Aminoglycosides for Surgically Treated Enterococcal Endocarditis

Aminoglycosides are a mainstay of treatment for enterococcal infective endocarditis. However, the benefit of adding aminoglycosides to cell wall-active agents after surgery is unclear. The aim of this study was to determine if adjunctive aminoglycoside treatment after surgery for enterococcal endocarditis leads to better outcomes. We included patients who underwent surgery for enterococcal endocarditis at our institution between July 2007 and July 2014. Treatment was defined as at least 1 dose of an aminoglycoside after surgery. Propensity to receive aminoglycosides was calculated in a model that included age, native vs prosthetic valve endocarditis, chronic kidney disease, high-level aminoglycoside resistance, metastatic infection, invasive disease, positive valve culture, and creatinine on the day of surgery. A multivariable Cox proportional hazards model was used to compare the primary outcome of death, adjusted for propensity to receive aminoglycosides, among patients who did and did not receive aminoglycosides. A total of 108 patients were identified of whom 37 (34%) received at least 1 dose of an aminoglycoside after surgery, with a median duration of 5 days (interquartile range: 2.5-10). In the multivariable model, patients treated with adjunctive aminoglycoside therapy had better survival than those treated with a cell wall-active agent alone, although the difference did not reach statistical significance (hazard ratio = 0.65, 95% CI: 0.32-1.33). The survival difference was consistently present in subgroups stratified by all-purpose refined diagnosis-related group mortality risk, and with varying definitions of aminoglycoside therapy. In conclusion, antibiotic monotherapy with a cell wall-active agent after surgery for enterococcal endocarditis may be inferior to combination therapy including an aminoglycoside.