Effect Of Inactivated Enterococcus Faecium On Salmonella Infection In Mice

As a feed additive,probiotics are widely used in large-scale livestock and poultry farming,and their feeding effects have been widely recognized by livestock practitioners and scholars.In recent years,the laboratory has inactivated Enterococcus faecium in high temperature and high pressure to prepare injections for intravenous injection in mice,and found that it has good immune enhancement and disease prevention effects.In the previous research work in this laboratory,it was found that intravenous injection of Enterococcus faecium preparations has a certain protective effect on mice infected with Salmonella.Therefore,this subject has further carried out related research in the hope of providing new information for the prevention of Salmonella Ways and means.The main research contents and results are as follows:Firstly,inactivated Enterococcus faecium injection was prepared.The cultured Enterococcus faecium was centrifuged to retain the precipitate,washed with physiological saline and prepared into a suspension,and then sterilized at 121°C for 15 minutes under high temperature and high pressure.The bacteria were counted using a THOMA counting plate to adjust the bacteria.The amount was 1.0×10~9CFU/m L,and this concentration was taken as a1×dose,and based on this,different times of inactivated Enterococcus faecium injections could be prepared.In the experiment,clean-grade Kunming mice were used as the research object.The normal control group,Salmonella model group,1×dose administration group and2×dose administration group were designed,with 10 mice in each group,half male and half female.The dosing schedule was preventive,and Salmonella was inoculated for 24 hours.The effects of intravenous injection of inactivated Enterococcus faecium on Salmonella-infected mice,histopathology,organ bacterial load,blood immune cells,antibodies and cytokines were studied.turn out:(1)Intravenous injection of inactivated Enterococcus faecium can significantly reduce the mortality of mice.After 15 days of observation,all mice in the Salmonella model group died,and 6 mice in the administration group survived.(2)The results of histopathological examination showed that all the hearts of the mice in the Salmonella model group had cardiomyocyte necrosis and inflammatory cell infiltration,while 4 in the 1×administration group,5 in the 2×administration group,and no obvious pathological changes in other mice;all the livers of the mice in the Salmonella model group had hepatocyte necrosis and mononuclear cell infiltration and inflammatory meat infiltration Granuloma,necrotic focus of liver cells,6 lesions in 1×administration group,5 lesions in 2×administration group,no obvious pathological changes in other mice;the spleen of all mice in Salmonella model group showed the increase of red pulp and white pulp space,the increase of red pulp volume,and a variety of immune cells(mainly macrophages,neutrophils,dendritic cells,lymphoid cells)can be seen There were 7 mice in the 1×dose group and 6 mice in the2×dose group,but no obvious pathological changes in other mice.There was no obvious pathological change in lung and kidney.(3)The results showed that the Salmonella load in the heart,liver,spleen,lung and kidney of the mice in the 1×dose group and 2×dose group were significantly lower than that in the Salmonella model group,respectively;the reduction of Salmonella load in the heart in the 2×dose group was significantly stronger than that in the 1×dose group;the reduction of Salmonella load in the liver,spleen,lung and kidney in the 1×dose group was significantly stronger 2×administration group.(4)The number of B cells,CD4~+ cells and Treg cells in the blood,spleen and mesenteric lymph nodes of mice in the 1×administration group and 2×administration group were significantly higher than that in the Salmonella model group(P<0.01).The number of CD4~+cells in the blood of the 1×administration group recovered to the level of the normal control group;the number of B cells,CD4~+cells and Treg cells in the mesenteric lymph nodes of the2×administration group were significantly higher than that in the Salmonella model group(P<0.01)The number of cells was higher than that of the control group.(5)Humoral immunity and cytokine detection showed that the Ig G and IFN-γlevels in the blood of mice in the 1×administration group and 2×administration group were significantly higher than those in the Salmonella model group(P<0.01);the IgA and IL-2concentrations in the serum of mice in the 1×administration group and 2×administration group were not significantly different from those in the normal control group,indicating that they were back to the normal level.In conclusion,intravenous injection of inactivated Enterococcus faecium has a good protective effect on mice infected with Salmonella,which may be related to the regulation of immune function.