Question

The most common cause of bacterial meningitis in adults is:

• A. Escherichia coli
• B. Streptococcus pneumoniae
• C. Listeria monocytogenes
• D. Haemophilus influenzae

Hint:

In adults: S. pneumoniae and N. meningitidis are top causes; in neonates: GBS and E. coli.

Answer 1

The Correct Option is B

Step 1: Understanding bacterial meningitis
Bacterial meningitis is a severe infection of the protective membranes (meninges) covering the brain and spinal cord. It is a medical emergency due to its rapid progression and high risk of mortality or neurological damage if not treated promptly.

Step 2: Most common cause in adults
In adults, the most common cause of bacterial meningitis is Streptococcus pneumoniae. This gram-positive, encapsulated bacterium can spread from infections in the respiratory tract, sinuses, or ears to the meninges.

Step 3: Key features of Streptococcus pneumoniae meningitis

• Rapid onset of symptoms: fever, headache, neck stiffness, and altered mental status.
• High mortality rate if untreated.
• Often associated with pneumonia or otitis media as the primary infection source.

Step 4: Why other options are incorrect

• Escherichia coli: More common in neonates, not in adults.
• Listeria monocytogenes: Affects neonates, elderly, and immunocompromised adults, but not the most common in healthy adults.
• Haemophilus influenzae: Previously a common cause in children, now rare due to the Hib vaccine.

Step 5: Clinical importance
Early diagnosis and empirical antibiotic therapy targeting S. pneumoniae can greatly reduce complications. Vaccination with the pneumococcal vaccine is an important preventive measure, especially in high-risk populations.

Streptococcus pneumoniae = Leading cause of bacterial meningitis in adults