2025 Southeastern Residency Conference

Title: Monotherapy versus Combination Therapy in the Treatment of Enterococcus faecalis Bloodstream Infections
 
Authors: Amber D. Fraley, Daniel Anderson, Joshua Eudy
 
Objective: To evaluate the safety and efficacy of monotherapy and combination therapy for E. faecalis bloodstream infections.
 
Self Assessment Question: True or False: At this time, there is a need for more outcomes data for both monotherapy and combination therapy for E. faecalis BSI in the absence of IE.
 
Background: Enterococci are gram-positive facultative anaerobic organisms typically found as normal intestinal flora. The two most common species that cause infections in humans are E. faecalis and E. faecium. Historically, combination antibiotic therapy has been the standard of care in treating infective endocarditis (IE) caused by E. faecalis. However,  practice is occasionally extrapolated to E. faecalis bloodstream infections (BSI) without IE. With a lack of outcomes data to support use, combination therapy is a dogmatic practice based on in vitro data from the 1950s involving two antibiotics seldom used for E. faecalis infections, penicillin and streptomycin. 
Therefore, this study seeks to assess the safety and efficacy of monotherapy compared to combination therapy for E. faecalis BSI with or without IE.
 
Methods: This single-center, IRB-approved, propensity-matched, retrospective cohort study, conducted at Wellstar MCG Health, reviewed all adult patients hospitalized between January 1, 2017 and September 30, 2024 with at least one blood culture positive for E. faecalis. Patients were excluded from the study if they expired within 72 hours of index culture, had polymicrobial BSI, did not receive antibiotic treatment, and/or had a prior diagnosis of E. faecalis within the previous 60 days. The primary outcome was a composite of 30-day mortality, 60-day hospital readmission, and/or 60-day recurrence. Secondary outcomes were each individual component of the composite outcome, time to blood culture clearance, duration of bacteremia, length of hospital stay, and adverse events. Outcomes were evaluated using various statistical methods, including chi-squared and Mann-Whitney U, as appropriate. Demographics were evaluated using descriptive statistics. 
 
Results: Of the 139 patients who met the inclusion criteria, there was no statistically significant difference in the primary composite outcome for monotherapy compared to combination therapy (27.1% vs 27.8%; p=0.93), hospital length of stay (12.8 [8.1-24.8] vs​ 15 [8.6-23]; p=0.92), or​ adverse reactions (2.5% vs 5.6%; p=0.96).
 
Conclusion: Both monotherapy and combination therapy yielded similar outcomes for the primary composite and adverse reactions​, however, the study was not adequately powered to detect a difference. Therefore, at this time, larger studies are warranted comparing monotherapy and combination therapy for E. faecalis BSI with or without IE.
 
Contact Information: amber.fraley@wellstar.org