An 18-year-old college student presents with headache, lethargy, fever, neck stiffness, and seizures. What organism is the probable cause?

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

Answer: (B)

Meningitis in a healthy young adult, especially one living in close quarters like a college dorm, is most likely due to Neisseria meningitidis. The rapid-onset fever, headache, neck stiffness, lethargy, and seizures fit acute meningitis, and meningococcal disease is a classic concern in this age group because people can be asymptomatic carriers and transmission occurs through respiratory droplets in crowded settings. Vaccination against the capsule types reduces risk, but exposure can still occur.

Streptococcus pneumoniae is a common meningitis cause overall, particularly in older adults or those with certain risk factors, so it’s less likely the top culprit in this healthy 18-year-old. Haemophilus influenzae type b used to be a frequent cause in children before widespread vaccination, but its incidence has dropped significantly in teens and adults. Listeria monocytogenes tends to affect neonates, older adults, pregnant individuals, or those with compromised immunity, not typically a healthy young adult.