Late prosthetic shoulder joint infection due to Actinomyces neuii in an adult man

A 72-year-old man with a history of right reverse shoulder arthroplasty presented with a 1-month history of erythema, pain and drainage from the right shoulder. Arthrocentesis was performed and synovial fluid gram stain revealed gram-positive rods. Clinical diagnosis of prosthetic shoulder joint infection was made. Orthopaedic surgeons performed irrigation and debridement with resection of the right shoulder prothesis and implantation of an antimicrobial spacer. Operative cultures grew Actinomyces neuii The patient was treated with 6 weeks of ceftriaxone with improvement in both clinical symptoms and laboratory values. Actinomyces species remain a rare cause of late prosthetic joint infection (PJI) due to their slow growing and indolent course. While generalised actinomycosis is often treated with 6-12 months of antibiotics, the treatment course of Actinomyces PJI is not well characterised, with some sources suggesting a minimum of 6 weeks of antimicrobial therapy.