What is the most common bacterial meningitis pathogen in adults?

• A. Neisseria meningitidis
• B. Listeria monocytogenes
• C. Streptococcus pneumoniae
• D. Haemophilus influenzae

Answer: (C)

Streptococcus pneumoniae is the most frequent cause of bacterial meningitis in adults. It commonly colonizes the nasopharynx and has a high propensity to invade the meninges, making it the leading cause of community-acquired meningitis in adults. Neisseria meningitidis is a major culprit in younger individuals, while Listeria monocytogenes poses greater risk for older adults and immunocompromised patients, and Haemophilus influenzae has declined in many areas due to vaccination. When treating an adult with suspected meningitis, coverage for pneumococcus is essential because it accounts for the majority of cases.