**Question:** True about meningococcal meningitis is:

A. It is caused by a bacteria called Neisseria meningitidis.
B. It is a common disease in children below 5 years of age.
C. Antibiotics are effective in treating meningococcal meningitis.
D. It is always associated with severe sepsis and organ failure.

**Correct Answer:**
A. It is caused by a bacteria called Neisseria meningitidis.

**Core Concept:**
Meningococcal meningitis is a severe bacterial infection of the meninges, the protective membranes that cover the brain and spinal cord. Neisseria meningitidis is a Gram-negative diplococcus bacterium that causes meningococcal meningitis. This bacterium is capable of crossing the blood-brain barrier and causing inflammation in the meninges, leading to symptoms such as fever, headaches, neck stiffness, and altered mental status.

**Why the Correct Answer is Right:**
Meningococcal meningitis is primarily caused by Neisseria meningitidis, which can invade the bloodstream and cause an inflammatory response in the meninges. This bacterial infection is a significant health concern globally due to its high mortality and morbidity rates.

**Why Each Wrong Option is Incorrect:**

B. It is a common disease in children below 5 years of age: While meningococcal meningitis can affect individuals of all ages, it is more common in children under 5 years old. However, the correct answer is not limited to this age group.

C. Antibiotics are effective in treating meningococcal meningitis: While antibiotics can be used to treat meningococcal meningitis, they are not always effective due to antibiotic resistance and the complexity of managing the disease.

D. It is always associated with severe sepsis and organ failure: Meningococcal meningitis can present with severe sepsis and organ failure, but not all cases exhibit these severe manifestations. The correct answer focuses on the primary cause of the disease, which is Neisseria meningitidis.