犊牛大肠杆菌噬菌体的分离、生物活性分析及初步应用研究OA

In order to screen phages that show a strong lytic effect and a broad host range against bovine Escherichia coli,a strain of E.coli(designated EN8)was isolated from diarrheic calf feces at a cattle farm in Baoding,Hebei Province.Using E.coli EN8 as the host strain,a bacteriophage(vB_EcoM-EN8)was isolated via the double-layer agar plate method.Its morphology was characterized by electron microscopy,and its lytic spectrum,temperature and pH stability,optimal multiplicity of infection(MOI),and growth kinetics were investigated.Preliminary in vitro application studies were also conducted.Results showed that phage vB_EcoM-EN8 had a head-tail structure under electron microscopy,featuring a unique icosahedral head(90 nm in diameter)and a tail(130 nm in length).This classifies it within the order Caudovirales and family Myoviridae.The phage demonstrated broad host specificity,effectively lysing 19 bovine-derived E.coli strains from clinical isolates,7 murine-derived strains,and 1 avian-derived strain,achieving a lytic rate of 27/48(≈56％).In vitro,vB_EcoM-EN8 effectively suppressed E.coli growth across varying MOIs and exhibited tolerance to pH 6.0～10.0 and temperatures of 4～50℃while maintaining high activity.Its optimal MOI was determined as 0.001,with a latent period of 20 min,lytic period of 90 min,and burst size of 422 PFU/cell.Furthermore,vB_EcoM-EN8 demonstrated robust environmental tolerance,stability,and lytic efficiency,providing a technical foundation for developing phage-based therapeutics against calf colibacillosis.