Detection Of Staphylococcus Epidermidis Activity By Electrochemical Method And Screening Of Antibacterial Drugs

Objective This project focused on the electrochemical behavior of S.epidermidis.Specifically,relevant study detected the activity of S.epidermidis by an electrochemical method with xanthine oxidation peak as the indicator,so as to evaluate and screen relevant antibacterial agents,and lay both theoretical and experimental foundations for establishing a rapid,sensitive,simple,and non-toxic low cost electrochemical detection method of S.epidermidis.Methods The electrochemical behavior of S.epidermidis was analyzed by cyclic voltammetry,and for the electrochemical detection,a three-electrode system was adopted:With multi-walled carbon nanotubes modified Glassy Carbon Electrode（MWCNTs/GCE）as the working electrode,saturated argentum/argentum chloride electrode（Ag/AgCl）as the reference electrode,and platinum wire electrode（Pt）as the counter electrode.The electrochemical method,high performance liquid chromatography,plate count method,and turbidimetry were used for a comparative study on the effects of oxidation peak source of S.epidermidis supernatant and incubation time on the activity of S.epidermidis,and the effects of S.epidermidis growth process and drug concentration on the inhibition of antibacterial agents.Results There were two signal peaks detected in the S.epidermidis supernatant by electrochemical method:xanthine oxidation peak（+0.727V）and adenine-hypoxanthine mixed oxidation peak（+1.033V）.Within 1.9～5.6×10⁷ CFU·mL^-1 of bacterial concentration,the current of xanthine oxidation peak was linear with the concentration of S.epidermidis,with linear equation as follows:Y=0.16X+0.28（R²=0.9940）.When the incubation time was more than 6 h,the activity of S.epidermidis decreased.In the electrochemical method,the growth curve plotted with xanthine oxidation peak as indicator was consistent with the trend obtained by plate count method,and thus,the characteristics of changes for growth stages were demonstrated.The effect of drug concentration on antibacterial activity detected by electrochemical method was consistent with the results obtained by the plate count method.The inhibitory effects of gentamicin sulfate,oxacillin sodium,clindamycin hydrochloride and nitrofurantoin on S.epidermidis were compared,and the results showed that gentamicin sulfate had the most significant inhibitory effect on S.epidermidis.Conclusions With xanthine oxidation peak as indicator,the detection results of electrochemical method are consistent with those of plate count method,and furthermore,the electrochemical method is more sensitive than other methods.Overall,the electrochemical method is a rapid,simple,sensitive,non-toxic and accurate method for detecting the activity of S.epidermidis.