Molecular Epidemiological Surveillance Of HPs, Identification And Biological Characterization Study Of The Disease Agent In Guangxi

Haemophilus parasuis(HPs)is the cause of infectious diseases in pigs, which is characterized by polyserositis,polyarthritis,meningitis,hight mortality, and harmed seriously the developpement of pig industry.In this research,235 samples were collected from 9 cities and 18 regions in Guangxi province,to carry out reseach on the molecular epidemiology,bacterial isolation and identification of the Haemophilus parasuis.The main research results included as follows:1.Molecular epidemiological surveillance of HPsFrom November 2006 to February 2008,235 samples were collected from 9 cities and 18 areas in Guangxi province.According to the sequences of the Haemophilus parasuis 16S rRNA,primer was disigned to carry out PCR amplification.The result was that 14 samples were positive,the positive rate was 5.96%.Positive samples included 4 samples from NanNing,1 sample from WuMing,1 sample from ShangLin,3 samples from LuChuan,1 sample from XingYe,2 samples from XinXing,and 1 sample from TianDeng.It indicated that Haemophilus parasuis already occured in Guangxi province,but it didn't prevaled widespread.2.Cloning and Sequence analysis of the HPs 16S rRNAThe 822 bp amplified fragments was cloned into T-vector and sequenced,sequencing result was blasted into GenBank to carry out sequences comparison.homology analysis were carried using the fourteen positve samples strains and the overseas strains.The results indicated an homology of 94.3%～99.8%,nucleotide homologies of the fourteen strains isolates from Guangxi were 94.5%～100%.It showed that there is not large variation between the Guangxi strains and the overseas strains.(1)From the 14 positive sample tested by PCR assay,7 strains were isolated respectively GXNN3,GXNNST1,GXNNWM1,GXLZXX1,GXLZXX2, GXLZ1,GXYLLC1.After microscopy and biochemistry assay,results indicated batcterial colony characteristic,bacterial morphology and the results of each kind of biochemical reagent reactions were identical with Hps,Hps was confirmed by PCR assay.(2)Drug Susceptibility test was performed by using the 7 positive isolated strains to determine different Drug Sensitivity.Result indicated 7 isolated strains showed different sensitivities to various kinds of drug.Cefradine and Enrofloxacin were most sensitive than Cefazolin and Ofloxacin.Accocrding to this result,clinical treatment was realized in three pig farms of Guangxi,and succeded to control diseases.That proved the experiment result were conformed to the clinical treatment,then offered a precious experience to cure this disease.(3)Virulence detection of the 7 isolated strainsHealthy mouse were intraperitoneally injected(0.5ml)with the purified bacterial suspension,mouse were observed for the detection of the isolated strains virulence.Result indicated that GXLZXX2 and GXLZ1 were strongly more virulent than GXLZWM1,and GXNN3.Others strains showed not virulence case on the mouse body.It showed that there was strong and weak virulence among HPs strains.