Neisseria meningitidis

Neisseria meningitidis facts for higher education

Neisseria meningitidis

N. meningitidis (the meningococcus) is a Gram-negative bacterium, and a major causative agent of bacterial meningitis and severe sepsis. Meningococcal infections are a leading cause of morbidity and mortality worldwide, therefore understanding their molecular biology is crucial to develop therapeutics such as vaccines.

1 in 100,000 people will become infected with Neiserria meningitis every year, with the rate in children below the age of one at a staggering 30 cases per 100,000. N. meningitidis can be serotyped based on the similarity of their capsules. There are five serogroups of N. meningitidis commonly found colonising the human nasopharynx, these are: types A, C, W, Y and B. Distribution and carriage of these serogroups in the population varies over time, and understanding this distribution is important for informing meningococcal vaccination programmes. Serogroup B strains are particularly worrisome in children, and are one of the highest causes of mortality in this age group.


Scanning electron microscope image of N.meningitidis

This image shows the characteristic pairs of N. meninigitidis cells forming a diplococcus.

N. meningitidis usually colonise the nasopharyx of roughly 10% of healthy individuals, but can go on to cause meningitis if they infect the otherwise sterile, protective membranes around the brain and spinal cord (meninges) or septicaemia if they find their way into the blood. Symptoms of meningococcal meningitis specifically, include:  fatigue, fever, and headache but can rapidly progress to neck stiffness, coma and death. Meningococcal meningitis is the only form of the disease known to be transferred epidemically, usually in Africa and south east Asia. It is spread by coughing, sneezing, and expulsion of other respiratory secretions.

N.meningitidis have many different factors contributing to their ability to cause disease. These include the lipooligosaccharide component of its out membrane, which acts as a toxin against red blood cells (the main cause of septic shock and haemorrhage). You can find a useful review of the many molecular mechanisms contribution to the pathogenicity of Neisseria meningitidis here.

Here at UoL we're interested in the genetics of Neisseria meningitidis, and in particular the way it can switch expression of some of its genes on and off, a phenomenon known as phase variation. This process allows the bacterium to rapidly generate diversity in response to the hostile environment of the human host. Click here to read more about phase variation and take our tutorial investigating the contribution of phase variation to disease cause by N. meningitidis.

Neisseria meningitidis-
• The major causative agent of bacterial meningitis.
• Key virulence factors include the surface adhesins Opa and Opc, and an IgA protease.



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