True statement regarding Pneumococcus is
**Core Concept**
Pneumococcus, also known as Streptococcus pneumoniae, is a Gram-positive bacterium that is a major cause of pneumonia, meningitis, and septicemia. The bacterium's virulence is attributed to its polysaccharide capsule, which is essential for evading the host's immune system.
**Why the Correct Answer is Right**
The correct answer is related to the bacterium's polysaccharide capsule. The capsule is composed of a specific polysaccharide, and the bacterium's ability to produce this capsule is a key factor in its virulence. The capsule prevents phagocytosis by neutrophils and macrophages, allowing the bacterium to establish infection.
**Why Each Wrong Option is Incorrect**
* **Option A:** This statement is incorrect because pneumococcal vaccines target the bacterium's surface proteins, not its polysaccharide capsule.
* **Option B:** This statement is incorrect because pneumococcal infections are not typically caused by a lack of vitamin C; rather, they are caused by bacterial invasion.
* **Option C:** This statement is incorrect because pneumococcal infections are not typically caused by a compromised immune system; rather, they are caused by the bacterium's ability to evade the host's immune system.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that pneumococcal infections are a significant cause of morbidity and mortality, particularly in children and older adults. The pneumococcal conjugate vaccine is recommended for these high-risk populations to prevent invasive pneumococcal disease.
**Correct Answer:** D.