The ratio of pre-dialysis vancomycin trough serum concentration to minimum inhibitory concentration is associated with treatment outcomes in methicillin-resistant Staphylococcus aureus bacteremia

BACKGROUND: Vancomycin is a standard treatment for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, and its efficacy is closely linked to the recommended serum trough concentration of 15–20 mg/L. However, it is unknown how the pre-dialysis trough serum concentration (C(pre-HD)) correlates with MRSA eradication in renal failure patients undergoing intermittent hemodialysis (HD). OBJECTIVE: To evaluate the relationship between C(pre-HD) and the treatment outcomes in this population. MATERIALS AND METHODS: A retrospective study was conducted to enroll renal failure patients undergoing HD who had received vancomycin treatment for MRSA bacteremia during January 2013 to June 2016. Treatment failure was defined as persistent bacteremia after ≥ 7 days of vancomycin therapy or recurrent MRSA infection within 30 days. Patient characteristics, vancomycin dosing regimen, C(pre-HD), vancomycin minimum inhibitory concentration (MIC), and subsequent culture data were reviewed. The receiver operating characteristic (ROC) curve was used to find the optimal cut-off point of C(pre-HD). RESULTS: 42 patients were enrolled and 64% had treatment failure. Although there were no significant differences in demographics or C(pre-HD) between the two groups, C(pre-HD)/MIC was significantly higher in the success group than that in the failure group (22.80±10.90 vs. 14.94±6.11, p = 0.019). The area under the ROC curve was 0.74, while the sensitivity, specificity, positive predictive value, and negative predictive value were 67%, 78%, 62.5%, and 81%, respectively, at the optimal C(pre-HD)/MIC of ≧ 18.6. CONCLUSIONS: C(pre-HD)/MIC was associated with vancomycin treatment outcome in MRSA bacteremia, and targeting to achieve a C(pre-HD)/MIC of ≧ 18.6 may improve treatment outcomes in renal failure patients who are on intermittent HD.