A 15-year-old boy with sickle cell disease is brought to the emergency department due to 2 days of fever and severe pain in the left knee. The patient has been hospitalized previously for acute vasoocclusive crises, which generally occur in his arms. His temperature is 38.2 C (100.8 F). Physical examination shows marked tenderness and swelling over the proximal tibia. Laboratory studies reveal leukocytosis and an elevated C-reactive protein. MRI of the left leg shows marked inflammation of the proximal tibia without joint effusion. Blood culture is obtained. Which of the following is the most appropriate choice of empiric antibiotic therapy?

Question

A 15-year-old boy with sickle cell disease is brought to the emergency department due to 2 days of fever and severe pain in the left knee.  The patient has been hospitalized previously for acute vasoocclusive crises, which generally occur in his arms.  His temperature is 38.2 C (100.8 F).  Physical examination shows marked tenderness and swelling over the proximal tibia.  Laboratory studies reveal leukocytosis and an elevated C-reactive protein.  MRI of the left leg shows marked inflammation of the proximal tibia without joint effusion.  Blood culture is obtained.  Which of the following is the most appropriate choice of empiric antibiotic therapy?

Quizplus · Accepted Answer

11ec25c8_d922_3fa3_bc81_1b2f649d9092_MD0003_00 This patient's fever, leg pain, and MRI findings are concerning for osteomyelitis. Patients with sickle cell disease (SCD) are at increased risk for osteomyelitis because impaired blood flow of sickled cells through narrow metaphyseal vessels causes microinfarctions that act as a nidus for infection. In addition, splenic infarctions render patients with SCD functionally asplenic and therefore more susceptible to infection with encapsulated organisms. Staphylococcus aureus and Salmonella are the most common causes of osteomyelitis in children with SCD. Although S aureus is the predominant pathogen in patients without SCD, Salmonella is an encapsulated gram-negative organism that accounts for a large proportion of osteomyelitis in children with SCD. Therefore, empiric antibiotics in a child with SCD should include not only antistaphylococcal therapy (eg, clindamycin) but also a third-generation cephalosporin (eg, ceftriaxone) for Salmonella coverage. (Choices A, C, and E) Cefazolin and oxacillin cover methicillin-susceptible S aureus; clindamycin and vancomycin provide additional coverage against methicillin-resistant strains. However, none provide coverage against Salmonella and therefore are insufficient empiric therapy for this child with SCD. (Choice D) Gentamicin is an aminoglycoside that provides coverage against Salmonella but does not cover S aureus. Therefore, gentamicin alone is an insufficient empiric therapy for suspected osteomyelitis. Educational objective: Staphylococcus aureus and Salmonella are the most common causes of osteomyelitis in children with sickle cell disease. Therefore, empiric antibiotics should include antistaphylococcal (eg, clindamycin) and gram-negative (eg, ceftriaxone) coverage. References: Characteristics and outcomes of osteomyelitis in children with sickle cell disease: a 10-year single-center experience. (http://www.ncbi.nlm.nih.gov/pubmed/32065511)

A 15-Year-Old Boy with Sickle Cell Disease Is Brought to the Emergency