skip to main content

IVDU Septic Arthritis — SCE Infectious Diseases MCQ

Instant feedback + full explanation. One question, done properly.

ModerateBone & Joint InfectionIVDU Septic ArthritisSCE Infectious Diseases

A 40-year-old man presents with a swollen painful right ankle. He has no recent trauma. He is an IV drug user. Synovial fluid shows 80,000 WCC/µL (95% neutrophils), Gram stain negative, no crystals. He has track marks on his forearms and groin. Blood cultures are pending. In addition to standard septic arthritis management, what specific organism should be considered given his IVDU history?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — MRSA and Pseudomonas aeruginosa — IVDU-associated septic arthritis has a higher prevalence of MRSA and Gram-negative organisms than non-IVDU septic arthritis

IVDU-associated septic arthritis has a broader microbiological spectrum than community-acquired septic arthritis: S. aureus (including MRSA — higher prevalence in IVDU), Pseudomonas aeruginosa, and polymicrobial infections are all more common. Empirical antibiotics should cover MRSA (Vancomycin) and Pseudomonas (Ceftazidime or Meropenem) in addition to standard pathogens. The unusual joint distribution in IVDU (sacroiliac, sternoclavicular, pubic symphysis) should also raise suspicion for IVDU-associated haematogenous seeding. TOE should be performed to exclude endocarditis.

Reference: BSR 2023 – Septic arthritis; NICE NG157 2024