meningococcus

Last reviewed 06/2021

Meningococcal disease occurs as a result of infection with the bacterium Neisseria meningitides (1). The meningococcus is:

• a gram negative coccus
• globally endemic with periodic epidemics
• the most common cause of pyogenic meningitis in the UK
• predominantly a pathogen of children and young adults
• most often seen in crowded communities such as army barracks

During epidemics close contacts of infected cases should be offered chemoprophylaxis.

Meningococci are divided into antigenically distinct groups according to the chemical composition of the polysaccharide capsule of the bacteria (2).

• there are at least 13 serogroups, of which group B and C are the most common in the UK
• but with the introduction of the Men C vaccine, serogroup C disease has reduced substantially with just 10 cases reported in the year 2009 (2)
• other less common serogroups include A, Y, W135, 29E and Z.

Meningococcal bacteria colonise the nasopharynx of humans and are frequently harmless commensals

• between 5% and 11% of adults and up to 25% of adolescents carry the bacteria without any signs or symptoms of the disease
• invasive disease does not develop in established meningococcal carriers (3)
• transmission is by aerosol, droplets or direct contact with respiratory secretions of someone carrying the organism. Transmission usually requires either frequent or prolonged close contact
• there is a marked seasonal variation in meningococcal disease, with peak levels in the winter months declining to low levels by late summer
• incidence of meningococcal disease is highest in children aged one to five years followed by infants under one year of age
• next highest risk group is young people aged 15 to 19 years.

Immunisation is available against strains A and C of this bacteria, however strain B is the most often implicated in meningococcal meningitis.

Meningococcal infection may present as

• meningitis - 15% of cases
• septicaemia - 25% of cases
• a combination of both meningitis and septicaemia - 60% of cases (4)
• less commonly, individuals may present with pneumonia, myocarditis, endocarditis, pericarditis, arthritis, conjunctivitis, urethritis, pharyngitis, and cervicitis (1)

Click here for an example image of meningoccal septicaemia

Reference:

• (1) Department of Health (DH) 2010. Immunisation against infectious disease - "The Green Book". Chapter 22- Meningococcal.  
• (2) Meningitis Research Foundation 2010. Lessons from research for doctors in training
• (3) Health Protection Agency (HPA) 2011. Guidance for public health management of meningococcal disease in the UK   
• (4) NICE (June 2010). Bacterial meningitis and meningococcal septicaemia Management of bacterial meningitis and meningococcal septicaemia in children and young people younger than 16 years in primary and secondary care