Neisseria meningitidis

Main points here are:

• Causes meningococcal meningitis, human transmission via aerosols (e.g.: coughing, sneezing).

• Colonies found in nasopharynx (attaching to microvilli of non-ciliated columnar epithelial cells)

• Infection by N.meningitidis ≫ bacteraemia (septicaemia) + acute inflammation of subarachnoid space (CSF is cloudy). Sometimes bacteraemia doesn’t lead to CNS involvement ≫disseminated IV coagulation + shock.

Most at risk

• Children <>

Symptomology

• Sore throat, headache, muscle aches, pains, chills, drowsiness. Signs include: fever, stiff neck, photophobia, irritations, petechial rash (peculiar to meningococcal meningitis)

Confirmation of Meningococcal Meningitis:

• CSF culture, blood culture. Requires special conditions: cultures show ↑ no. of gram –ve diplococci

Pathogenesis

• Survival on mucosal surface improved by IgA1 protease, contains polysaccharide capsule improving survival in serum (inhibits phagocytosis).

• Polysaccharide capsule variable: therefore divided into serogroups:

  • A, B, C, W₁₃₅, Y

  • Australia: B most common. Group B polysaccharide doesn’t cause immune response so vaccine not possible.

  • Vaccines available against A, C, W₁₃₅, Y. 2 yrs protection. Cannot be given to children <>

Treatment

• Mortality is 85-100% in untreated cases, 10% in treated cases.

• Penicillin, cephalosporins, erythromycin + chloramphenicol. Type give depends on drug allergies, local resistance patterns etc.

• Prophalyaxis important: chemotherapeutic (drugs) or vaccination.

Category: Microbiology Notes