Meningeal defects and primitive ENT
infections are known to promote
pneumococcal meningitis. Other risk factors can be identified in the occurrence of community acquired
bacterial meningitis (CABM) and play a key role either in the frequency of this kind of
infection, the type of bacteria concerned, the prognosis or the risk of recurrence. Thus, epidural infiltrations are rarely responsible for staphylococcal or streptococcal
meningitis.
Cochlear implants are also known to increase the risk of
pneumococcal meningitis. The occurrence in children of
aseptic meningitis or
meningitis due to Staphylococcus aureus or Enterobacteriaceae is strongly suggestive of congenital spinal or cerebral anomalies (
dermal sinus or
spina bifida). MRI must be rapidly performed. In cases of
splenectomy or asplenism,
pneumococcal meningitis is common and must be prevented. According to the larger series available on this topic, age over 60,
diabetes mellitus,
alcoholism and immune deficiency are found to promote CABM in about 25% of cases. Streptococcus pneumoniae is the most frequent causative bacteria in elderly patients, in case of
alcoholism, as well as Listeria monocytogenes and some Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae). L. monocytogenes is frequently isolated in immunodepressed patients and patients treated by anti-TNF molecules (
infliximab notably). Finally, some genetic polyphormisms promote CABM:
complement and
properdin deficiencies (
meningococcal meningitis),
mannose-binding lectin deficiency, Fcgamma receptors alteration or
interleukin-1 and IL-1R polymorphisms. Screening for such
genetic disorders may be discussed in case of CABM but is mandatory in case of recurrent
meningococcal infections.