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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


Common name for Neisseria meningitidis.
References in periodicals archive ?
We conducted this study to determine whether W meningococci belonged to a hyper-virulent genetic lineage of the ST-11 clonal complex (CC).
The data from this co-culture model system suggest that meningococci may undergo important transcriptional changes when they enter the human nasopharynx and encounter resident bacterial populations.
However, past experience has shown that meningococci belonging to serogroups C, W, or X can cause substantial epidemics (8-10); therefore, continuing surveillance will be needed to determine how the epidemiology of meningococcal disease in the meningitis belt of Africa is changed by the successful introduction of PsA-TT (11).
Persistence of neurological manifestations, absence of meningococci on CSF gram staining and presence of the eschar pointed to rickettsial etiology, with positive OX-2 titres on Weil-Felix test.
Vaccines covered by the Agreement include those for the prevention of diseases caused by Group A streptococci, Group B streptococci, Pneumococci, Group B meningococci, anthrax bacilli and urinary tract infection (UTI) associated E.
national campaign to immunize 15 million children under age 17 with a monovalent conjugate vaccine against serogroup C meningococci resulted in an 81 percent overall decline in cases and 90 percent reduction in deaths from meningococcal serogroup C disease within one year.
The laboratory was the first in the world to automate the multi-locus sequence typing (MLST) procedure that is now used routinely in Scotland as a tool for the genotypic characterization of meningococci.
Cluster of serogroup W135 meningococci, southeastern Florida, 2008-2009.
Meningococcemia is so much more deadly than meningitis because, like all gram-negative bacteria, the meningococci incorporate in their cell walls a poisonous molecule called endotoxin.
For example, type B meningococci account for approximately one half of the 2,600 yearly cases of meningococcal disease in the United States and there have been epidemic outbreaks in Oregon and Washington.
meningitidis serogroups A and C is thought to have led to a selective increase in the incidence of meningococci of other serogroups, thereby resulting in a changed profile of meningococcal disease (10-12).