Gram negative diplococci, causing meningitis and septicaemia. Sometimes bone/joint infection. Neisseria (not meningitidis) responsible for ophthalmia neonatorum.

Main serogroups:

• A – responsible for epidemics of meningitis across “Meningitis belt” of Sub-Saharan Africa, until Men A monovalent vaccine introduced in 2010 (still epidemics, but due to other serotypes). Hajj also triggers outbreaks.
• B – 4 component vaccine introduced in 2015 to deal with B being the most common cause of invasive meningococcal disease since introduction of MenC vaccine. Based on vaccine developed for New Zealand epidemic.
• C – used to be most common cause of invasive meningococcal disease in UK until vaccine introduced. So successful that early dose was dropped from routine schedule, although later resurgence in older children and young people, so teenage booster and university catch up programme introduced.

Clinically, notorious for rapidly evolving, often fatal septicaemia with non blanching rash and limb ischaemia. Curiously, meningococcal meningitis, on the other hand, is the most benign of the various causes of bacterial meningitis. Can be mixed picture, ranging from a few petechial spots only with an otherwise typical meningitis presentation, or else meningococcal septicaemia with neck stiffness, where presence of meningitis is actually a good prognostic sign.

Exquisitely sensitive to antibiotics. Meningitis epidemics in Africa treated with single IM dose ceftriaxone!!! Nasal carriage is the reason for spread, so prophylaxis for close contacts important.