生鲜乳中海氏肠球菌的分离鉴定

Isolation and Identification of Enterococcus hirae in Raw Milk

为了解生鲜乳中是否存在肠球菌污染,本试验从石河子某奶牛场无菌采集7份生鲜乳样品,通过细菌分离纯化、生化鉴定、16S rRNA和肠球菌RNA聚合酶α亚基(rpoA)编码基因的扩增和序列分析对分离菌株进行菌种鉴定,并利用纸片扩散法药敏试验和小鼠致病性试验确定分离菌株的药物敏感性和致病性。结果显示,从生鲜乳中分离到1株细菌,其培养特性和生化特性与肠球菌相似,16S rRNA基因测序结果显示其为肠球菌,rpoA基因测序结果显示其分子特征符合海氏肠球菌;药敏试验结果显示,分离海氏肠球菌对氨基糖苷类、林可胺类、磺胺类和多肽类药物表现一定的耐药性,而对四环素类、β-内酰胺类和部分喹诺酮类药物具有不同程度的敏感性;小鼠致病性试验结果显示,该菌株具有一定的致病性。本试验基于生鲜乳中海氏肠球菌的分离鉴定、耐药性和致病性分析,初步说明该牛场乳品中存在肠球菌污染的风险,且分离菌株具有一定耐药性和致病性,因此需在日常生产加工环节加强监测。

To investigate the presence of Enterococcus contamination in raw milk,seven raw milk samples were aseptically collected from a dairy farm in Shihezi.The bacterial isolates were identified through bacterial isolation and purification,biochemical identification,and sequence analysis of the 16S rRNA and RNA polymerase α subunit(rpoA) genes of Enterococcus.The antibiotic sensitivity and pathogenicity of the isolates were determined using the disk diffusion method and mouse pathogenicity test,respectively.The results showed that one bacterial strain was isolated from the raw milk.Its cultural and biochemical characteristics were similar to Enterococcus.The 16S rRNA gene sequencing indicated that the strain was Enterococcus,and the rpoA gene sequencing confirmed its molecular characteristics matched those of Enterococcus hirae.Antibiotic sensitivity tests revealed that the isolated Enterococcus hirae exhibited resistance to aminoglycosides,lincosamides,sulfonamides,and polypeptides,but was sensitive to varying degrees to tetracyclines,β-lactams,and some quinolones.Mouse pathogenicity tests indicated that the strain had a certain level of pathogenicity.This study,based on the isolation,identification,antibiotic resistance,and pathogenicity analysis of Enterococcus hirae in raw milk,preliminarily indicates the risk of Enterococcus contamination in the dairy farm's milk.The isolated strain poses certain antibiotic-resistant and pathogenic risks,emphasizing the need for enhanced monitoring during routine production and processing.