Revisiting the Evidence Base That Informs the Use of Adjunctive Therapy for Enterococcus faecalis Endocarditis: A Systematic Review and Meta-Analysis

Abstract Background Guidelines recommend adjunctive gentamicin for the treatment of Enterococcus faecalis infective endocarditis (EFIE) despite a risk of toxicity. We sought to revisit the evidence for adjunctive therapy in EFIE and to synthesize the comparative safety and effectiveness of aminoglycosides versus ceftriaxone by systematic review and meta-analysis. Methods For historical context, we reviewed seminal case series and in vitro studies on the evolution from penicillin monotherapy to modern-day regimens for EFIE. Next, we searched MEDLINE and Embase from inception to 16 January 2024 for studies of EFIE that compared adjunctive aminoglycosides versus ceftriaxone or adjunctive versus monotherapy. Where possible, clinical outcomes were compared between regimens using random effects meta-analysis. Otherwise, data were narratively summarized. Results The meta-analysis was limited to 10 observational studies at high risk of bias (911 patients). Relative to adjunctive ceftriaxone, gentamicin had similar all-cause mortality (risk difference [RD], –0.8%; 95% confidence interval [CI], −5.0 to 3.5), relapse (RD, −0.1%; 95% CI, −2.4 to 2.3), and treatment failure (RD, 1.1%; 95% CI, −1.6 to 3.7) but higher discontinuation due to toxicity (RD, 26.3%; 95% CI, 19.8 to 32.7). The 3 studies that compared adjunctive therapy to monotherapy included only 30 monotherapy patients, and heterogeneity precluded meta-analysis. Conclusions Adjunctive ceftriaxone appeared to be equally effective and less toxic than gentamicin for the treatment of EFIE. The existing evidence does not clearly establish the superiority of either adjunctive therapy or monotherapy. Pending randomized evidence, if adjunctive therapy is to be used, ceftriaxone appears to be a reasonable option.