The Isolation And Identification Of Salmonella Pullorum Bacteriophage And Its Preliminary Application

The objective of this study was to isolate specific bacteriophage againsts S.Pullorum,to characterize it and to evaluate its lytic capacity against S.Pullorum in vitro and therapy effect in vivo.Firstly,we described the isolation and characterization of bacteriophage YSP2 able to specifically infect Salmonella,a member of the Siphoviridae family,is a temperate phage with a narrow host range,ashort latency(10 min) and a high bactericidal activity.The genomic length is about 30,000 bp.One-step growth curve reveales that the latent period of YSP2 is 10 min.YSP2 is thermostable,it still remained active after 40 min exposure at 80℃.Its optimal MOI is 0.001,andit is also stable atp H 4.0~12.0.In the phage application experiments, we established animal model of S.Pullorum infection by eye-drop and oral,respectively.By analysis of the LD50,we chose oral administration in the phage application experiments.Then the security detection experiment showed that phage YSP2 was so safty that none chicks had adverse reactions.Phage application experiments suggest that YSP2 concentration should be high to have significant S.Pullorum reductions in-vivo,and YSP2 should be given prior to pathogenic exposure in order to sustain that reduction over time.The highest therapeutic effect is the group that chicks took YSP2(1010 PFU/m L) and S.Pullorum simultaneously.When YSP2 were diluted to 108 PFU/m L,it also could maintain a high curative effect.In addition,necropsy results showed that YSP2 could effectively relieve chicks’ organic pathologic changes,especially the gastrointestinal hemorrhage.