|
From 14 isolated strains Pasteurella multicida, two strains which producted dermonecrotic toxin ( DNT ) were selected. As the bacteria cultured in brain heart infusion adding 5 % serum plus for 20 hours , the harvest was sonicated for DNT. After the protein contain of toxin was determinated, the protein concentration was adjusted to 1 mg per milliliter. The minimal necrotizing dose of rough DNT was about 3 µg of protein. The purified DNT from column chromatography could produce dermonecrotic reaction on guinea pig by 6 ng of protein.
Rough DNT toxin was inactived with formaldehyde. Toxoid added inactived pasteurella cell suspension was mixed with alum gel adjuvant to form toxoid vaccines.Mouse vaccinated twice with the toxoid vaccines appeared 1. 75 to 1.93 log folds of protected potency to the challenge of pathogenic Pasteurella cell suspension.Guinea pigs that had two times immuned with toxoid vaccines showed 75 to 100 % protected potency to LD50 bacterial suspension challenge.
Pregnant sows at 3 ~ 5 weeks prior farrowing and piglets at 1 to 3 weeks of age were mmuned twice with toxoid vaccines at an interval of 2~ 3 weeks showed completed safety and resulted in protecting the baby pigs and piglets to the challenged at 5 weeks old.
|