Gonococcal Arthritis — RACP Adult Medicine MCQ

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EasyInfectious DiseasesGonococcal ArthritisRACP Adult Medicine

A 35-year-old woman presents with acute monoarthritis of the right knee. She is febrile (39°C). Joint aspiration yields 40 mL of purulent fluid. Gram stain shows Gram-negative intracellular diplococci. She has a recent history of unprotected sexual contact. What is the most likely organism?

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Correct answer: C — Kingella kingae

Gram-negative intracellular diplococci in synovial fluid from a sexually active young adult is pathognomonic for gonococcal arthritis (Neisseria gonorrhoeae). Gonococcal arthritis is the most common cause of septic arthritis in sexually active young adults. It may present as monoarthritis or as a disseminated gonococcal infection (DGI) with the triad of migratory polyarthralgia, tenosynovitis, and dermatitis (pustular skin lesions). Treatment is IV ceftriaxone 1 g daily. Sexual health screening (chlamydia, HIV, syphilis) and partner notification are essential.

Reference: eTG – 2025 – Antibiotic Guidelines; CDNA – 2024 – Gonococcal Infection Guidelines