**Core Concept:** Lanceolate shaped Gram positive diplococci are characteristic of Neisseria meningitidis, a bacterium that can cause meningitis in children.

**Why the Correct Answer is Right:** Neisseria meningitidis is a gram-positive bacterium that can cause meningitis, particularly in pediatric patients. In this case, the presence of lanceolate shaped Gram positive diplococci in the cerebrospinal fluid (CSF) examination strongly suggests the presence of these bacteria, leading to the diagnosis of meningitis caused by Neisseria meningitidis.

**Why Each Wrong Option is Incorrect:**

A. Lanceolate shaped Gram positive diplococci can also be found in Streptococcus pneumoniae, which is another common cause of bacterial meningitis in children. However, the question specifically mentions that the Gram staining showed lanceolate shaped bacteria, which is more suggestive of Neisseria meningitidis.

B. While Haemophilus influenzae is also a common cause of bacterial meningitis in children, it typically presents with non-lanceolate shaped Gram-negative diplococci in the CSF. The shape described in the question is more consistent with Neisseria meningitidis.

C. Group A Streptococcus (GAS) is another cause of bacterial meningitis, typically presenting with beta-hemolytic colonies on culture and different Gram staining characteristics. The provided description does not align with the characteristics of Group A Streptococcus.

D. Staphylococcus aureus can cause meningitis, but the shape described does not match the characteristics of S. aureus.

**Clinical Pearl (High-Yield Fact):** Neisseria meningitidis is a significant pathogen, particularly in endemic areas, and can present with a high-grade fever, vomiting, and seizures. Early recognition and initiation of appropriate treatment can significantly improve patient outcomes.