strain,and the disease was effectively controlled after rational drug use.This study provided a theoretical basis for the effective control of E.coli in geese,and had important value for the prevention and control of E.coli and other bacterial diseases in large-scale goose farms.