Bacterial Meningitis


Bacterial meningitis is bacterial infection of the cerebrospinal fluid within the subarachnoid space. It can be broadly divided into acute or chronic meningitis and community‐acquired or healthcare‐associated (nosocomial) meningitis. Each entity is associated with a particular pattern of infecting organisms, presentation, management and outcome. Acute bacterial meningitis is the commonest and, arguably, the most important. The epidemiology of acute bacterial meningitis is evolving worldwide, primarily driven by changing immunisation schedules. A wide variety of organisms have been associated with acute bacterial meningitis, but the majority of cases are caused by a handful of organisms (Streptococcus pneumoniae, Neisseria menigitidis, Group B streptococcus, Haemophilus influenzae and Listeria monocytogenes). Chronic bacterial meningitis is less common and is usually caused by Mycobacterium tuberculosis. Bacterial meningitis is a medical emergency requiring prompt diagnosis and treatment as mortality approaches 100% if left untreated. Even with treatment there is a significant mortality rate and long‐term neurological sequelae are common.

Key Concepts:

  • The frequency and aetiology of bacterial meningitis varies according to multiple factors but most importantly patient age, geographical region and social setting.

  • The incidence and commonest aetiological agents of bacterial meningitis have altered over the last two decades with the introduction of Hib, pneumococcal and menigococcal vaccines.

  • The triad of fever, meningitis and altered mental state is not universally present but the absence of any of these features usually excludes a diagnosis of meningitis.

  • Early antibiotics administration is crucial to achieving a good outcome.

  • CSF examination is the most valuable diagnostic investigation.

  • Empiric treatment for tuberculous meningitis should be commenced on clinical suspicion alone and should not wait for microbiological confirmation.

  • Coadministration of glucocorticoids with antituberculous therapy reduces both morbidity and mortality from TBM.

Keywords: bacterial meningitis; chronic; acute; pneumococcus; meningococcus; tuberculosis

Figure 1.

Pneumococcal meningitis. Brain tissue and subarachnoid space showing congested blood vessels, neutrophil polymorphs and cellular debris within the subarachnoid space.

Figure 2.

Pneumococcal meningitis. High‐power view of the surface of the brain. The leptomeninges are inflamed and yellow pus is evident beneath them.

Figure 3.

Pneumococcal meningitis. Gram stain of cerebrospinal fluid showing neutrophil polymorphs and Gram‐positive diplococci (pneumococci).



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How to Cite close
Hemsley, Carolyn, and McGregor, Alastair(Nov 2011) Bacterial Meningitis. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0002220.pub2]