Final answer:
Streptococcus pneumoniae is the most common cause of bacteremia in sickle cell patients due to their increased susceptibility to infections from encapsulated bacteria.
Step-by-step explanation:
The organism that most commonly causes bacteremia in sickle cell patients is Streptococcus pneumoniae. Sickle cell patients are particularly vulnerable to infections from encapsulated bacteria due to splenic dysfunction, which impairs their ability to fight off infections. Streptococcus pneumoniae, a gram-positive bacteria, is associated with pneumococcal pneumonia and has a significant presence as part of the normal microbiota in the human respiratory tract. This pathogen is known to cause severe infections in sickle cell patients, leading to bacteremia and potentially life-threatening complications.