Which organism is the most common cause of meningococcal meningitis?

Which organism is the most common cause of meningococcal meningitis?

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

Answer: (A)

Neisseria meningitidis is the organism that causes meningococcal meningitis. This Gram-negative diplococcus typically resides in the nasopharynx and can spread through respiratory droplets, invading the bloodstream and seeding the meninges. The term “meningococcal” literally points to this organism as the etiologic agent. In outbreaks or close-contact settings, such as dormitories or military barracks, it’s the classic cause of meningitis that can present with sudden fever, immune response in the CSF, and sometimes purpura from meningococcemia. Among the other organisms listed, Streptococcus pneumoniae is the most common overall cause of bacterial meningitis in adults, Haemophilus influenzae used to be a common cause but has become less frequent with vaccination, and Listeria monocytogenes tends to affect neonates, older adults, and immunocompromised individuals. However, the question asks about meningococcal meningitis specifically, so Neisseria meningitidis is the best answer.

Neisseria meningitidis is the organism that causes meningococcal meningitis. This Gram-negative diplococcus typically resides in the nasopharynx and can spread through respiratory droplets, invading the bloodstream and seeding the meninges. The term “meningococcal” literally points to this organism as the etiologic agent. In outbreaks or close-contact settings, such as dormitories or military barracks, it’s the classic cause of meningitis that can present with sudden fever, immune response in the CSF, and sometimes purpura from meningococcemia.

Among the other organisms listed, Streptococcus pneumoniae is the most common overall cause of bacterial meningitis in adults, Haemophilus influenzae used to be a common cause but has become less frequent with vaccination, and Listeria monocytogenes tends to affect neonates, older adults, and immunocompromised individuals. However, the question asks about meningococcal meningitis specifically, so Neisseria meningitidis is the best answer.