Sample size is calculated by using plasma concentration of bacterial genomic DNA as the main variable and assuming a power of 95% and an error of 5%. Considering that plasma bacterial genomic DNA concentration was about 45.13±24.54 ng/ul in end stage renal disease(ESRD) patients according to our previous study and a 20% drop out, the investigators estimate that with 1:1 randomisation,at least 36 patients each group have to be enrolled to detect a 50% decrease of plasma concentration of bacterial genomic DNA .