Neisseria meningitidis
One-Sentence Definition
Neisseria meningitidis (meningococcus) is a Gram-negative diplococcus that colonizes the human nasopharynx and can invade to cause meningitis and fulminant sepsis, classified into capsule serogroups targeted by vaccines.
Taxonomy & Morphology
- Gram-negative kidney-bean diplococci
- Fastidious; grows on chocolate / special media
- Serogroups A, B, C, W, X, Y clinically important
- Related pathogen: N. gonorrhoeae (shared genetics, different niche)
Virulence Highlights
- Polysaccharide Capsule — antiphagocytic; vaccine antigen for most groups
- Lipooligosaccharide (endotoxin) — drives purpura fulminans
- Type IV pili — attachment; antigenic variation
- IgA protease; factor H binding protein (MenB vaccine target)
Clinical Syndromes
- Acute bacterial meningitis
- Meningococcemia ± Waterhouse-Friderichsen
- Chronic/occult bacteremia rarer
Diagnosis
- Blood/CSF Gram stain + culture; PCR panels common
- Rapid antigen tests variable by serogroup
- Isolate forwarding for typing/vaccine program surveillance
Treatment Notes (conceptual)
- Empiric meningitis regimens include meningococcal coverage pending ID
- Definitive therapy guided by AST (penicillin/ceftriaxone susceptibility patterns)
- Droplet isolation; prophylaxis for close contacts
AMR
- Reduced penicillin susceptibility via penA mosaic alleles (recombination) — classic Recombination in Bacterial Phylogenies species
- Emerging resistance concerns vary by region; surveillance essential
Genomics & Computational Notes
- Highly recombining; use recombination-aware methods / cgMLST
- Genomic epidemic typing for vaccine escape and hyperinvasive lineages (e.g., clonal complexes)
- Capsule switching via HGT tracked by WGS
Prevention
- Conjugate vaccines (ACWY) and MenB protein vaccines (Vaccination)
- Travel and outbreak campaign use-cases
Related Notes
- Bacterial Meningitis · Capsule · Vaccination · Antigenic Variation
- MOCs: MOC - Bacteriology · MOC - Diseases by System · MOC - Public Health & Epidemiology
Active Recall
- Which serogroups are covered by MenACWY conjugates?
- Why is recombination a major issue in meningococcal phylogenies?
- Name two clinical syndromes of invasive meningococcal disease.