USMLE Question #529: Real Exam Question with Answer & Explanation

A 3-year-old boy with chronic granulomatous disease is brought to the physician because of a 3- week history of fever and warm, red lumps under both arms. His temperature is 38°C (100.4°F). Physical examination shows enlarged, 3-cm, erythematous axillary lymph nodes bilaterally. On palpation, the nodes are tender, fluctuant, and movable. Examination of a fine-needle aspirate from one of the nodes shows gram-positive cocci in clusters. Cultures of the aspirate grow yellow, βhemolytic colonies that are catalase and coagulase positive. A polymerase chain reaction test shows mecA-positive organisms. Which of the following is the most appropriate pharmacotherapy for this patient?