Etiological Investigation Of Bovine Endometritis And Pathogenicity Test Of Trueperella Pyogenes

In the last several decades,along with the rapid development of dairy industry and scale livestock,however endometritis caused serious economic losses to the dairy industry in China.There was no relevant literature report on the etiologies of endometritis of the large-scale dairy farms in Shaanxi Province over the past decade.The isolation rates of Trueperella pyogenes was high in Shaanxi Province that was found by our laboratory.This study investigated the etiology of endometritis in a large-scale farm in Weinan,Shaanxi Province,identified Trueperella pyogenes in the endometritis disease samples,and carried out pathogenic analysis.The results showed:1.The etiological investigation of endometritis was performed in a large-scale dairy farm in Weinan,Shaanxi Province.The results showed that the incidence rates in July and August was 44.4%and 41.1%,higher than those other months,the relationship between incidence rates and parity showed a U-shaped association,and the incidence rates of cows in primiparous,and above 5-6 parity was high that more than 29.0%;the incidence rates of endometritis in dairy cows with twins was 56.4%,which was higher than the dairy cows with singletons(24.6%).The incidence rates of endometritis after abortion,dystocia,and retained placenta in dairy cows was more than 45.0%,which was higher than the dairy cows after natural delivery(24.7%).2.Seven strains of bacteria were isolated from 30 uterine mucus samples of dairy cows with endometritis from Shaanxi Province.The bacteria formed small,gray-white,smooth,moist,and hemolytic colonies on the BHI agar medium with 10%sheep blood,which were Gram-positive and rod-shaped bacteria,and these bacteria had more than 99%homology with the 16S r RNA gene sequence of Trueperella pyogenes registered in Gen Bank.The seven strains isolated were confirmed as Trueperella pyogenes.PCR was used for the evaluation of the presence of Trueperella pyogenes virulence factor genes.The results showed that all strains carried plo,fim A and fim C genes.The detection rates of fim E,nan H and nan P were 85.7%,57.1%and 57.1%respectively,cbp A and fim G genes were not detected.3.Mice were injected with 1.5×10~8CFU/mL Trueperella pyogenes from bovine into abdominal cavities(0.5 m L).Two days post inoculated,experimental mice appeared clinical symptoms such as loss of appetite and depression.Five days post inoculated,all experimental mice died.The abdominal cavities of the dead mice were filled with pus,some organs showed purulent foci,and Trueperella pyogenes could be isolated from the diseased tissues,indicating that Trueperella pyogenes from bovine was pathogenic.Mice were administered with 1.5×10~8CFU/mL Trueperella pyogenes from bovine intravaginally(30μL).Experimental mice were found that uterine congestion and edema,and the uterine index was significantly higher than control mice on the 3rd to 7th days after inoculation(P<0.05).Microscopic examination showed that the uterine tissue structure was blurred,lots of inflammatory cells and exfoliated endometrial epithelial cells were observed in the uterine lumen,and the concentration of inflammatory factors IL-1β,IL-6,and TNF-αin the uterine tissue were significantly higher than control mice(P<0.05).The results showed that Trueperella pyogenes from bovine could damage endometrial cells,increase the expression of inflammatory factors in uterine tissue,caused endometritis.