Description

Bacterial infection of the meninges resulting in inflammation, pain, and systemic illness

Epidemiology

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

Incidence
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: 0.19/100,00
• Haemophilus influenzae type B: 0.08/100,000; Listeria monocytogenes: 0.05/100,000

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

Etiology and Pathophysiology

Community-acquired bacterial meningitis is most commonly due to Streptococcus pneumoniae (50%) and N. meningitidis (30%). Nosocomial or postsurgical meningitis occurs after manipulation of the central nervous system (CNS); 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-negative bacilli: E. coli, Klebsiella, Enterobacter, P. aeruginosa

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

Risk Factors

Those who are at risk include household or close contacts of case patients; immunocompromised (including HIV, asplenia, or patients taking eculizumab, ravulizumab), alcohol use disorder, diabetes, or chronic disease; neurosurgical procedure/head injury, close living quarters (dormitories or military barracks), and work exposures; neonates: prematurity, low birth weight, premature rupture of membranes, maternal peripartum infection, and urinary tract abnormalities; anatomical abnormality of nasopharynx and subarachnoid space (congenital, trauma), dural fistula; parameningeal source: otitis, sinusitis, mastoiditis, skull fracture; elderly, immunocompromised, and pregnant patients are at risk for listeriosis; complement deficiencies, properdin, factor H, and factor D

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: alcohol use disorder, elderly, infancy, diabetes mellitus, multiple myeloma, head trauma, seizures, immunocompromised, coma, sepsis, sinusitis