Biological Characteristics And Pathogenic Gene Detection Of Bovine Serotype A Pasteurella Multocida

In this study,the biological characteristics and pathogenic characteristics of a bovine Pasteurella multocida isolated in the field were studied.Morphological observation,16S rRNA and specific primer PCR were used to identify the strains of Pasteurella multocida,and the serotype was detected by PCR,which is to understand the classification characteristics of the strain.The drug resistance and LD ₅₀ were determined by disc agar diffusion method and animal inoculation.The distribution of the common virulence genes in the Pasteurella multocida was measured by PCR,and the histopathological observation of the inoculated animals was carried out.The relationship between the virulence gene and the disease was analyzed,and the basic information was provided for the revelation of the pathogenic mechanism.The experimental results show that:1.The isolates were Pasteurella multocida serotype A.2.The median lethal dose,LD ₅₀ of isolated bacteria was 25.85 CFU/mL,which was strong virulence strain.The isolates were resistant to clindamycin,neomycin,penicillin,sulfaisoxazole and teicoplanin,and were moderately sensitive to clarithromycin and erythromycin,and were sensitive to the other 25 antibiotics.3.The pathological results showed that the main pathological changes were alveolar hyperemia,inflammatory exudation,spleen lymphocyte decrease and macrophage increase,and hepatocyte and renal tubular epithelial cell necrosis.4.The distribution of virulence genes of the isolates was measured and 7 kinds of 23common virulence genes were detected.Among them,19 virulence genes were detected in6 major categories,including the adhesion factor gene?ptfA,fimA,hsf-2,pfhA,tadD?,the iron uptake gene?exbB,exbD,tonB,hgbA,Fur?,the sialic acid gene?nanH?,hyaluronidase gene?pmHAS?,outer membrane protein gene?ompA,ompH,oma87,plpB?and superoxide dismutase gene?sodA,sodC,tbpA?.