Q2. A 32-year-old woman with a history of splenectomy presents to the emergency department with sudden-onset high-grade fever, vomiting, hypotension, and rapidly progressive septic shock. Her symptoms began 2 weeks after a minor febrile illness. Which organism is the most likely causative agent of this life-threatening condition?

1. A

   A. Escherichia coli

2. B

   B. Staphylococcus aureus

3. C

   C. Streptococcus pneumoniae

4. D

   D. Pseudomonas aeruginosa

Appeared in: INI-CET EXAM -2026

Explanation

• The patient's history of splenectomy is the most critical piece of information, as it dramatically increases the risk for sepsis from specific pathogens.
• The spleen is essential for clearing encapsulated bacteria from the bloodstream. Without it, these organisms can cause a rapid, fulminant infection known as Overwhelming Post-Splenectomy Infection (OPSI).
• Streptococcus pneumoniae is an encapsulated bacterium and is the most common causative agent of OPSI, accounting for 50-70% of cases.
• The patient's presentation of sudden-onset high fever, hypotension, and septic shock is the classic clinical picture of OPSI.

Why Other Options Were Wrong

• Option A: Escherichia coli is a gram-negative bacillus and a very common cause of sepsis, but it typically originates from the urinary or gastrointestinal tract. It is not the primary pathogen associated with the specific immune defect of asplenia.
• Option B: Staphylococcus aureus is a gram-positive coccus that causes a wide range of infections, including severe sepsis. However, it is not an encapsulated bacterium in the same way as S. pneumoniae, and thus does not pose the same unique, elevated risk to asplenic patients.
• Option D: Pseudomonas aeruginosa is an opportunistic gram-negative bacterium. It typically causes infections in severely immunocompromised patients (e.g., those with neutropenia), patients with cystic fibrosis, or in hospital-acquired settings (e.g., ventilator-associated pneumonia). It is not a common cause of community-acquired sepsis in an asplenic patient.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Etiology of Overwhelming Post-Splenectomy Infection (OPSI) as background academic context rather than a clinical decision trigger.
• A key nursing responsibility for asplenic patients is education about the lifelong risk of infection. Patients must understand the need to seek immediate medical attention for any fever.
• Nurses play a crucial role in ensuring these patients receive and are up-to-date on vaccinations against encapsulated organisms (S. pneumoniae, N. meningitidis, H. influenzae type b).
• Patients should be advised to wear a medical alert bracelet or carry a card indicating their asplenic status, which is vital information in an emergency.

How to Approach the Question

• First, analyze the clinical scenario and identify the most critical piece of patient history. In this case, it is the 'history of splenectomy'.
• Recall the primary immunological function of the spleen, which is to clear encapsulated bacteria from the blood.
• Connect the patient's history (asplenia) with the specific type of infection they are at highest risk for (sepsis from encapsulated organisms).
• Evaluate the given options. Identify which of the listed organisms is the most common encapsulated bacterium responsible for severe, life-threatening infections in asplenic individuals.
• Select Streptococcus pneumoniae as it is the classic and most frequent cause of Overwhelming Post-Splenectomy Infection (OPSI).
• Briefly consider why the other options are less likely. E. coli is usually from a GU/GI source, S. aureus is not the primary encapsulated threat, and Pseudomonas is typically opportunistic or hospital-acquired.

Concept Tested & Keywords

• Concept Tested: Etiology of Overwhelming Post-Splenectomy Infection (OPSI)
• Stem keywords: splenectomy, high-grade fever, hypotension, septic shock, causative agent
• Lead-in keywords: most likely
• Clinical cues: History of splenectomy: This is the critical clue, indicating a compromised immune response to specific types of bacteria (encapsulated organisms).

Question ID

QKZyZ0lkMg4eKBmZt_fZEA

Copy ID

Reference Book

E6 Medicine Harrison 22e Part 1 p. 1031-1033

E6 Medicine Davidson Principles Practice 24e p. 246-248