Neisseria meningitidis

Neisseria MENINGITIDIS (Meningococcus)


Non-motile Gram-negative diplococci with fastidious growth requirements: capnophilics; capsulate.


  • Meningitis
  • Septicemia in absence of meningitis
  • Chronic meningococcal arthritis


Human pathogens; no animal reservoir. This carried in pharynx. Carriage rate in population increases during epidemics. Droplet spread N. meningitidis has several immunologically distinct capsular types (A, B, C).

Laboratory Diagnosis

Sample collection:

  1. Cerebrospinal fluid
  2. Blood for culture in septicaemia
  3. Aspirate from skin leasion or pus from infected joint
  4. Swab from nasopharynx and throat to detect carriers

Transportation of sample:

Transport sample as early as possible. Never refrigerate the sample. It should be kept at 35º-37ºc

Processing of the sample:

  1. C.S.F. sample is collected in two sterile test tubes:
    1. One for culture and
    2. Other for cell count, microscopy and biochemistry.
  2. The smears are prepared directly from the sample if it is turbid. If slight sloudy,centrifuge the sample and sediment is used for preparation of smears and culture

Methods for identification of organism:

 Direct methods:

  1. Gram staining:
    • Gram-negative diplococcic with adjacent sides flattened cells often in pairs and chains and some are seen intracellular in polymorphoneuclear cells.
  2. Culture:
    • Culture media: chocolate agar
      • Grow well at 37°C in moist atmosphere containing 5-10% CO2
  1. Biochemical reactions:
    • Oxidase test positive
    • Sugar fermentation test:
      • Glucose: produce acid without gas
      • Maltose: produce acid without gas
  2. Antibiotic sensitivity test

Indirect methods:

  • Slide agglutination test
  • Coaglutination test and
  • Latex agglutination test