Model Of Zebraflsh Infected By Fusobacterium Necrophorum And Immune Protective Trial

Fusobacterium necrophorum （FN）is a primary or secondary pathogen,which infected animals andhumans to produce various necrotic and suppurative disease. It exists in nature widely. Liverabscesses and foot rot affect the production performance of livestock seriously,bring a huge loss to thebreeding industry. We take the pathogenic FN(AB) as the research object, screening suitable mediumfor the growth of FN(AB), established the Fusobacterium necrophorum-zebrafish infection model byhistopathological and molecular biology method, and used the model to conduct a preliminaryexploration for the antigens protection of FN.(1) Medium screening test: We found that brain heart infusion medium(BHI) was the suitablemedium for FN(AB) among the three kinds of medium which used commonly. We studied the growthcycle of FN(AB) in BHI by spectrophotometer and bacteria counts, and the lag phase from0to12h,12h~24h was the logarithmic growth phase, after24h the bacterium got into the stable and thedecline phase.(2) Zebrafish inflectional test: healthy wild zebrafish were chosed, and10μL of the bacterialsuspension were injected in intraperitioneal and cultivation in aquarium tank at29±1℃,then, have acontinuous observation for seven days and record the circumstances of death. According to the methodof Reed-munch, LD50is1.06×106cfu.After12h,zebrafish appeared lesions and die-off. We canobserved yellowish ascites, intestinal slight bleeding, liver enlargement after open the body cavity.Histopathological examination revealed that liver and kidney degeneration and necrosis, intestinalmucosa shedding.We have isolated the pathogenic strains from the diseased tissue. Zebrafish is asuitable animal model to the reserch of Fusobacterium necrophorum.(3) Protection test of zebrafish resistance to FN (AB) infection: healthy wild zebrafish wereselectedand were injected ip with10μL cracking antigen and antiserum that against FN respectively.Control group were given the same dosage of saline. Zebrafish were given a boost doage after7days. On day28,50LD50dose of FN (AB) were injected i.p in zebrafish. The control group all died,while the relative survival percent(RSP) in cracking antigen of FN group and antiserum of against FNgroup was44%and46.7%respectively. It revealed that cracking antigen and antiserum in zebrafish hasa protective effect.