Bacterial meningitis pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aysha Anwar, M.B.B.S[2]

Pathophysiology

Pathogenensis of bacterial meningitis is a complex process which may occur due to imbalance between the host immune response and virulence factors of pathogen causing infection. Following steps may explain the underlying process in a comprehensive way:

Transmission

• H. influenza type b and N. meningitides may be transmitted by close contact or prolong contact with patient suffering from meningitis
• It may also spread by exchanging throat and respiratory secretions (couging and kissing)
• Listeria monocytogenes may spread by eating contaminated food.
• Most people are carriers and do not develop the disease.

Colonization and evasion of host immune response

• Colonization of pathogenic organism involves evasion of host immune response mechanism.
• IgA protease produced by bacterial pathogen cleave mucosal IgA antibodies which prevent the bacteria from attachment to the mucosal surface.
• Once host immune response is evaded, bacteria attach themselves to the mucosa via fimbriae or pilli which facilitate colonization process.

Invasion and seeding

• Once colonized, the invasion of bacteria occurs via special adhesion proteins called adhesins.
• Adhesins may help bacteria to cross epithelial barrier intracellularly or intercellularly.
• Bacteria seeds transcellularly to enter the intravascular space.
• Surface encapsulation may play important role in entry of bacterial pathogen across epithelium into blood stream
• Blood stream entry of bacterial pathogen may result in activation of complement pathway and infalmmatory process
• Bacterial capsule helps evasion of complement system and ultimate entry into the CNS through blood brain barrier
• Individual genetic susceptibilty and immune response determine the severity of infection

Meningeal infalmmation

• Meningeal inflammation follows bacterial invasion into the blood.
• Bacterial entry into brain may occur through highly vascularised areas such as leptomeningeal blood vessels or choroid plexus.
• Intracranial entry of bactrial pathogen through tight junctions of blood CSF or blood CNS barrier mayroid epitheo occur through special interaction of adhesins and proteins on the surface of choroid epithelial cells

Associated conditons

Following conditions may increase the susceptibitly to develop bacterial meningitis:

• Trauma to skull
• HIV
• Diabetes mellitus
• Organ transplant

References

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