PATHOGENS

• S. pneumoniae
• N. meningitidis
• Listeria monocytogenes
• Haemophilus influenzae
• Streptococcus agalactiae (Group B Streptococcus, GBS)
• Enterococcus (uncommon)
• For community-acquired bacterial meningitis, Streptococcus pneumoniae and Neisseria meningitidis usually account for 80% of all adult cases.
• The overall species-specific infection rates (all ages, 1997-2008 data[12]):
  • Streptococcus pneumoniae 58%
  • Group B streptococcus 18.1%
  • Neisseria meningitidis 13.9%
  • Haemophilus influenzae 6.7%
    • Note that the incidence of Haemophilus influenzae type b meningitis in children has been dramatically reduced with the introduction of the vaccine in 1986; most cases of H. influenzae meningitis are secondary to nonserotype b organisms or serotype b infections in non-vaccinated children and adults.
  • Listeria monocytogenes 3.4%
• Rates of community-acquired infection with specific pathogens are strongly influenced by age.
  • Children and young adults 2-29 yrs: N. meningitidis 60%, S. pneumoniae 27%, group B Streptococcus 5%, H. influenzae 5%, L. monocytogenes 2%
  • Adults 30-59 yrs: S. pneumoniae 61%, N. meningitidis 18%, H. influenzae 12%, L. monocytogenes 2%
  • Adults > 60 yrs: S. pneumoniae 61%, N. meningitidis 18%, H. influenzae 12%, L. monocytogenes 6%, Group B Streptococcus 3%