The Neisseria

Neisseria
Diseases and Important Properties:
1. N. meningitidis (meningococcus) has a prominent polysaccharide capsule that
enhances virulence by its anti-phagocytic action and induces protective
antibodies (Table 1). Meningococci are divided into at least 13 serologic groups
on the basis of the antigenicity of their capsular polysaccharides.
2. N. gonorrhoeae (gonococcus) has no polysaccharide. Gonococci have three
outer membrane proteins (proteins I, II, and III). Protein II plays a role in
attachment of the organism to cells.
3. Neisseriae are gram-negative bacteria and contain endotoxin in their outer
membrane. The endotoxin of N. meningitidis is a lipopolysaccharide (LPS)
similar to that found in many gram-negative rods, but the endotoxin of N.
gonorrhoeae is a lipooligosaccharide (LOS).
4. The growth of both organisms is inhibited by toxic trace metals and fatty acids
found in certain culture media, e.g., blood agar plates. They are therefore
cultured on "chocolate" agar containing blood heated to 80°C, which inactivates
the inhibitors. Neisseriae are oxidase-positive. This is an important laboratory
diagnostic test in which colonies exposed to phenylenediamine turn purple or
black as a result of oxidation of the reagent by the enzyme