These are Gram-negative, oxidase-positive, catalase-positive nonsporing non-acid fast cocci or plump rods (generally 0.6-1.0µm in diameter or up to 1.0x2.0-3.0µm). The cocci often occur in pairs with their adjacent sides flattened, giving the typical "kidney-bean" arrangement of diplococci. They are not motile. They are aerobes, although a few may be microaerophilic or facultative anaerobes, nonhalophylic with optimal growth around 37°C. Some species are pigmented. Some species will not grow on simple bacteriological media and may require blood or ascitic fluid for growth as well as increased CO2 pressure. They have a functioning tricarboxylic acid cycle and can use the Entner-Doudoroff and pentose phosphate shunt. Although the Embden-Meyerhof (EM) enzymes are present, the EM pathway is not extensively used and probably not at all under aerobic conditions. Acid is formed from glucose by some strains and some can ferment other sugars. The base composition of the DNA is 49-56 mol%GC. Neisseria is the type genus.

Genera

Neisseria: These are currently divided into two groups on the basis of pigmentation and sugar metabolism. There is a possible third group, Branhamella catarhalis, which shows some relationships with groups 1 and 2 but differs in a number of features including the ability to hydrolyse tributyrin, reduce nitrate and produce DNAase.

Group 1: These strains are non-pigmented and form transluscent colonies. They are generally asaccharolytic. The species include: N. cinerea, N. gonorrhoeae, N. gonorrhoeae subsp. kochii, N. lactamica, N. meningitidis and N. polysaccharea.

Group 2: These strains are yellow-pigmented and form opaque colonies. They are generally saccharolytic. The species include: N. mucosa, N. sicca and N. subflava and the asaccharolytic species N. flavescens.

Group 3: The strains of the species Branhamella catarhalis are considered by some taxonomists to form a possible third group, due to relationships with both groups, but having distinct features.

Uncertain Group: The three animal species are of uncertain taxonomic status. They are: N. caviae, N. cuniculi and N. ovis.

Kingella:

Eikenella:

Simonsiella:

Alysiella:

CDC group EF-4:

CDC group M-5:

Species Profiles

Neisseria

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