Most common infection causing OPSI after splenectomy
**Core Concept**
OPSI (Overwhelming Post-Splenectomy Infection) is a life-threatening complication that occurs in individuals who have undergone splenectomy, particularly those with asplenic or hyposplenic conditions. It is characterized by an increased susceptibility to infections, primarily caused by encapsulated bacteria. The spleen plays a crucial role in filtering the blood and storing lymphocytes, which helps to combat infections.
**Why the Correct Answer is Right**
The most common infections causing OPSI are those caused by encapsulated bacteria, such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis. These bacteria have a polysaccharide capsule that helps them evade the host's immune system. In the absence of a spleen, the body is unable to filter out these bacteria, leading to severe infections. The immune system's inability to recognize and respond to these encapsulated bacteria is the primary mechanism underlying OPSI.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because while other bacteria can cause infections in asplenic individuals, they are not the most common cause of OPSI.
* **Option B:** This option is incorrect because while it is true that some bacteria can cause infections in asplenic individuals, it is not the most common cause of OPSI.
* **Option D:** This option is incorrect because while it is a possible cause of infection in asplenic individuals, it is not the most common cause of OPSI.
**Clinical Pearl / High-Yield Fact**
Asplenic individuals are at increased risk of infections caused by encapsulated bacteria, and vaccination against these bacteria is a crucial preventive measure. The pneumococcal conjugate vaccine (PCV) and the meningococcal conjugate vaccine (MenACWY) are recommended for individuals who have undergone splenectomy.
**Correct Answer:** C.