Disease caused by Neisseria meningitidis

 Neisseria meningitidis.


  • It is a gram negative, non-motile cocci arranged in pairs called as diplococci.
  • Neisseria are aerobic, non-sporulating, oxidase positive cocci.
  • Neisseria meningitidis causes cerebrospinal fever that is Meningococcal meningitis.
Neisseria meningitidis
Neisseria meningitidis

1. Morphological characters

  • They are gram negative,spherical shape cocci with flattened adjacent side.
  • Its size ranges from 0.6-0.8 micrometer.
  • Its size,shape and staining properties changes as the incubation period increases.
  • Fresh culture cells are capsulated and as the culture becomes old its capsule disappears.

2. Cultural characters

  • Meningococci requires enriched media for its growth.
  • The growth media should be enriched with blood or serum.
  • Selective media like blood agar, chocolate agar, Mueller-Hinton starch casein agar are commonly used.
  • The optimum temperature required for its growth is 36°C and optimum pH is 7.5-7.6
  • The colonies are small in size bluish grey coloured and convex in elevation.

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