Study On The Inhibitory Effect And Mechanism Of Quercetin On Staphylococcus Aureus Coa

Staphylococcus aureus(S.aureus)is a common pathogen of hospital-acquired and community-acquired infections.S.aureus poses a severe threat to human health.The foundation and use of antibiotics play an important role in the prevention and control of bacterial infection.However,with the over use of antibacterials,drug resistance is more serious,fewer and fewer antibacterials are available in our clinic treatment.Therefore,there is an urgent need to find a new antibacterial strategy to reduce the production of drug resistance.The proposal of anti-virulence strategy is a new way to solve the resistance of bacteria.The anti-virulence strategy reduced bacterial virulence by reducing the expression or function of virulence factors,which will not increase the survival and selective pressure of bacteria,thereby reducing the generation of drug resistance.S.aureus coagulase Coa is an important virulence factor causing S.aureus infection.It can bind to and activate prothrombin,converting fibrinogen to fibrin and promoting clotting of plasma.The fibrin network formed to protect S.aureus against the host immune phagocytosis.Therefore,choose Coa as a target,screening its inhibitors is of great significance to therapy S.aureus infections.In this study,we use the method of tube coagulation to screen the Chinese medicine monomer which can prolong the coagulation time.The inhibitor quercetin was selected as the research object which do not inhibit the growth of S.aureus,but have good inhibitory effect on Coa.Further we studied the inhibitory effect and mechanism of quercetin on Coa,and its therapeutic effect on catheter infection in vivo and in vitro.Through the experiment of drawing S.aureus growth curve showed that quercetin had no significant inhibitory effect on Staphylococcus aureus Newman.Verified by tube coagulation method and agarose plate blood coagulation coagulation method showed that quercetin can prolong the clotting time of Coa and reduce the Coa coagulation.Via Thermal Shift Assay we found that the Tm of Coa was 6 ? higher than that of the untreated group.Then by computer molecular docking and molecular dynamics simulation illustrates the binding mode,and through the mutation and the fluorescence quenching analysis we found that the binding constants and binding sites of mutant proteins Pro-227 and His-228 were significantly lower than those of Coa.Finally,by building a catheter infection model in vitro and in vivo,we found that quercetin significantly reduced the adhesion of S.aureus on the surface of the catheter in vitro,significantly reduced the quantity of bacteria carried in the catheter and kidney,and reduced the renal abscess.In conclusion,quercetin has an inhibitory effect on Coa activity of S.aureus.Quercetin and Coa interact to improve the thermal stability of Coa.Quercetin is combined with a compact conformation in the "central cavity" of the Coa structure,which is the residual Pro-227 and His-228.Quercetin can inhibit S.aureus catheter-related infection by inhibiting the activity of S.aureus Coa,and provides a way of thinking for the design and development of new drug against S.aureus infection.