A species of aerobic, Gram-negative, diplococci shaped bacteria assigned to the phylum Proteobacteria. This species is catalase and oxidase positive, non-hemolytic, non-pigmented, does not reduce nitrate or nitrite, does not synthesize polysaccharides, grows on blood, chocolate, or Muller-Hinton agar, and produces acid from glucose and maltose but not fructose, sucrose, mannose, or lactose. N. meningitidis, known commonly as meningococcus, is the causative agent of cerebrospinal meningitis, but is also associated with other human infections, but can be commensal in the oropharynx and nasopharynx of carriers.

A species of gram-negative, aerobic BACTERIA. It is a commensal and pathogen only of humans, and can be carried asymptomatically in the NASOPHARYNX. When found in cerebrospinal fluid it is the causative agent of cerebrospinal meningitis (MENINGITIS, MENINGOCOCCAL). It is also found in venereal discharges and blood. There are at least 13 serogroups based on antigenic differences in the capsular polysaccharides; the ones causing most meningitis infections being A, B, C, Y, and W-135. Each serogroup can be further classified by serotype, serosubtype, and immunotype.

Any bacterial organism that can be assigned to the species Neisseria meningitidis.

Gram-negative, aerobic bacteria; a commensal and pathogen only of humans, and can be carried asymptomatically in the nasopharynx; when found in cerebrospinal fluid it is the causative agent of cerebrospinal meningitis; also found in venereal discharges and blood; there are at least 13 serogroups based on antigenic differences in the capsular polysaccharides; the ones causing most meningitis infections being A, B, C, Y, and W-135; each serogroup can be further classifed by serotype, serosubtype, and immunotype.