Review Question - QID 218648

A 19-month-old female is seen in the ER for 2 days of irritability and left hip pain. The patient's parents deny any antecedent trauma and note that the patient is fully vaccinated. She refuses to bear weight on her left leg. The patient's temperature is 38.0°C (100.4°F). On physical examination, the hip is held in resting flexion and external rotation. Any movement of the hip elicits pain. Laboratory studies show a white blood cell count of 10,200/mm3, ESR of 21 mm/hr, and CRP of 14 mg/L. Ultrasound shows a small effusion compared to the contralateral hip, and synovial fluid analysis shows white blood cells of 76,000/mm3 with 90% polymorphonuclear leukocytes. Immediate operative irrigation and debridement is performed. Cultures from both the initial aspiration and intraoperative tissue cultures remain negative at 14 days. Which of the following describes the most likely organism?