1株温和性噬菌体的发现及其流行病学意义

Identification and epidemiological significance on lysogenic phage L128m

目的对云南省野鼠鼠疫疫源地齐氏姬鼠盲肠内容物中分离的1株鼠疫噬菌体(L128m)进行鉴定,探讨鼠疫自然疫源地微生态因素保存鼠疫自然疫源性发挥的作用。方法以鼠疫疫苗株EV 76为宿主菌,采用双层琼脂平皿法从云南省鼠疫疫源地齐氏姬鼠盲肠中分离1株温和噬菌体;描述其形态特征;测定裂解能力、宿主谱。结果鼠疫噬菌体L128m形成的噬菌斑中心和边缘均模糊,直径为0.9~1.0 mm,其为溶原性噬菌体;通过液体增殖培养后其效价达到106~P FU/ml;电镜观察其形态呈蝌蚪形,头部为正多面体结构,头部直径约为61 nm,尾部长约155 nm,带有一伸缩的尾鞘,归类为肌尾噬菌体。宿主谱评价发现仅裂解鼠疫疫苗株。结论从1只齐氏姬鼠盲肠内容物中分离的鼠疫噬菌体属溶原性噬菌体,它的发现对我国鼠疫疫源地宿主动物肠道微生态学和流行病学研究具有重要意义。

Objective To isolate and identify the characteristics of Yersinia pestis phage L128m from the cecum of Apodemus chevriert in Yunnan plague focus,and probine into ecological factors in plague focus playing the role. Methods Phage L128m was isolated from Yunnan plague focus by double-layer agar plate method with attenuated vaccine Yersinia pestis strain EV 76 as the host bacterium. Phage particle was observed under the electron microscope while biological properties of phage L128m including lytic capacity and host spectrum were identified. Results The plaque of phage L128m was about 0. 9 -1. 0 mm in diameter with rough edge and non-transparent centre,it belongs to lysogenic phage. It titer could reach to 10~6 PFU/ml after propagated. The particles of phage L128m presented tadpoles-like features,with an icosahedra head of about 61 nm in diameter and a contractile tail structure of about 155 nm. It belongs to the order Caudovirales and family Myoviridae. The phage presented special lysic ability to Yersinia pestis. Conclusion Lysogenic phage L128m was isolated from the cecum of Apodemus chevriert in Yunnan plague natural focus. Our findings related to narrow host spectrum and less poorer Lysis activities. It may play an important role on epidemiological significance and intestinal microecology of animals in plague natural focus.