**Core Concept**
The question is testing knowledge of the microbial etiology of meningitis, specifically the organisms that commonly cause this condition, particularly in relation to ear discharge. The correct answer involves a bacterium that is known to cause meningitis and is often associated with otitis media (inflammation of the middle ear).

**Why the Correct Answer is Right**
The correct answer is **Haemophilus influenzae** type b (Hib). This bacterium is a leading cause of bacterial meningitis, particularly in children, and is often found in the ear discharge of individuals with otitis media. Hib produces a polysaccharide capsule that protects it from phagocytosis, allowing it to cause invasive disease, including meningitis. The bacterium is transmitted through respiratory droplets and can colonize the nasopharynx before invading the bloodstream and central nervous system.

**Why Each Wrong Option is Incorrect**
* **Option A:** Streptococcus pneumoniae is a common cause of otitis media and meningitis, but it is not as strongly associated with ear discharge as Haemophilus influenzae.
* **Option B:** Neisseria meningitidis is a leading cause of bacterial meningitis, but it is more commonly associated with septic arthritis and meningococcemia rather than otitis media.
* **Option D:** Staphylococcus aureus is a common cause of skin and soft tissue infections, but it is not typically associated with meningitis or otitis media.

**Clinical Pearl / High-Yield Fact**
Hib meningitis is a medical emergency that requires prompt recognition and treatment. The Hib conjugate vaccine has significantly reduced the incidence of Hib meningitis in vaccinated populations.

**Correct Answer:** C. Haemophilus influenzae type b