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Prosthetic Joint Infection — SCE Infectious Diseases MCQ

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ModerateBone & Joint InfectionProsthetic Joint InfectionSCE Infectious Diseases

A 65-year-old man presents with chronic hip pain 14 months after total hip replacement. CRP is mildly elevated at 22 mg/L. Plain X-ray shows periprosthetic lucency. Joint aspiration grows Cutibacterium acnes (formerly Propionibacterium acnes) after prolonged culture (14 days). What is the significance of this isolate?

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Correct answer: B — C. acnes is a recognised cause of late prosthetic joint infection, particularly in shoulder and hip replacements; it should be treated

Cutibacterium acnes is an indolent organism that is a genuine pathogen in prosthetic joint infections, especially shoulder and hip replacements. It requires prolonged culture (often >7 days) for isolation, which is why standard 5-day cultures may miss it. Growth from deep tissue samples or synovial fluid (not superficial swabs) in the appropriate clinical context should be considered genuine. Treatment typically involves DAIR if early, or two-stage revision if late, with prolonged antibiotics (Penicillin or Amoxicillin as first-line).

Reference: BSAC 2023 – Prosthetic joint infection; NICE NG157 2024