Meningococcal and Gonococcal Infections

• Neisseria

  • N. gonorrhoeae

  • N. meningitidis (contains a polysaccharide capsule)

  • Non-pathogenic species exist in upper respiratory and alimentary tracts

    • Non-motile gram –ve cocci existing as two cocci joined together forming a bean shaped structure (diplococci)

    • Aerobes – pathogenic species prefer ↑ [CO₂]

    • Oxidase +ve, catalase +ve, most ferment glucose

Differentiating Neiserria from other genera:

The main point here is:

• Neisseria can be differentiated from other members of Neisseriaceae family biochemically: i.e.: catalase +ve, oxidase +ve, and most ferment glucose

Identifying Neisseria species:

The main point here is:

• Different species of the Neisseria genus form different colonies and have different morphologies:

  • N. gonorrhoeae and N meningitidis have non-pigmented, non-haemolytic, glistening, mucoid, raised, convex, elevated colonies

  • Other have: yellow pigmentation, opaque, brittle, wrinkled colonies.

  • Environmentally fragile: so inoculate immediately in pre-warmed agar plates

Category: Microbiology Notes