Septic Arthritis Organisms — SCE Rheumatology MCQ
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Correct answer: E — Staphylococcus aureus
Staphylococcus aureus is the most common pathogen causing native-joint septic arthritis in adults. A large contemporary adult cohort found it in 53% of cases, and UK population data confirm that staphylococcal species predominate. Streptococci are important causes, but Streptococcus pyogenes is not the leading organism overall. Neisseria gonorrhoeae should be considered when the clinical and sexual history suggests disseminated gonococcal infection, but it is not the commonest cause in UK adults. Escherichia coli and Pseudomonas aeruginosa are less frequent Gram-negative causes and become more relevant with particular host factors or healthcare and exposure histories. None of these features is present to displace the usual epidemiological answer.
Reference: Kennedy N et al. Epidemiology, Management, and Outcomes of Large and Small Native Joint Septic Arthritis in Adults. Clinical Rheumatology, 2019. https://pubmed.ncbi.nlm.nih.gov/30941403/