A 75-year-old woman presents the emergency department with a 4-month history of persistent right knee pain and low-grade fever. Three years ago, she underwent total replacement of right knee to treat osteoarthritis. Three months ago, a synovial fluid aspirate was positive for methicillin-sensitive Staphylococcus aureus, with 2500 leukocytes/µL (2.5 x 10 9 /L). She was treated with intravenous, then oral, nafcillin without improvement. Today, the physical examination revealed, 38.0°C (100.4°F) temperature, 135/79 mmHg blood pressure, 86/min pulse rate is 86/min, and 13/min respiration rate is 13/min.
BMI is 19.3. There is a vertical well-healed surgical scar across the anterior surface of the right knee. The knee is slightly warm, with pain on passive range of motion. Current laboratory studies show hemoglobin 11.6 g/dL (116 g/L), leukocyte count 13,500/µL ([13.5 x 10 9 /L], 87%…
