Study on Toxicity of Natural Leukotoxin of Pathogenic Fusobacterium necrophorum

In order to study the toxicity and pathogenic mechanism of leukotoxin of high pathogenic Fusobacterium necrophorum),cytotoxicity test,microscopic observation and transmission electron microscope(TEM) were used to evaluate the toxicity of leukotoxin isolated from the culture supernatant of F.necrophorum.The results indicated that natural leukotoxin of F.necrophorum exhibits a high cytotoxicity to the bovine peripheral leukocytes in a dose dependent manner.The toxin induces apotosis at low concentration,and lyses the cell at higher concentration.Moreover,the natural leukotoxin can also induce necrosis lesions at the injecting site and protect the animal against experimental challenge with F.necrophorum.This study has laid theoretical foundation for understanding pathogenic mechanism of leukotoxin of F.necrophorum.