Establish Quantitative PCR to Measure Bacteria Load of the VRE Bacteremia

The investigators hypothesized that quantitative PCR can be used in VRE bacteremia outcome monitoring. Vancomycin-resistant enterococci (VRE) was first found in 1988 and has become an important healthcare-associated pathogen due to rapid spread, limited options for therapy and the possibility of transferring vancomycin resistance to more virulent pathogens. VRE infections not only contribute to more hospital cost and longer length of hospital stay, but also higher attributable mortality compared to those caused by vancomycin susceptible enterococci. Two different meta-analyses have shown that vancomycin resistance is an independent predictor of death among patients with enterococcal bloodstrem infections (BSIs). Despite this, few effective antibiotics are approved by the US Food and Drug Administration for the treatment of serious VRE infections. Though several studies have conducted to find the possible mortality predictors, but none has used bacterial load as a marker. Schonheyder et al. have used semiquantitative culture, and demonstrate the relationship between high bacterial load and mortality. However, it may take more than two days before culture result available, and the sensitivity of culture is greatly affected by antimicrobial treatment. Real-time PCR has been demonstrate good performance in early detection of bacteremia, and theoretically is less affected by antimicrobial usage. However, using quantitative real-time PCR to quantify VRE in blood has not been explored, yet. The objective of this study is to establish a quantitative method to measure the amounts of VRE in blood using the VRE specific van gene. And test the hypothesis that higher VRE load in blood results in higher mortality among patients with VRE BSIs. Primers and probe of VRE Real-time PCR will be constructed first. The investigators will prospective enroll patient with VRE bacteremia. Clinical data and outcome will be monitored. Bacteria load of VRE bacteremia will be measured via est