meningococcus

meningococcus

Neisseria meningitidis, the bacterium that causes meningococcal meningitis in humans, the only natural hosts in which it causes disease. Meningococci are spherical, frequently occur in pairs, and are strongly gram-negative (see gram stain). They enter the nasal passage and may cause no symptoms (up to 30% of the population may harbour them between epidemics), or they may enter the bloodstream and produce the symptoms of meningitis.

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meningococcus [mə¦niŋ·gə¦käk·əs]

(microbiology)

Common name forNeisseria meningitidis.

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Meningococcus

A major human pathogen belonging to the bacterial genus Neisseria, and the cause of meningococcal meningitis and meningococcemia. The official designation is N. meningitidis. The meningococcus is a gram-negative, aerobic, nonmotile diplococcus. It is fastidious in its growth requirements and is very susceptible to adverse physical and chemical conditions.

Humans are the only known natural host of the meningococcus. Transmission occurs by droplets directly from person to person. Fomites and aerosols are probably unimportant in the spread of the organism. The most frequent form of host-parasite relationship is asymptomatic carriage in the nasopharynx.

The most common clinical syndrome caused by the meningococcus is meningitis, which is characterized by fever, headache, nausea, vomiting, and neck stiffness and has a fatality rate of 15% (higher in infants and adults over 60). Disturbance of the state of consciousness quickly occurs, leading to stupor and coma. Many cases also have a typical skin rash consisting of petechiae or purpura. See Meningitis