一株肉牛源干燥棒状杆菌的分离鉴定

Isolation and Identification of a Strain of Corynebacterium xerosis from Beef Cattle

为了确定河北省昌黎县某肉牛场肉牛发病原因,本研究从呼吸道症状明显的病牛鼻粘液中分离纯化到1株优势菌,采用细菌培养、革兰氏染色、细菌生化鉴定、rpoB基因检测、16S rRNA序列分析方法鉴定,经K-B试纸法检测该分离菌对泰乐菌素、头孢拉定等18种抗生素的药物敏感性。结果显示,分离菌革兰氏染色呈阳性短杆状球菌,在血琼脂培养基上可生长为干燥且粗糙的淡黄色菌落,在LB液体培养基中呈沉淀生长,菌液上层轻微浑浊,下层有颗粒状、片状沉淀;rpoB基因PCR扩增检测结果为阳性;该分离菌具有脂酶、赖氨酸脱羧酶、β-葡萄糖苷酶、α-葡萄糖苷酶活性,能够发酵海藻糖、麦芽糖、蔗糖,结果符合干燥棒状杆菌生化特性;16S rRNA序列比对分析表明,该分离菌与干燥棒状杆菌同源性为99%,一致性为91.6%;对泰乐菌素、头孢拉定等7种药物耐药,对环丙沙星、恩诺沙星等9种药物敏感。试验结果表明该分离菌为干燥棒状杆菌。

To determine the cause of the disease in beef cattle on a beef farm in Changli County,Hebei Province,a dominant strain was isolated and purified from the nasal mucus of diseased cattle with obvious respiratory symptoms,and identified by bacterial culture,Gram staining,bacterial biochemical identification,rpoB gene detection and 16S rRNA sequence analysis.The drug susceptibility of the isolate to 18 antibiotics such as tylosin and cefradine was tested by K-B test paper.The test results showed that the isolate was positive for Gram staining of short rod-shaped cocci,and could grow as dry and rough yellowish colonies on blood agar medium,and precipitated in LB liquid medium,with slight turbidity in the upper layer and granular and flaky precipitation in the lower layer.The isolate was identified as having lipase,lysine decarboxylase,β-glucosidase andα-glucosidase activities,and was able to ferment algose,maltose and sucrose,which were consistent with the biochemical characteristics of Corynebacterium xerosis.The homology and consistency of 16S rRNA sequences with Corynebacterium saudium were 99%and 91.6%.It was resistant to seven drugs,such as Tylomycin and cefradine,and sensitive to nine drugs,such as ciprofloxacin and Ennoxacin.The test results show that the isolate is Corynebacterium xerosis.