Preparation of Chromobacterium Inactivated Vaccine and Evaluation of Its Immune Effect

In order to prevent and control the Chromobacterium infection in red pandas, according to the preparation procedure of bacterial inactivated vaccine, two strains of Chromobacterium CV08 strain and CV20 virulent strain isolated from Straits (Fuzhou) Giant Panda Research and Exchange Center in 2008 and 2020 were inactivated after the optimization of conditions, and then the inactivated bacteria solution was prepared by combining with the aluminum-containing adjuvants to produce the inactivated vaccine. The BALB/c mice were used as the experimental animals to establish a model of Chromobacterium infection. The inactivated vaccine of CV20 virulent strain was inoculated in two ways to compare the effects of the two inoculation routes. The median lethal dose (LD₅₀) gradient of two strains of Chromobacterium was further designed to carry out the challenge protection test on mice after the secondary immunization, and the cross-challenge protection test was also carried out. The results showed that the effect of intramuscular injection with the inactivated vaccine of CV20 virulent strain was better than that of subcutaneous injection. The LD₅₀ of CV08 virulent strain and CV20 virulent strain to each mouse was 3.2×10⁸ and 5×10⁷ CFU, respectively. The protective rates of the inactivated vaccine of Chromobacterium CV08 virulent strain on the mice challenged with different LD₅₀ were 83%, 70% and 60%, respectively, while the protective rates of the inactivated vaccine of Chromobacterium CV20 virulent strain on the mice challenged with different LD₅₀ were 75%, 70% and 10%, respectively. The bacterial contents of CV08 and CV20 virulent strain vaccines prepared in the experiment were both 4×10⁹ CFU·mL^-1, which passed the safety test and could produce better protective effect against the infection of their own strains but had no cross-protective effect.