A 70-year-old woman presents with sudden-onset painful, swollen left knee. Arthrocentesis yields 25 mL of synovial fluid with a leukocyte count of 62,000/mm3. Gram stain reveals gram-positive cocci in clusters. Synovial fluid culture grows methicillin-resistant Staphylococcus aureus (MRSA). After appropriate antibiotic therapy and joint drainage, what is the minimum recommended duration of antimicrobial therapy?
- A 7 days
- B 14 days
- C 28 days (4 weeks) ✓
- D 42 days (6 weeks)
Correct answer: C. 28 days (4 weeks)
Explanation
Native joint septic arthritis requires 2 to 4 weeks of parenteral antibiotics, with 4 weeks (28 days) being standard for Staphylococcus aureus, especially MRSA, given its propensity for biofilm formation and destructive joint damage. The IDSA recommends 2 weeks for gram-negative bacilli and 4 weeks for S. aureus. Adjunctive surgical drainage is critical. Transition to oral antibiotics may be considered after clinical improvement with adequate source control.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.