Splenectomy and Overwhelming Post-Splenectomy Infection (OPSI)
The spleen is the major site for clearance of blood-borne encapsulated bacteria and for production of opsonizing antibodies (IgM) against polysaccharide capsular antigens. After splenectomy, this filtering and antibody function is lost, placing the patient at lifelong risk of fulminant sepsis known as Overwhelming Post-Splenectomy Infection (OPSI). Asplenic patients are therefore given oral antibiotic prophylaxis (commonly penicillin V or amoxicillin) and vaccinated against the key encapsulated organisms.
Analysis of Options
- Streptococcus pneumoniae (Correct Answer): This is the single most important and most common cause of OPSI, responsible for the majority of post-splenectomy sepsis cases and deaths. Because of this, all splenectomized patients require vaccination (pneumococcal conjugate/polysaccharide vaccines) and long-term oral penicillin prophylaxis specifically targeted against this organism.
- Escherichia coli: A gram-negative bacillus that is not encapsulated in the classic OPSI sense and is not a standard target of post-splenectomy oral prophylaxis; it is more relevant to urinary tract and gram-negative sepsis in other clinical settings.
- Staphylococcus aureus: An important cause of surgical site and skin/soft-tissue infections, but it is not an encapsulated organism cleared primarily by the spleen, and it is not the organism targeted by standard post-splenectomy oral chemoprophylaxis.
- Pneumocystis corinii (jirovecii): This is a fungal-like organism causing pneumonia in states of severe cellular (T-cell) immunodeficiency such as advanced HIV/AIDS or prolonged immunosuppression, not in splenectomy, which primarily impairs humoral clearance of encapsulated bacteria.
Conclusion
The correct answer is Streptococcus pneumoniae, along with Haemophilus influenzae and Neisseria meningitidis (the classic encapsulated triad), being the organisms against which asplenic/splenectomized patients require vaccination and oral antibiotic prophylaxis to prevent OPSI.
Important Questions from Bacterial Infections
Which of the following are major criteria under the Jones Criteria for Acute Rheumatic Fever?
1. Chorea
2. Erythema Marginatum
3. Subcutaneous Nodules
4. Polyarthralgia
Select the correct answer using the code given below:
- Whipple's disease is characterized by the infiltration of small intestinal mucosa by 'foamy' macrophages. Which one of the following histological stains is characteristically used to stain them?
- A young male presented with recent onset urethral discharge and dysuria. On examination, the discharge was profuse and purulent. Microscopy of smears from the discharge revealed Gram-negative diplococci. What is the likely diagnosis?
- Cat-scratch disease is caused by infection of which of the following organisms?
Which of the following drugs is/are useful in the treatment of Listeria monocytogenes infection?
1. Ceftriaxone
2. Gentamicin
3. Ampicillin
4. Sulfamethoxazole
Select the correct answer using the code given below.
