Isolation And Identification Of Sheep Capsular Serotype A Pasteurella Multocida And Its Characterization

One of the susceptible animals of Pasteurella multocida(Pm)is sheep.In this project,nine large-scale farms in Hami,Changji,Altay,Hotan and Kashi regions of Xinjiang,China,The suspected disease material collected was used to isolate Pasteurella multocida for preliminary identification of the pathogen.The isolates were identified with biochemical reaction identification,PCR technology of Pm-specific genes and five serotype genes;We explored its biological characteristics by measuring the growth curve of one of the isolates,analyzing the drug resistance of the strains,attacking BALB/c mice with different injection routes,and animal regression experiment;Mice were immunized with the isolated strains,to understand their homologous and heterologous immune protection.The result of the investigation is that the average positive detection rate of Pasteurella multocida in some areas of Xinjiang is 34.8%(87/268).Bacteria isolated from the lung tissues of sick sheep grow smooth,moist slightly convex gray colonies on BHI agar medium.Gram-negative(red)Brevibacterium parvum,occasionally intensely stained;Isolates can ferment glucose,fructose and mannitol,catalase and indole reactions are positive.The 16S rRNA gene was successfully amplified,and the nucleotide sequence homology with Pasteurella multocida is greater than 99.7%.Pm species-specific genes and serotype identification results showed that Fragments of Pm species(460 bp)and Capsule A(1,045 bp)were amplified to match the size of Pasteurella multocida and Capsular serotype A.A total of 9 strains of Pasteurella multocida Serotype A were isolated.The drug sensitivity test of the isolate PmA-XJ1 showed that it was sensitive to florfenicol,cefradine,gentamicin and other drugs,and the number of viable bacteria was 1.2×108 cfu/mL.Mice and rabbits were injected with 1.2×107 CFU and 2.4×107 CFU respectively,and lambs were injected with 3.6×108 CFU of pure culture,and all animals died within 24 hours;Oral and nasal routes are ineffective for challenged mice,both subcutaneous and intraperitoneal injection can cause death.The vaccine was immunized subcutaneously on the back of the mice by 1 mL per mouse,and the protective effect of the aluminum hydroxide adjuvant vaccine on the same serotype of the isolate could reach 100%.The protection rates of the different serotypes of D,F and unknown types are;20%,20%,0.In this study,There occurred infection of Pasteurella multocida in large scale sheep farms in parts of Xinjiang.A total of 9 strains of Pasteurella multocida of sheep origin were isolated.The isolate PmA-XJ1 is highly toxic and highly pathogenic to a variety of laboratory animals.PmA-XJ1 was made into serotype A Pasteurella multocida aluminum hydroxide adjuvant vaccine,but its cross protection is not good.This study provides a theoretical basis for the later prevention and control of sheep Pasteurellosis and the more valuable vaccine of Pasteurellosis in Xinjiang.