Methicillin-resistant Staphylococcus epidermidis knee prosthetic infection treatment with two-stage revision and fosfomycin–rifampin combination therapy: a case report

Background: Staphylococcus epidermidis is one of the pathogens most commonly involved in prosthetic joint infections, and when methicillin resistant, poses significant challenges in treatment, owing to its virulence and antibiotic resistance. Intravenous fosfomycin disodium is a broad-spectrum antibiotic recently introduced in clinical practice for treating osteoarticular infections caused by Gram-negative and Gram-positive bacteria, including multidrug-resistant pathogens. Continuous infusion administration of fosfomycin, by an elastomeric pump, is feasible thanks to its good stability at room temperature after reconstitution in aqueous solution. This report describes the case of a methicillin-resistant Staphylococcus epidermidis knee prosthetic infection successfully treated with a two-stage revision coupled with a combination therapy of oral rifampin plus continuous infusion of fosfomycin administrated by an elastomeric pump, filled daily through an outpatient parenteral antimicrobial treatment service. Case presentation: A 31-year-old Italian woman presented right knee pain and functional limitation. A previous diagnosis of pigmentous villonodular synovitis led to destructive arthropathy requiring total knee arthroplasty and extensive synovectomy. Three months later, a methicillin-resistant Staphylococcus epidermidis prosthetic infection was diagnosed and a two-stage procedure was adopted with spacer cement positioning for 4 months, followed by removal and definitive total knee arthroplasty. The methicillin-resistant Staphylococcus epidermidis infection was successfully treated with a combination therapy of oral rifampin plus continuous infusion fosfomycin by an elastomeric pump. At 1-year postoperative follow-up, no complication was detected and the patient was satisfied. Conclusion: This case underscores the effectiveness of combining a two-stage revision procedure with continuous infusion fosfomycin and rifampin for managing complex methicillin-resistant Staphylococcus epidermidis prosthetic infection.