Antimicrobial Activity Of Selenzing Glycyrrhiza Uralensis Fisch Polysacccharide Combined Antimicrobial Agents And Its Immunomodulatory Effect

Although the medical community has taken various measures to deal with the problem of bacterial resistance,this phenomenon is still increasing,so how to alleviate this phenomenon has become a hot spot of worldwide concern.However,the development of new chemosynthetic drugs with antimicrobial activity is difficult and the cycle is relatively long.Therefore,more and more researchers pay more attention to the precious Chinese herbal medicines which have nearly a thousand years of development history in China.Objective:By further studying the antibacterial activity of Selenzing Glycyrrhiza uralensis Fisch polysacccharide（SeGUP）and the antimicrobial activity and immunomodulatory effect of its combined antibacterial preparations,It provides a new direction for seeking a method that can slow down the resistance of bacteria and the way and means of preparing antimicrobial active substances,and provides a theoretical basis for the development of safe and effective antimicrobial agents for medicinal animals and plants with regional characteristics.Methods:（1）In vitro bacteriostatic test:Firstly,the bacteriostatic zone of SeGUP was measured by filter paper method.Secondly,the Minimal Inhibitory Concentration against Staphylococcus aureus and Escherichia coli of SeGUP combined with Ceftiofur sodium was determined by double dilution method.MIC),and screen out the bacteria that are more sensitive to SeGUP,and determine the influence on the cell membrane,cell wall,protein concentration in culture medium and the growth curve of the bacteria.And the Fractional Inhibitory Concentration Index（FICI）of SEGUP and its combination with antibiotics,so as to evaluate the in vitro antibacterial effect of SEGUP and its combination with antibiotics.（2）In vivo antibacterial experiment:By bacteriostatic test in vitro,and the use of more sensitive bacteria,establishing mice model of microbial infection,the bacteria to determine by this killed all the mice minimum lethal dose(MLD₁₀₀),and on this basis,the SeGUP filling and uniform in all mice infected with bacteria liquid in advance to evaluate the preventive action;The optimal therapeutic dose of SeGUP combined with antibiotics of different drug doses was selected to detect the therapeutic effect of SeGUP combined with antibiotics on infected mice in vivo.The pathological tissues were collected and made into paraffin sections,and the antibacterial effect of SeGUP and other combined antibiotics in vivo was evaluated by HE staining method.（3）Immune function test:Use cyclophosphamide to establish an immunosuppressive model in mice,collect serum samples after giving high,medium,and low doses of SeGUP,and use ELISA method to detect serum Ig A,Ig G,Ig M,AST,ALT,BUN,AKP content and related cytokine IL-1 and IL-2 content in mouse serum to evaluate the immune effect of SeGUP.Results:（1）In vitro bacteriostatic results showed that SeGUP had in vitro antibacterial effect on Staphylococcus aureus and Escherichia coli.The bacteriostatic zone sizes of high,medium and low dose SeGUP against Staphylococcus aureus were 12.9±0.2 mm,11.0±0.2 mm,9.9±0.2 mm,respectively.The size of inhibitory zone against Escherichia coli were 10.9±0.2 cm,10.0±0.2 mm,9.0±0.2 mm, respectively.MIC values were 100 and 200 mg/mL,respectively.Among the antibacterial drugs,ceftiofure sodium,kanamycin sulfate and enrofloxacin all showed good antibacterial effect,and the size of their antibacterial zone against Staphylococcus aureus was:MIC values of 22.9±0.2 mm,25.2±0.2 mm,21.9±0.2mm were 128μg/mL,125μg/mL,125μg/mL,respectively.The inhibitory zone of Escherichia coli was20.0±0.2 mm,24.9±0.1 mm,10.0±0.2 mm,and the MIC values were 128μg/mL,125μg/mL,250μg/mL,respectively.Therefore,Staphylococcus aureus was selected for the late test.Segup had positive effects on the cell membrane,cell wall,protein concentration and 24 h growth curve of S.aureus,and the effect became better with the increase of the dose.After the combination of antibiotics with SeGUP with different MIC,the FICI values were 0.75 and 1,1.5,respectively.The results were as follows:both ceftiofure sodium and kanamycin sulfate showed good additive effect,while enrofloxacin showed no effect.（2）The results of in vivo antibacterial tests show that SeGUP has a certain effect on the lungs of infected mice in both prevention and treatment,but the preventive effect is relatively weak.The high-dose SeGUP group of 250 mg/kg mice is the best Medication dose group:When it is combined with ceftiofur sodium,1.5 mg/kg of ceftiofur sodium is the best therapeutic effect,which can reduce the original dose of ceftiofur sodium（3 mg/kg）,and compare with ceftiofur sodium.Sodium furfurate alone is effective.（3）Immune test results show that different doses of SeGUP can promote the content of Ig G,Ig A,Ig M,IL-1 and IL-2 in the serum of mice;among them,the effect of SeGUP in the high and medium dose groups is higher than that of the blank control.The difference between the mice in the group was significant（P<0.05）,and the difference was extremely significant compared with the immunosuppression group（P<0.01）,and the measurement of relevant biochemical indicators in the blood of mice showed that the content of AST,ALT,BUN,and AKP There was no significant difference between each dose group of SeGUP and the blank control group（P>0.05）.Conclusion:SeGUP has a certain antibacterial effect in both in vivo and in vitro tests.Its therapeutic effect on infected mice is stronger than its preventive effect.The combination of SeGUP and ceftiofur can not only improve the antibacterial ability of ceftiofur sodium but also Reduce the original dosage of ceftiofur sodium;after using SeGUP,there is no significant difference in the liver and kidney indexes of the mice in the blank control group.Therefore,it preliminarily shows that SeGUP has no obvious damage to the liver and kidney functions of healthy mice.It is also safer and provides a certain possibility for subsequent development and application;the antibacterial effect of SeGUP is related to its effect on bacterial cell membrane,cell wall and protein concentration,and it may also increase the content of certain related immune factors in mouse serum.It is related to the enhancement of immunity.