CLASSIFICATION

There are two accepted groups of species and some additional species. The two groups are differentiated on the basis of pigmentation, whether the colonies are transluscent or opaque and whether the strains are saccharolytic or not. Within the groups the species are subdivided on the basis of ability to produce acid from some carbohydrates, reduction of nitrate, requirement for added CO2 and ability to grow on nutrient agar.

BIOCHEMISTRY

They frequently do not catabolise many carbohydrates and some species are asaccharolytic. Glucose is the only carbohydrate used by the saccharolytic species and is degraded by a combined Entner-Doudoroff and pentose phosphate pathway. Amino acids can be used as sources of carbon and energy via the tricarboxylic acid cycle. They are not motile.

The chromosome of N. gonorrhoea consists of a single circular DNA molecule with a molecular weight of 9.8 x 108 but this may be an underestimate. Neisseria species have been shown to carry many plasmids.

Unlike E. coli and related bacteria, the lipopolysaccharide (LPS) of Neisseria strains do not have the repeating O-antigen subunits and thus cannot be subdivided in this way. However, their LPS is antigenic, which shows antigenic variation. Serogrouping of the Neisseria strains is based on antigenic differences in the capsular polysaccharides. Currently there are recognized the serogroups A, B, C, H, I, K, L, X, Y, Z, W135 and 29E160. The fimbrial antigens (pili) may also be used for serological classification.

NORMAL FLORA

Apart from N. gonorrhoea and N. menigititis the non-pathogenic Neisseria sp. are part of the normal flora of the human oro- and nasopharynx. They also form the commensal flora of these sites of animals.

Enteric Infections:
N. gonorrhoea can cause localized infections of the rectum.
Extraintestinal Infections:
N. gonorrhoea is the cause of gonorrhoea causing infections of the epithelial cells of mucosal surfaces of the urethra, cervix, rectum and eye. Untreated gonorroea can lead to disseminated infections including the bacteraemic spread.
N. menigititis may also be part of the normal flora of the human oro- and nasopharynx giving a high carriage rate. Strains belonging to serogroup A are frequently associated with epidemics of meningitis while strains of serogroups B, C, and W135 appear to cause sporadic outbreaks.
Animal Infections:
There do not appear to be any animal infections. Some animal species appear to carry in their throats certain Neisseria species; N. canis in dogs, N. cuniculi in rabbits and N. macacae. in rhesus monkeys.

In uncomplicated gonorrhoea, presumptive diagnosis can be made by the microscopic detection of typical diplococci within morphonuclear leukocytes. The cultivation on selective media of oxidase-positive Gram-negative diplococci is the most important means of diagnosis, from the sites chosen. N. gonorrhoea are fastidious and require CO2-enriched atmosphere for primary isolation.

They are not able to survive outside bodies of humans or animals

No industrial uses have been reported.

Currently there are no vaccines to prevent gonorroea.
Vaccines to prevent outbreaks of menigitis are available against serogroups of N. menigititis A, C, AC, ACYW135.
Vaccines against serogroup B of N. menigititis are not available.

Neisseriaceae

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