Neisseria meningitidis

Neisseria meningitidis

N.meningitidis is a Gram-negative coccus (round shape) that is the major cause of bacterial meningitis worldwide. N.meningitidis is divided into 'serogroups' based on the differences in their surface molecules and how the immune system responds to this. Serogrouping of N. meningitidis is done by looking at the similarity of their capsule (a sugary layer around the cell). The most common serotypes found in diseases caused by N.meninigitidis are A, C, W, Y and B. Serogroup B strains (MenB) are particularly dangerous to young babies, and are responsible for the largest number of deaths in this age group. N. meningitidis colonise the throats of many people without ever causing disease. Meningitis only occurs when the bacteria infect the usually sterile membranes around the brain and spinal cord (meninges). The severity of N.meningitidis infection means  a lot of focus has traditionally been placed on developing vaccines against diseases caused by this bacteria.

N. meningitidis have many different charecteristics that adapt it to cause disease. These include: surface molecules for sticking to the host cell and surface receptors for taking up important nutrients. Many of these genes are subject to a process called phase variation, which means they can be switched on/off at random. In N. meningitidis, phase variation can help in evasion of the immune system.

1.) Neisseria meningitidis is one of the most common causes of bacterial meningitis, and is fatal in 50% of cases! 2.) Some N. meningitidis surface molecules undergo a process called 'phase variation' that help them to escape the immune system.


Scanning electron microscopy image of Neisseria meningitidis. You can see the characteristic pairs of bacteria forming a 'diplococcus'.


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