**Core Concept**
The spleen plays a crucial role in the immune system, particularly in filtering the blood and storing lymphocytes. After splenectomy, patients are at an increased risk of infections due to the loss of these immune functions. Capsulated bacteria are a specific type of pathogen that are more virulent in individuals with impaired immune systems.

**Why the Correct Answer is Right**
Capsulated bacteria are more likely to cause infections in patients who have undergone splenectomy due to their ability to evade the host's immune response. The capsule, a thick layer of polysaccharides or glycoproteins, prevents the bacteria from being phagocytosed by neutrophils and macrophages. Without a functioning spleen, patients are more susceptible to infections caused by these encapsulated bacteria, such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis.

**Why Each Wrong Option is Incorrect**
**Option A:** Uncapsulated bacteria are not typically associated with increased risk of infection in splenectomized patients, as they are more easily phagocytosed by host immune cells.
**Option C:** Gram-positive sepsis is a possible complication of splenectomy, but it is not the most common type of infection. Gram-positive bacteria are more commonly associated with skin and soft tissue infections.
**Option D:** Gram-negative bacteria can cause a range of infections, but they are not the most common type of infection in splenectomized patients.

**Clinical Pearl / High-Yield Fact**
Patients who have undergone splenectomy should be vaccinated against encapsulated bacteria, such as Streptococcus pneumoniae and Haemophilus influenzae type b, to reduce their risk of infection.

**✓ Correct Answer: B. Capsulated bacteria**