An 8-year-old boy complains of left leg pain for 3 days. On physical examination, his temperature is 38.9degC, and he exhibits irritability when his left leg is moved. A radiograph of the left leg shows changes suggesting acute osteomyelitis in the proximal portion of the left femur. Culture of the infected bone is most likely to grow which of the following organisms?

Staphylococcus aureus is the most common cause of osteomyelitis in children and adults. Infections with H. influenzae may occur in children less than 2 years of age, but vaccination has reduced the incidence of such cases. Both organisms can cause congenital infections. Gonorrhea as a cause of acute osteomyelitis should be considered in sexually active adults and may be passed to the fetus in the birth canal, but typically involve the eyes. Salmonella osteomyelitis is most characteristic of individuals with sickle cell anemia. Pneumococcal osteomyelitis is uncommon.