A 40-year-old intravenous drug user presents to the emergency depament with a 2 days history of right knee pain with associated swelling and erythema. The patient is febrile with a holosystolic murmur at the right lower sternal border. Complete blood count reveals leukocytosis. Blood and synol fluid cultures are sent, and broad-spectrum antibiotics are staed. Synol fluid analysis is pending. What is the most likely pathogen causing these symptoms: (A) Neisseria gonorrhoeae, (B) Pseudomonas aeruginosa, (C) Borrelia burgdorferi, (D) Staphylococcus aureus
Answer is D. Gram-positive bacteria remain the most common cause of septic ahritis. Staphylococcus aureus accounts for the majority of culture-positive septic ahritis, especially within ceain patient subgroups such as hemodialysis patients and intravenous drug abusers. The predominance of S. aureus in septic ahritis has remained unchanged for many years.