Description

Bacterial infection of the meninges

Epidemiology

• Predominant age: neonates, infants, and elderly
• Predominant sex: male = female

Varies by age and pathogen

• 18 to 34 years 0.66/100,000
• 35 to 49 years 0.95/100,000
• 50 to 64 years 1.73/100,000
• ≥65 years 1.92/100,000
• Group B Streptococcus: 0.25/100,000
• Neisseria meningitidis: 0.19/100,000
• Haemophilus influenzae: 0.08/100,000
• Listeria monocytogenes: 0.05/100,000

Prevalence
15,000 to 25,000 cases occur annually in United States.

Etiology and Pathophysiology

Bacterial infection causes inflammation of the meninges. Age and likely pathogens guide empiric antibiotic choice. Tailor therapy to culture results whenever possible:

• Community-acquired bacterial meningitis is most commonly due to S. pneumoniae (50%) and N. meningitidis (30%).
• Nosocomial or postsurgical meningitis occurs after manipulation of the central nervous system (CNS) space allowing for entry of pathogens.
• Newborns (<2 months)
  • Group B Streptococcus, Escherichia coli, L. monocytogenes
• Infants and children
  • S. pneumoniae, N. meningitidis, H. influenzae
• Adolescents and young adults
  • N. meningitidis, S. pneumoniae
• Immunocompromised adults
  • S. pneumoniae, L. monocytogenes, gram-negative bacilli such as Pseudomonas aeruginosa
  • Mixed bacterial infection in <1% of cases
• Older adults
  • S. pneumoniae 50%, N. meningitidis 30%, L. monocytogenes 5%
  • 10% gram-negatives bacilli: E. coli, Klebsiella, Enterobacter, P. aeruginosa

Genetics
Some Native American populations appear to have genetic or acquired susceptibility to invasive disease.

Risk Factors

• Immunocompromised, alcoholism, diabetes, chronic disease
• Neurosurgical procedure/head injury, close living quarters
• Neonates: prematurity, low birth weight, premature rupture of membranes, maternal peripartum infection, and urinary tract abnormalities
• Abnormal communication between nasopharynx and subarachnoid space (congenital, trauma), dural fistula
• Parameningeal source: otitis, sinusitis, mastoiditis; trauma: skull fracture
• Adults age >65 years, immunocompromised patients, and pregnant women are at risk for listeriosis.
• Complement component deficiencies C3, C5 to C9, properdin, factor H, and factor D
• Functional or anatomic asplenia
• Patients taking eculizumab are at increased risk for meningococcal disease.

General Prevention

• Consider CSF fistula in cases of recurrent meningitis.
• Aseptic techniques for head wounds or skull fractures
• Meningitis caused by H. influenzae type B has decreased 55% with routine vaccination.
• Conjugate vaccines against S. pneumoniae may reduce the burden of disease in childhood.
• Chemoprophylaxis for close contacts of meningococcal meningitis patients

Commonly Associated Conditions

Factors associated with a worse prognosis:

• Alcoholism, old age, infancy, diabetes mellitus, multiple myeloma, head trauma, seizures, immunocompromised
• Coma, sepsis, sinusitis