The most common cause of meningitis in children aged 5 yrs is-
**Core Concept**
The question is testing the student's knowledge of the epidemiology of meningitis in children. Meningitis is an inflammation of the protective membranes covering the brain and spinal cord, known as the meninges. In children, the most common causes of meningitis vary with age, with bacterial, viral, and fungal pathogens involved.
**Why the Correct Answer is Right**
The most common cause of meningitis in children aged 5 years is *Streptococcus pneumoniae*. This bacterium is a leading cause of community-acquired bacterial meningitis in children, particularly in those aged 5 years and under. *S. pneumoniae* is a Gram-positive coccus that colonizes the upper respiratory tract and can invade the bloodstream, leading to meningitis.
**Why Each Wrong Option is Incorrect**
* **Option A:** *Haemophilus influenzae type b* is a leading cause of meningitis in children under 5 years, but vaccination has significantly reduced its incidence.
* **Option B:** *Neisseria meningitidis* is a common cause of meningitis in adolescents and young adults, but its incidence peaks later than the age of 5 years.
* **Option C:** *Cryptococcus neoformans* is a fungal pathogen that causes meningitis, particularly in immunocompromised individuals, but it is not the most common cause in children aged 5 years.
**Clinical Pearl / High-Yield Fact**
The conjugate pneumococcal vaccine has been shown to reduce the incidence of *S. pneumoniae* meningitis in children, highlighting the importance of vaccination in preventing this serious infection.
**Correct Answer:** C. *Streptococcus pneumoniae*