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Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

The most probable causative organism is age dependent:

  • neonates
    • can be
      • early - occurring during the first week of life, primary mode of infection is by vertical transmission (mother to child) through the birth canal
      • late - occurring between the second and sixth week, transmission is nosocomial or from person to person
    • causative agents include;
      • Streptococcus agalactiae (group B streptococcus)
      • E.coli and gram negatives
      • Streptococcus pneumoniae
      • Listeria monocytogenes
  • children (beyond neonatal age)
    • Haemophilus influenzae type b
      • since the introduction of the vaccine H. influenza type b in 1990s, this pathogen is no longer a major cause of bacterial meningitis n children
    • Neisseria meningitidis – Meningococcus
      • most N. meningitidis colonisations are asymptomatic, but occasionally the organism invades the bloodstream (usually within a few days of a susceptible person acquiring the organism) to cause meningococcal disease which includes
        • bacterial meningitis (15% of cases)
        • septicaemia (25% of cases)
        • a combination of the two syndromes (60% of cases)
      • tuberculosis
    • Streptococcus pneumoniae - Pneumococcus
  • adults
    • Streptococcus pneumoniae – Pneumococcus
    • Neisseria meningitidis – Meningococcus
      • mostly seen in adolescents and mostly caused by serogroup B
      • incidence has declined in the past decade
    • Listeria monocytogenes
      • commonly associated with old age and immunocompromised state
    • Haemophilus influenza
    • Staphylococcus aureus
  • immunocompromised patients
    • Pneumococcus
      • predisposing conditions include: splenectomy or hyposplenic state, chronic kidney or liver disease, HIV, alcoholism, diabetes
    • Haemophilus influenza
      • seen in: diabetes, alcoholism, splenectomy or asplenic state, multiple myeloma
    • Listeria monocytogenes
      • associated with elderly patients (>60 years), in acquired immunodeficiencies (diabetes, cancer), use of immunosuppressive drugs


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