An 8-year-old boy is brought to the emergency department due to 24 hours of fever and chills. Temperature is 38.3 C (101 F) . On examination, the patient is lethargic with dry mucous membranes. There are no oropharyngeal lesions, and tympanic membranes are normal. The lungs are clear on auscultation, and heart sounds are normal. The abdomen is soft and nontender. There is no skin rash. Laboratory testing shows a leukocyte count of 24,000/mm³ with 15% bands, 80% neutrophils, and 5% lymphocytes. Peripheral blood smear is shown in the exhibit.
Blood cultures are obtained and intravenous fluids and empiric antibiotics are initiated. The patient's blood cultures are most likely to grow which of the following organisms?

Question

An 8-year-old boy is brought to the emergency department due to 24 hours of fever and chills. Temperature is 38.3 C (101 F) . On examination, the patient is lethargic with dry mucous membranes. There are no oropharyngeal lesions, and tympanic membranes are normal. The lungs are clear on auscultation, and heart sounds are normal. The abdomen is soft and nontender. There is no skin rash. Laboratory testing shows a leukocyte count of 24,000/mm³ with 15% bands, 80% neutrophils, and 5% lymphocytes. Peripheral blood smear is shown in the exhibit.

Blood cultures are obtained and intravenous fluids and empiric antibiotics are initiated. The patient's blood cultures are most likely to grow which of the following organisms?

Quizplus · Accepted Answer

Patients with sickle cell anemia have mutations in the beta-globulin gene that cause hemoglobin to reversibly polymerize when deoxygenated, which leads to the formation of sickled-shaped erythrocytes that clog small capillaries and cause end-organ ischemia. The spleen is particularly vulnerable; repeated microinfarction of splenic vascular beds usually results in functional asplenia within the first 18-36 months of life. Because the spleen produces opsonizing antibodies that are important for clearing encapsulated bacteria from the blood, asplenia is associated with significant risk of fulminant bacterial infections. Streptococcus pneumoniae is the leading pathogen, but Neisseria meningitidis and Haemophilus influenzae are also frequently isolated. Therefore, patients with sickle cell anemia who present with signs/symptoms of infection (eg, fever, chills, leukocytosis) require urgent empiric antibiotic therapy that covers these pathogens. Vaccination (pneumococcal and Haemophilus influenzae type b) is recommended to reduce risk of future infection. (Choices A, B, C, E, and F) Patients with sickle cell anemia are at increased risk for overwhelming bacterial infections with a variety of pathogens. However, S pneumoniae infections are particularly common, accounting for 40%-60% of total bacterial infections in this population. Although Pseudomonas aeruginosa is encapsulated, it is not a common pathogen in patients with sickle cell disease (it occurs more often in those with cystic fibrosis, severe chronic obstructive pulmonary disease, and diabetes mellitus). Patients with sickle cell anemia are also particularly prone to salmonella osteomyelitis. Educational objective: Patients with sickle cell disease become functionally asplenic within the first few years of life due to repeated microinfarction of splenic vascular beds. This dramatically increases the risk for fulminant infections with encapsulated bacterial organisms, particularly Streptococcus pneumoniae. Patients with sickle cell disease are also at increased risk for other bacterial infections, most notably salmonella osteomyelitis.

An 8-Year-Old Boy Is Brought to the Emergency Department Due