Neisseria meningitidis, often referred to as
meningococcus, is a
gram negative bacterium that can cause
meningitis and other forms of
meningococcal disease such as
meningococcemia, a life-threatening
sepsis. The bacterium is referred to as a
coccus because it is round, and more specifically,
diplococcus because of its tendency to form pairs. About 10% of adults are carriers of the bacteria in their
nasopharynx. As an exclusively human pathogen it is the main cause of bacterial meningitis in children and young adults, causing developmental impairment and death in about 10% of cases. It causes the only form of bacterial
meningitis known to occur
epidemically, mainly in Africa and Asia.
N. meningitidis is spread through saliva and respiratory secretions during coughing, sneezing, kissing, and chewing on toys. It infects the cell by sticking to it with long thin extensions called
pili and the surface-exposed proteins Opa and Opc and has several virulence factors.