Updated: 12/9/2015

Microbiology of Meningitis

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 Overview

Pathogens That Cause Meningitis by Age Group
Newborns
0-6 mo
Children
(> 6 months - < 6 years)
Adults
(18 - 40 years)
Seniors
(40 - 65 years)

IC

AC
  • GBS                      
  • E. coli
  • Listeria monocytogenes 
  • S. pneumoniae
  • N. meningitidis
  • H. influenzae
  • Enteroviruses (coxsackievirus, poliovirus, echovirus)
  • S. pneumoniae  
  • N. meningitidis
  • HSV-1
  • HSV-2
  • Enteroviruses (coxsackievirus, poliovirus, echovirus) 
  • S. pneumoniae
  • Listeria monocytogenes
  • S. pneumoniae
  • Listeria monocytogenes
  • N. meningitidis
  • CMV
  • JC virus
  • Cryptococcus neoformans
  • Toxoplasma gondi (brain abscess)
  • Enteroviruses (coxsackievirus, poliovirus, echovirus)
  • HSV-1
  • HSV-2
  • Naegleria fowleri
  • Cryptococcus neoformans
  • West Nile Virus
  • LCMV
  • Definitions
    • meningitis
      • inflammation of the meninges
      • bacterial meningitis can be life-threatening
      • remember: encephalitis is inflammation of the brain parenchyma
    • aseptic meningitis ("sterile meningitis")
      • meningitis caused by organisms other than bacteria
      • majoriy due to viruses
        • enteroviruses are the most common viral cause
  • Clinical presentation
    • fever, headache, altered mental status, neck stiffness
      • there may be variations in clinical presentation
        • due to the type of pathogen, patient age, host immune status
  • Bacterial causes of meningitis by age
    • < 1 month
      • Group B streptococcus (GBS), E. coliL. monocytogenes
        • prominent causes of meningitis in neonates
        • GBS and E. coli are most common
    • ≥ 3 month - < 10 years
      • S. pneumoniae and N. meningitidis are common
      • H. influenze type B
        • incidence decrease since HiB vaccine introduction in 1980s
    • ≥ 10 years - 34 years
      • S. pneumoniae and N. meningitidis are common
    • 18 years - 34 years
      • S. pneumoniae and N. meningitidis are common
    • > 35 years
      • S. pneumoniae is common
  • Meningitis in Immunocompromised (IC)
    • S. pneumoniae and L. monocytogenes are common
  • Aseptic meningitis
    • more common than bacterial
    • can occur at all ages
      • more common in children
        • summer months
  • Herpes simplex virus (HSV)
    • HSV-1
      • more associated with encephalitis
    • HSV-2
      • more associated with meningitis
  • See also "Meningitis"
  • Treatment
    • drug choice depends on what is the most likely pathogen causing meningitis
      • 0 - 28 day old
        • IV ampicillin + cefotaxime or an aminoglycoside (i.e., gentamicin, tobramycin)
      • ≥ 1 month old
        • IV vancomycin + cefotaxime or ceftriaxone
        • if you suspect L. monocytogenes, add ampicillin
      • adults
        • IV vancomycin + cefotaxime or ceftriaxone
        • If > 50 years old, add ampicillin
  • Abbreviations
    • IC = immunocompromised
    • AC = aseptic causes
    • blue = common pathogen in chart


 

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