Studies on Etiological Characteristics of Haemophilus Parasuis Isolated from Jiangxi Province
|School||Jiangxi Agricultural University,|
|Course||Preventive Veterinary Medicine|
|Keywords||Haemophilus parasuis isolation and identification serotype fingerprints LD50 drug sensitivity|
Content:Haemophilus parasuis is the etiology of Glasser’s Disease, which cause the porcine polyserositis,arthritis and meningitis,and also has became one of the main reasons of morbidity and mortality of nursery,and caused heavy economic losses.Therefore,it is indispensable and imperative to carry out the research on isolation, serotype and drug sensitive tests on Haemophilus parasuis of Jiangxi Province,which could also provided the basis to futher researches and the disease caused by it.In this study,28 strains of bacterium,which were identificated as Haemophilus parasuis by cultivation, biochemisty and PCR assay,were isolated from 94 samples characterized by serofibrinous fibrinopurulent polyserositis,arthritis and meningitis,from 35 large-scale farms in Jiangxi province. The results of Biological characteristics showed thant different bacterial morphology were observed from different organs.Ususlly,the bacterial newly isolated from synovial fluid or pericardial fluid were rod,while filiform when separated from lungs,then became rod bacillus after several time’s transfer on culture meadia.In this expriment,Haemophilus parasuis was not the only pathogen in those positive samples,but also along with other etiologies, the highest co-infection was PRRSV,then was PCV-2 and the lowest was CSFV.20 strains of Haemophilus parasuis isolated from Jiangxi Province were serotyped by indirect hemagglutination assay.The results showed that serovar 13 was the most prevalent serotype in Jiangxi isolates,with a proportion of 25%,then the serovar 5 and serovar 4 with the prevalence of 15% and 10% respectively,and three of those isolates were nontypable.In order to understand the information of genes of those isolates,a ERIC-PCR assay was used to analysis the fingerprints of them.The results showed that there were 12 different types of fingerprints during those 20 strains,which indicated genetic discrepancy of Haemophilus parasuis Jiangxi isolates and also genetic diversity of the Jiangxi prevenlence strains.To study the virulence of Haemophilus parasuis Jiangxi isolates and its distribution in the organs of mice.Three strains,which were belonged to serovar 5,serovar 4 and serovar 3 respectively, were selected as the experiment bacterium.The lethal dose(LD50) of the 3 strains to Kunming mice were 1.16×109 CFU,1.40×109 CFU and 3.49×109 CFU,the results of which indicated the difference of virulence among different serovars.Lesions and pathological changes were observed in different organs in some of the mice.Lung,liver, spleen and brain of the dead mice were collected to bacterial isolation,the results revealed that Haemophilus parasuis were isolated in all those organs,but the highest separational rate was from lung,while lowest from spleen.A total of 20 Haemophilus parasuis isolates from Jiangxi Province were tested for their susceptibility to 57 antibiotics with a K-B method. The results showed that all the Jiangxi isolates were susceptible to azlocillin,enrofloxacin and vancomycin,but all the bacillus were resistant to the remaining antimicrobials.There were 6 strains resistant to 5 antibiotics of the 57 as used,5 strains to 13 antibiotics and even 2 strains resistant to 22 of those antibiotics. In this study,a PCR assay was established to detect the tetracycline drug resistance gene tet(B),and nine of the 15 isolates resistant to tetracycline was tet(B) positive,which indicated gene tet(B) was one of the main reason that mediate the resistence to tetracycline.