奶牛乳房炎源链球菌裂解噬菌体的分离鉴定

Isolation and Characterization of a Streptococcus Bacteriophage from Bovine Mastitis

奶牛乳房炎对奶牛产业的影响严重,传统抗菌疗法面临细菌耐药和药物残留的问题,因此急需研发一种能解决现有抗菌药物弊端与危害的新型疗法。论文以奶牛乳房炎源链球菌为宿主菌,分离获得裂解性噬菌体,对其进行生物学特性分析,为奶牛乳房炎无抗防治提供生物学材料。试验采用常规方法分离、纯化噬菌体,通过双层琼脂平板法观察噬菌斑的形态并测定其生物学特性,在透射电镜下观察噬菌体的形态特征。结果显示,分离出一株裂解性链球菌噬菌体,将其命名为SM-P21,噬菌斑呈无色透明的圆形,SM-P21头部为20面体,呈蝌蚪形,具有尾鞘等结构,核酸类型为双链DNA。噬菌谱检测结果显示,该噬菌体只对宿主菌株具备裂解能力而对其他菌株无裂解能力。SM-P21的最佳感染复数为10、潜伏期约15 min、暴发期为95 min、裂解量约为249 PFU/cell。在60℃环境下,SM-P21滴度大幅度下降。SM-P21对pH的耐受范围较广,在pH 4.0~11.0之间其活性没有明显下降。说明噬菌体SM-P21裂解性能较强,适应性好,具有很好的应用前景。

The dairy cow mastitis has serious impact on the dairy industry,and traditional antibacterial therapies face the problems of bacterial resistance and drug residues.Therefore,there is an urgent need to develop a new type of therapy that can solve the drawbacks and harms of antibacterial drugs.It is proposed to use Streptococcus mastitis-derived in dairy cows as the host bacteria to isolate and obtain lytic phages and analyze their biological characteristics,so as to provide biological materials for the prevention and treatment of dairy cow mastitis.In the experiment,conventional methods were used to isolate and purify the phage,the morphology of the plaque was observed by the double-layer agar plate method and the biological characteristics were measured,and the morphological characteristics of the phage were observed under the transmission electron microscope.The experiments showed that we isolated a lytic Streptococcus phage,it is named as SM-P21 and the phage plaque exhibits a colorless and transparent circle.The SM-P21 head is a twentieth body which structure is a tadpole shape.The nucleic acid type is double-stranded DNA.The results of phage analysis showed that it could only lyse the host strain,but not other strains.The maximal infection number of SM-P21 is 10,the incubation period is 15 min,the outbreak period is 95 min,the lysis is about 249 PFU/cell.At temperature 60℃,SM-P21’s titer declines.SM-P21 has a wide range of tolerance to pH,and there was no significant decrease in the activity between pH 4.0 and 11.0.The results indicated that the phage SM-P21 has strong lysis performance,good adaptability and good application value.