Clinical Characteristics and Management of Prosthetic Joint Infections Due Exclusively to Enterococcus Spp: A Ten-Year Retrospective Study

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Background Prosthetic joint infections (PJIs) occur in up to 2% of surgeries and represent a rare but serious complication associated with impaired function, decreased quality of life, and substantial economic burden. Enterococcus spp. account for approximately 4% of PJIs and have been associated with an increased failure risk. However, available data remain limited and largely derived from polymicrobial infections. We aimed to describe monomicrobial Enterococcus spp. PJIs and to identify factors associated with failure. Methods We conducted a retrospective multicentre study across seven university hospitals in France. Adult patients diagnosed with hip or knee PJIs caused exclusively by Enterococcus spp. bewteen January 1, 2014 and December 31, 2023 were included. Clinical characteristics and therapeutic management were analysed to identify factors associated with one-year failure. A secondary objective was to compare outcomes between early oral switch (≤7days) and late or intravenous-only therapy. To adress immortal time bias, oral switch was modelled as a time-dependent covariate in a Cox proportional hazards model adjusted for a Disease Risk Score (DRS) integrating age, sex, Charlson score, BMI, prosthesis location, infection type, blood cultures, and prior surgeries. A landmark analysis at day 7 was performed as a sensitivity analysis. Results Fifty-six patients were included; median age was 76years [IQR:68-82] and 34 (61%) were male. Most frequent comorbidites were diabetes (28%), chronic renal failure (21%). E. faecalis accounted for 92% of isolates. Surgical management included one-stage exchange (50%), two-stage exchange (29%), and DAIR (21%). Among the 12 patients who underwent DAIR, 7 were performed outside the recommended timeframe and appeared to be associated with worse outcomes. Overall one-year success rate was 77%. Oral antibiotic therapy was initiated in 88% of patients, with amoxicillin used in 76% of cases, most commonly at 6g/day. Combination therapy was used in 36% of cases. Twenty-two patients (39%) had an early oral realy. Groups differed in Charlson score (1 [IQR:0-2] vs 2 [1-2.8], p-value:0.046) and median hospital stay (15 days [IQR:13-26] vs 24 days [IQR 16-34], p-value=0.04). Early oral switch was not associated with increased treatment failure in time dependant Cox analysis (HR 1.11 [95%CI:0.19-6.42], with consistent landmark analysis at day 7. Conclusion In this cohort of monomicrobial Enterococcus spp PJIs, outcomes were comparable to those generally reported for PJIs. Early oral switch was not associated with an increased risk of treatment failure and may represent a feasible strategy with potential benefits in terms of hospital stay and patient management.