What encapsulated bacteria pose an infection risk after splenectomy (removal of the spleen)?

Encapsulated Bacteria of Concern After Splenectomy

The three main encapsulated bacteria that pose significant infection risk after splenectomy are Streptococcus pneumoniae (most common, causing 50% of cases), Haemophilus influenzae type B, and Neisseria meningitidis. 1, 2

Overwhelming Post-Splenectomy Infection (OPSI)

OPSI is a life-threatening medical emergency characterized by:

• Fulminant sepsis, meningitis, or pneumonia primarily caused by encapsulated bacteria 1
• Mortality rate of 30-70%, with most deaths occurring within the first 24 hours 1
• Incidence of 0.5-2% in splenectomized patients 1
• Highest risk in the first year after splenectomy, but remains elevated for more than 10 years and likely for life 1, 2

Risk Factors for OPSI

• Children under 5 years have greater overall risk with increased mortality compared to adults 1, 2
• Neonates have a risk exceeding 30% 1
• Hyposplenic patients (those with partially functioning spleens after embolization) should also be considered at risk 1

Specific Pathogens

1. Streptococcus pneumoniae:

   • Accounts for approximately 50% of OPSI cases 1
   • Most common causative organism 2, 3

2. Haemophilus influenzae type B:

   • Second most common cause of OPSI 1, 3

3. Neisseria meningitidis:

   • Third most common cause of OPSI 1, 3
   • Different strains (A, Y, W135) may require additional vaccination for travel to endemic areas 1

4. Other pathogens:

   • Gram-negative bacilli can occasionally cause OPSI 4
   • Capnocytophaga canimorsus from dog bites poses particular risk to asplenic patients 2

Prevention Strategies

Vaccination

• Immunization against encapsulated bacteria is essential 1, 2
• Optimal timing:
  • For elective splenectomy: at least 2 weeks before surgery 1, 2
  • For emergency splenectomy: no sooner than 14 days after surgery 1
  • If discharge occurs before 15 days post-splenectomy, vaccinate before discharge 1
• Annual influenza vaccination is recommended for patients over 6 months of age 1, 2

Antibiotic Prophylaxis

• Antibiotic therapy should be promptly initiated for any sudden onset of unexplained fever, malaise, or chills 1
• Patients should have a home supply of antibiotics for emergency use 1, 2
• Lifelong prophylactic antibiotics may be considered, especially in the first two years after splenectomy 2

Patient Education

• Patients should be educated about their lifelong increased risk of infection 2
• Patients should carry identification indicating their asplenic status 1, 2
• Primary care providers should be informed of the patient's asplenic status 1, 2

Important Caveats

• Current vaccines do not provide complete coverage against all serotypes of encapsulated bacteria 1, 2
• Despite vaccination, breakthrough infections can occur with serotypes not covered by vaccines 5
• Vaccination coverage rates remain suboptimal in many healthcare settings 6
• OPSI can present with non-specific symptoms initially, leading to delayed diagnosis and treatment 5