Neisseria meningitidis is a Gram-negative, oxidase-positive, aerobic diplococcus of the family Neisseriaceae. It is an exclusive pathogen in humans, carried asymptomatically in the nasopharynx by 5%–10% of adults in non-epidemic periods. The bacterium can be either structurally encapsulated or not encapsulated. Capsule polysaccharide expression plays a key role in meningococcal pathogenesis and is the basis for the major serogrouping. In total, 13 serogroups of N. meningitidis have been reported, but only six serogroups (A, B, C, W135, X, and Y) cause almost all worldwide life-threatening disease.1,2 N. meningitidis strains that cause invasive disease are almost always encapsulated, which helps survival of the bacteria during invasive disease and promotes transmission as well as protection from antibodies and phagocytic cells.2…show more content… meningitidis transmissions.3 However, less than 1% of individuals who acquire carriage go on to develop meningococcal disease. The balance between carriage of the organism and the development of the disease after acquisition is affected by N. meningitidis characteristics and host and environmental factors including age, functional or anatomic asplenia, host immune deference mechanisms and the bacterial virulence
