Bacterial Meningitis
Acute bacterial meningitis: Life-threatening acute purulent infection of the leptomeninges (pia mater, arachnoid mater) and the subarachnoid space, characterized by meningism and neutrophilic CSF pleocytosis.
Bacterial Meningitis
- Nasopharyngeal colonization by encapsulated pathogen
- $\rightarrow$ Secretion of IgA proteases enables mucosal attachment and invasion
- $\rightarrow$ Intravascular survival via antiphagocytic polysaccharide capsule
- $\rightarrow$ Crossing of the blood-brain barrier via cerebral capillaries or choroid plexus
- $\rightarrow$ Rapid bacterial replication in the subarachnoid space (low baseline complement/antibodies)
Read this in Bacterial meningitis and encephalitis
What our notes say
- Acute bacterial meningitis: Life-threatening acute purulent infection of the leptomeninges (pia mater, arachnoid mater) and the subarachnoid space, characterized by meningism and neutrophilic CSF pleocytosis. (Bacterial meningitis and encephalitis)
- Bacterial meningitis: stat ceftriaxone and lumbar puncture (Treatment of Infectious Disease: 5-case clinical quiz)
- Depressed GCS, focal deficits, or seizures signal cerebral malaria, bacterial meningitis, or intracranial tuberculoma/toxoplasmosis. (Approach to fever)
- | Acute bacterial meningitis | Fever, severe headache, photophobia, neck stiffness | Lumbar puncture: cloudy CSF, neutrophilia | (Approach to fever)
- Bacterial Meningitis: Both cause headache, fever, and neck stiffness. (HIV and opportunistic infections)
- Look-alike conditions: Typhoid fever, bacterial meningitis, severe anaemia from other causes, viral hepatitis. (Malaria, including severe malaria)
Study material on Bacterial Meningitis
- Bacterial meningitis and encephalitis
- Headache and red flags
- Approach to fever
- CNS PATHOLOGY
- Streptococcus Classification, S. pyogenes, Rheumatic Fever, AGN
- Neurological history and examination
- Raised intracranial pressure
- Streptococcus pneumoniae: Characteristics, Pathogenesis, and Management
- Weekly Year 2: Microbiology Exam - June 12, 2026 (Section A: MCQs)
- Weekly Year 2: Microbiology Exam - May 29, 2026 (Section A: MCQs)
Practice questions on Bacterial Meningitis
Which of the following is NOT a most important cause of acute bacterial meningitis in adults?
- Streptococcus pneumoniae
- Neisseria meningitidis
- Haemophilus influenzae type b
- Listeria monocytogenes
Answer: C. While Haemophilus influenzae type b (Hib) is a significant cause of meningitis, it is more common in unvaccinated children. In adults, Streptococcus pneumoniae and Neisseria meningitidis are the most common bacterial causes of meningitis.
Which cephalosporin has the best CNS penetration and is used for bacterial meningitis?
- Cephalexin
- Cefazolin
- Ceftriaxone
- Cefadroxil
- and has a long half-life allowing once or twice-daily dosing.
Answer: C. Ceftriaxone is a third-generation cephalosporin with excellent CSF penetration, especially in inflamed meninges. It's effective against common meningitis pathogens (S. pneumoniae, N. meningitidis, H. influenzae) and has a long half-life allowing once or twice-daily dosing. ---
The most common cause of acute bacterial meningitis in adults is
- Listeria monocytogenes
- Haemophilus influenzae
- Streptococcus pneumoniae
- Neisseria meningitidis
- Mostly unchanged in early disease
Answer: C. S. pneumoniae (pneumococcus) is the leading cause of bacterial meningitis in adults and elderly, accounting for approximately 50% of cases. It also causes pneumonia, otitis media, and sinusitis.
Which of the following is not most important cause of acute bacterial meningitis?
- Streptococcus pneumoniae
- Neisseria meningitides
- Streptococcus pyrogens
- Hemophilus influenza
- .
Answer: C. S. pyogenes (Group A Strep) rarely causes meningitis. The three most common causes of bacterial meningitis are S. pneumoniae (most common overall), N. meningitidis (especially in young adults), and H. influenzae type b (reduced since Hib vaccine).
Streptococcus pneumoniae is the most common cause of community-acquired bacterial meningitis in adults.
- A) Streptococcus pneumoniae
- B) Neisseria meningitidis
- C) Haemophilus influenzae type b
- D) Listeria monocytogenes
Answer: A. While Neisseria meningitidis and Haemophilus influenzae type b are significant causes of bacterial meningitis, Streptococcus pneumoniae is considered the leading cause of bacterial meningitis in adults in many parts of the world, particularly in developed countries.
The most common cause of acute bacterial meningitis in adults is Streptococcus pneumoniae.
- A) Streptococcus pneumoniae
- B) Neisseria meningitidis
- C) Haemophilus influenzae
- D) Listeria monocytogenes
Answer: A. In adults, Streptococcus pneumoniae is the leading cause of community-acquired bacterial meningitis. While Neisseria meningitidis and Haemophilus influenzae are also significant pathogens, S. pneumoniae is generally considered the most common in this age group.