A retrospective study of Enterococcus faecalis infective endocarditis: comparison of clinical characteristics and outcomes associated with treatment

Introduction: A synergistic antibiotic combination of a penicillin and gentamicin (AG) is recommended first line management of Enterococcus faecalis infective endocarditis (EFIE). We compare the treatment outcomes between the conventional AG regimen to those treated with a combination of penicillin and ceftriaxone (AC). Given reported beta lactam toxicity risks, we also examine the difference in treatment outcomes between regimens of low dose, 1g 12 hourly (AC L ) and high dose ceftriaxone, 2g 12 hourly (AC N ) in combination with penicillin. Methods: A retrospective cohort study of patients treated for EFIE at single tertiary centre (2012–2019). Outcome measures examined are 90 & 180-day mortality, treatment associated adverse events, and relapse of bacteremia (within 1 year). Results: 39 patients were enrolled [59% given (AC) ( n  = 24), 24% received AC L ( n  = 10) and 34% received AC N ( n  = 14)]. 39% received AG ( n  = 15). We found no significant difference in the mortality outcomes at 90 and 180 days between: a) those treated with a gentamicin combination and ceftriaxone combination overall (P = .114, P = .061) and b) between high and low dose ceftriaxone (P = 1.0, P = .673). No significant difference was noted between the above groups in incidence of relapsed bacteremia (P = .662, P = .414). A greater number of adverse events was observed in the gentamicin group compared to the overall ceftriaxone group (P = .009), with no difference between the high and low dose ceftriaxone groups (P = .05). Conclusion: Combination treatment with penicillin/ceftriaxone appears to be as effective (using low and high dose ceftriaxone) as penicillin/gentamicin in EFIE, with a lower rate of adverse events.