Investigation Of Molecular Diagnostics And Drug Resistances Of Riemerella Anatipestifer

Riemerella anatipestifer mainly infect2~8weeks of ducklings, which caused the Infectiousserositis in ducks. The infection of Riemerella anatipestifer is one of the serious disease in theduck industry.21serotypes of Riemerella anatipestifer have been reported, little cross reactionwas found between different serotypes. At present, the prevention and treatment of Riemerellaanatipestifer mainly depends on drug, but the resistant strains increased with the application ofantibiotics. Therefore, this thesis provided a basis for prevention and treatment of Riemerellaanatipestifer by established molecular diagnostic method and performed for antimicrobial againstRiemerella anatipestifer isolated strains with disc diffusion assay.In this thesis,14strains were got from diseased Sheldrake on the plant of Hengfan, lin’an inZhejiang province by isolation、culture、physiological and biochemical identification.Based on theconserved region of16S rRNA gene sequence of Riemerella anatipestifer, the primers weredesigned andPCRtechnique was used for RA diagnosis of suspected cases. The results indicatedthat a698bp specific DNA fragment was amplified from6standard RA strains and14suspectedstrains, while no specific DNA fragment was detected from Escherichia coli and Salmonellaisolate. The homologous analysis showed99.9%similarity with RA in NCBI.PCRsensitivityexperiment was performed using standard RA liquid culture of different dilutions as templates andthe minimum detection value of2.3×10~3CFU/mL was obtained.Different tissues of10suspected ducks were tested by PCR, and the highest detection ratewas from the brain, then the heart blood, liver and the spleen in order, while no RA was detectedfrom the intestine and the muscle. The positive detection rate was90%and70%by PCR and bybacterial isolation method in order. The positive detection rate by PCR was higher than bacterialisolation method of20%. All these results indicated thatPCRmethod based on16S rRNA gene hasspecific, sensitive and fast properties for RA diagnosis and identificationSusceptibility testing was performed for9antibiotics and Coptidis rhizoma Decoction againstRiemerella anatipestifer isolated strains with disc diffusion assay. The results showed that thepathogens were highly sensitive to Coptidis rhizoma Decoction, Noroxin and Chlorampenicol, itssensitivity corresponding to100%,95%and90%; were sensitive to Tetracycline, Neomycin,Cephradine, its sensitivity corresponding to90%,85%and80%; and not sensitive to Kantrex, Streptomycin, Gentamicin, Ampicillin, its resistance rate corresponding to100%,85%,80%and65%. Susceptibility testing should be carried out prior to Riemerella anatipestifer disease betreated. Chinese Traditional Medicine is the best choice for curing the disease, not only because ithas good RA-Disease treating effect, but also could reducing the antibiotic usage, decreasing theincidence of drug resistance, and improving the quality of duck meat and eggs.