From the Guidelines
Patients with sickle cell disease or asplenia are particularly susceptible to Streptococcus pneumoniae infections due to the spleen's crucial role in clearing encapsulated bacteria from the bloodstream, and therefore, require pneumococcal vaccination and may need prophylactic antibiotics to prevent potentially life-threatening infections. The spleen contains specialized macrophages that recognize and remove encapsulated bacteria like Streptococcus pneumoniae, which are surrounded by polysaccharide capsules that resist phagocytosis elsewhere in the body 1. Without a functioning spleen, these patients cannot effectively filter these bacteria from the bloodstream, leading to an increased risk of severe or fatal infections, including fulminant sepsis by pneumococci 1.
Some key points to consider in the management of these patients include:
- The risk of overwhelming post-splenectomy infection (OPSI) is highest in these patients, with mortality rates reaching 50-70% if infection occurs 1.
- Pneumococcal vaccination (both PCV13 and PPSV23) is essential for these patients, and vaccination should be performed 14 days after surgery or 2 weeks before planned splenectomy at the latest 1.
- Patients with anatomic or functional asplenia should first be vaccinated against Streptococcus pneumoniae with PCV13, 6–12 weeks later with PPSV23, and revaccination should be performed every 6 years 1.
- Prophylactic antibiotics (typically penicillin) may be necessary to prevent potentially life-threatening pneumococcal infections in these patients 1.
Overall, the management of patients with sickle cell disease or asplenia requires a comprehensive approach that includes pneumococcal vaccination, prophylactic antibiotics, and prompt medical attention in case of suspected infection, to reduce the risk of morbidity and mortality associated with Streptococcus pneumoniae infections 1.
From the Research
Susceptibility to Streptococcus pneumoniae
Patients with sickle cell disease or asplenic patients are particularly susceptible to Streptococcus pneumoniae due to several factors, including:
- Functional asplenia, which occurs in patients with sickle cell disease from a very early age, leading to impaired immune function 2
- Defects in immune function associated with anemia, tissue infarction, and impaired adaptive immunity 2
- Increased risk of invasive infections from encapsulated bacteria, including Streptococcus pneumoniae, due to autosplenectomy 3
- Impaired antibody response, antibiotic drug resistance, and poor response to immunization 4
Role of Virulence Factors
Streptococcus pneumoniae has developed virulence factors, such as:
- Hydrogen peroxide (H2O2), which is produced by the bacteria as a virulence strategy 4
- Pneumolysin (PLY), a pore-forming exotoxin that is a potent mediator of lung injury in patients with pneumonia, particularly in those with sickle cell disease 4
Impact of Prophylaxis and Vaccination
Prophylactic antibiotics and vaccination against Streptococcus pneumoniae can help reduce the risk of infection, but:
- Current vaccination programs may not provide complete protection, and breakthrough cases of invasive pneumococcal disease can occur 3
- The emergence of gram-negative organisms as the cause of infections in patients with sickle cell disease has been observed, highlighting the need for continued vigilance and adaptation of prophylactic strategies 5
- Historical data have shown that antibiotic prophylaxis can provide a protective effect, but compliance and optimal duration of treatment remain concerns 6