Ampicillin-Ceftriaxone vs Ampicillin-Gentamicin for Definitive Therapy of Enterococcus faecalis Infective Endocarditis: A Propensity Score-Matched, Retrospective Cohort Analysis

Background: Ampicillin-ceftriaxone (AC) has emerged as an alternative antibiotic regimen for enterococcal infective endocarditis (EIE) with reduced toxicity compared with ampicillin-gentamicin (AG), but evidence regarding its success in reducing EIE-associated death in the United States is limited. Methods: We conducted a retrospective, propensity score-matched cohort analysis of EIE patients treated with AC or AG between 2010 and 2017 at 3 hospitals in Pittsburgh, Pennsylvania. We assessed all-cause 90-day mortality as the primary outcome and in-hospital mortality, length of hospital stay, hospital readmissions, adverse events, and relapse of bacteremia as the secondary outcomes. Results: A total of 190 patients with EIE (100 treated with AC and 90 with AG) were included. Ninety-day mortality was significantly higher with AC than AG (21% vs 8%; P =. 02). After propensity score matching, 56 patients in each group remained for the outcomes analysis. Documented aminoglycoside resistance, presence of annular or aortic abscess, and complete pacemaker removal were the significantly different variables between the 2 matched cohorts. We observed no statistically significant difference in 90-day mortality between the 2 treatment groups (11% vs 7%; P =. 55). Adverse events were more common in patients treated with AG (25 vs 39; P =. 0091), and more patients in the propensity score-matched AG cohort switched antibiotic regimens than in the AC group (10% vs 49%; P <. 0001). Conclusions: Patients treated with AC demonstrate no significant differences in mortality, treatment failure, or bacteremia relapse compared with AG in a propensity score-matched EIE cohort.