Case 4

1. Presented by Robert Kruse, MD, PhD and reviewed by Patricia Simner, MSc, PhD

Clinical vignette
A young adult with a history of hemoglobin SS disease with complications including sickle cell nephropathy and iron overload. The patient has a history of acute chest syndrome, treated with simple transfusions and then transitioned to red cell exchanges to decrease iron overload. Since starting red cell exchange (RCE) procedures, the patient reports no sickle crises in the last two years. The patient presented with fever (102.3F), chills, generalized body aches, fatigue, and non-productive cough. The patient had a RCE procedure one week prior, and no recent travel history, sick contacts, or other unusual exposures. A rapid flu test was negative in the emergency department and the patient reported the current symptoms were not similar to their pain crisis symptoms. The patient was admitted and blood cultures (2x) were negative. A respiratory viral panel of nucleic acid testing for Influenza A&B, RSV, Parainfuenza 1-4, Rhinovirus/Enterovirus, Metapneumovirus, and Adenovirus was negative. Furthermore, the patient showed no improvement on empiric ceftriaxone and azithromycin for community acquired pneumonia. Searching for other etiologies for a fever of unknown origin, a thick and thin blood smear for blood parasites was ordered. Microscopic image of the thin smear is shown below:

Question: Which of the following is the most likely causative organism?