Rifampin for Surgically Treated Staphylococcal Infective Endocarditis: A Propensity Score-Adjusted Cohort Study

Background Rifampin is recommended as adjunctive treatment for staphylococcal prosthetic valve endocarditis (PVE). It is unclear whether this should hold for surgically treated patients. The purpose of this study was to examine whether adjunctive rifampin treatment in addition to cell wall active antimicrobial agents in patients with surgically treated staphylococcal infective endocarditis (IE) results in better outcomes. Methods Patients operated on for staphylococcal IE from April 1, 2008, to July 1, 2014, were identified from our institution's IE registry. Rifampin treatment was defined as 3 or more days of rifampin postoperatively. Cox proportional hazards regression was used to compare a composite outcome of death or reoperation for IE relapse, between patients treated and not treated with rifampin, adjusted for propensity to be treated with rifampin, methicillin resistance, all-purpose refined diagnosis related group (APR-DRG) severity score, and APR-DRG mortality risk. Results In all, 273 patients were identified. The mean age was 56 years, 66% were male, 50% had PVE, 60% had S. aureus or S. lugdunensis infection, 89% had left side involvement, and 57% had invasive disease. Fifty-one (27%) received 3 or more days of rifampin postoperatively. Ninety-two patients died or underwent reoperation for IE relapse at a median of 205 days (interquartile range 56 to 718 days). In a multivariable model, patients treated with rifampin had a similar hazard of death or reoperation for IE relapse as those not treated (hazard ratio 0.76, 95% confidence interval 0.44 to 1.32, p value 0.34). The results were robust to varying definitions of rifampin treatment. Conclusions Among patients with surgically treated staphylococcal IE there was insufficient evidence to claim a reoperation-free survival benefit from treatment with rifampin. Rifampin should not be used as adjunctive therapy for staphylococcal IE in patients who have undergone surgical procedures for its treatment.