Traditional Chinese Medicine Monomer On The Virulence Factors Of Actinobacillus Suis

Objective:This study aim at investigating growth and virulence genes expression of A.suis in the mimicking stress environment.Meanwhile,virulence genes expression of A.suis under sub-inhibitory concentration of 15 kinds of traditional Chinese medicine monomer were observed for screening of better virulence genes inhibitor.Method:Growth characteristics of A.suis ATCC15557 strain in many plate medium and fluid nutrient medium were observed for screening best plate medium and fluid nutrient for A.suis.According the stress environment that A.suis could be faced with in the process of infection,four conditions including high temperature(40?,41?,42?),oxidative stress(200?mol/L,300pmol/L,500?mol/L,1mmol/L H2O2),low iron ion stress(200?mol/L,300?mol/L,500?mol/L,lmmol/L DTPA)and acidity stress(pH 5.8,6.2,6.6,7.0)were designed.A.suis was put into these conditions in vitro for 10,20,30,40,50,60 min and the growth rate was observed.Real-time PCR was employed to study the virulence genes expression of A.suis under high temperature(42?),oxidative(1mmol/L H2O2),low iron ion stress(1mmol/L),acidity stress(pH5.8)condition for 20 mins,40 mins and 60 mins.The expression of virulence genes ompA,tbpA,ashC,ApxIII was detected after using of sub-inhibitory concentration of 15 kinds of traditional Chinese medicine monomer on A.suis.Result:1.The best plate medium for A.suis was Sheep Blood Agar Base and the best fluid nutrient was BHI medium.2.The growth rate of A.suis was inhibited under all the four stress conditions,including high temperature(40?,41?,42?),oxidative stress(200?mmol/L,300?mmol/L,500?mmol/L,1mmol/L H2O2),low iron stress(200?mmol/L,300?mmol/L,500?mmol/L,1mmol/L DTPA),acidity stress(pH 5.8,6.2,6.6,7.0).3.After the treatment of four stress conditions for 20mins,40mins and 60mins,most of the virulence gene expression down-regulated under high temperature stress.Under low iron stress,the virulence gene relation with iron(exbD,hgbA,hugZ,tbpA,tbpB)expression up-regulated.Under oxidative stress,virulence gene Apx?,ashA,hugZ and some relation with iron expression up-regulated.Under the acid stress,most of the virulence gene expression up-regulated with more released of exotoxin.4.All the 15 kinds of traditional Chinese medicine monomer can inhibite the growth rate of A.suis with the MIC value between16-64?g/mL5.Compare with the control group,in 8?g/mL sophocarpine groups,the expression of Apx? gene decreased 250 times(P<0.01).In 4?g/mL polydatin groups,the expression of ashC gene decreased 18 times(P<0.01).In 16?g/mL astragaloside groups,the expression of ompA gene decreased 3.6 times(P<0.05).In 16?g/mL polydatin groups,the expression of hgbA gene decreased 25 times(P<0.01).Conclusion:1.After the treatment of four stress conditions for 20 mins,40 mins and 60 mins,most of the virulence gene expression down-regulated at high temperature stress,most of the virulence gene expression up-regulated under low iron ion,oxidative and acid stress2.Sophocarpine can down-regulated the expression of Apx? gene,polydatin can down-regulated the expression of ashC gene and hgbA gene,astragaloside can down-regulated the expression of ompA gene,they can be choosed as candidacy virulence genes inhibitors for further studies.