**Core Concept**
Neonatal meningitis is a severe infection of the meninges, the protective membranes surrounding the brain and spinal cord. In newborns, the most common causes of meningitis differ from those in older children and adults. Understanding the typical pathogens responsible for neonatal meningitis is crucial for prompt diagnosis and effective treatment.

**Why the Correct Answer is Right**
E. coli (Escherichia coli) is the most common cause of neonatal meningitis, particularly in the first week of life. This bacterium is commonly found in the gastrointestinal tract and can easily colonize the infant's nasopharynx. Infection occurs when the bacteria breach the blood-brain barrier, often through a breach in the umbilical vein or during delivery. E. coli produces capsular polysaccharides that help evade the host's immune response, allowing it to establish a severe infection. The high incidence of E. coli meningitis in neonates highlights the importance of targeted antibiotic therapy.

**Why Each Wrong Option is Incorrect**
**Option A:** Staphylococcus is a common cause of skin and soft tissue infections but is less frequently associated with neonatal meningitis.
**Option C:** H. influenzae (Haemophilus influenzae) type b is a major cause of meningitis in children but is not typically seen in neonates, as maternal antibodies provide protection in the first few months of life.
**Option D:** Pneumococcus (Streptococcus pneumoniae) is a common cause of meningitis in older children and adults but is less commonly seen in neonates.

**Clinical Pearl / High-Yield Fact**
Neonatal meningitis often presents with non-specific symptoms, such as lethargy, poor feeding, and temperature instability. Prompt recognition of these signs and timely initiation of empirical antibiotic therapy are critical to prevent long-term neurological damage or mortality.

**✓ Correct Answer: B. E. coli**