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Neisseria meningitidis, also simply known as meningococcus is a gram-negative bacterium best known for its role in meningitis.
Clinical Presentations
Meningitis is the most well publicised condition. Whilst a non-specific illness initially, this can rapidly progress through fever, headache and neck stiffness to coma and death. The mortality is approximate 10% of cases. Suspicion of meningitis is a medical emergency and immediate medical assessment is recommended.
Septicaemia ("blood poisoning") has received much less public attention, but has been linked to infant deaths. Whilst there may be an absence of the classical meningitis symptoms, the presence of a non-blanchable purpuric rash is easly ignored by those not aware of its significance. Septicaemia carries an approximate 50% mortality rate over a few hours from inital onset. Anyone developing a rash that does not turn white ("non-blanching") if pressed with a glass in encouraged to attend a hospital casualty department as soon as possible.
UK policy is that any General Practitioner doctor seeing a suspected case of meningococcus meningitis or septicaemia should give intravenous antibiotics (benzylpenicillin) whilst hospital admission is sought. The possible reduction in subsequent microbiological confirmation of infection, due starting treatment before testing, is offset by the reduced mortality.
Not all cases of a purpura-like rash are due to septicaemia, but the other causes also need prompt investigation (eg ITP, a platelet disorder).
Strains
There are many strains of meningococcus, clinically the most important are A, B, C and W135:
- A - occurs most often in sub-sahara Africa and vaccination is recomended prior to travel with the Men A&C vaccine.
- B - is the most lethal form, comprising 40% of UK cases. There is no vaccination currently available for this strain.
- C - caused approxiamately 60% of UK cases before the introduction of successful vaccination programme for infants. Previously the unconguted C component of Men A&C was ineffective in those under 2 years. The development of a conjugated form (Men C conj) was needed to provoke infant immunity.
- W135 - is particularly a problem for those undergoing annual pilgramage to Mecca. It is a requirement of Saudi Arabia that all those intending to go on Hajj have a certificate of Men W135 vaccination.
Those with impaired immunity may be at particular risk of meningococcus, eg those with nephrotic syndrome or splenectomy. In asplenia (removed or non-functioning spleen), vaccination is performed according to protocols.
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