Microbial Disease of Central Nervous System

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•     MICROBIAL DISEASES OF NERVOUS SYSTEM


•     ROUTES OF INFECTION
•     Organisms may gain access to CNS by several primary routes:
1.Hematogenous spread:
   - most common
   - entry into the subarachnoid space through the choroid plexus or via other blood vessels of brain
2.Inhalation of aerosolized respiratory droplets.
  

•     Contd….
3.Direct spread from an infected site:
   - The extension of infection close to CNS can occasionally occur.e.g.include otitis media, sinusitis
4.Anatomic defects in CNS structures:
  - As a result of surgery, trauma or congenital abnormalities can allow microorganisms easy and ready to access to CNS
5.Travel along nerves leading to brain:
 - Least common route of CNS infection caused by organisms such as rabies virus, herpes simplex virus, which travel along peripheral sensory nerves.
5.Through faeco-oral route.e.g.polio virus
7.Contamination of wound by spore bearing bacilli.e.g Clostridium tetani.
8.Ingestion of preformed toxin in food.e.g.Clostridium botulinum.
•     DISEASES OF NERVOUS SYSTEM
•     Meningitis:
  - Caused by bacteria,viruses,fungus & parasites.
  - Infection within the subarachnoid space or throughout the leptomeninges is called meningitis.
  - Based on host’s response to the invading microorganisms, meningitis is divided into two major categories:
        1.Purulent meningitis(bacterial meningitis)
        2.Aseptic meningitis(viral meningitis)
•     BACTERIAL MENINGITIS
•     Much more serious than viral.
•     Can cause severe disease resulting in brain damage and death.
•     The  major causes:
    - Hemophilus influenzae
    - Neisseria meningitidis
    - Streptococcus pneumoniae
    - Streptococcus agalactiae
Others :
    - Staphylococcus aureus
    - Escherichia coli
    - Listeria monocytogens
   
•     COMMON CAUSE OF MENINGITIS
•     Organism
•     Age group
•     Streptococcus agalactiae
•     Neonate to 3 month of age
•     Escherichia coli
•     Neonates
•     Listeria monocytogenes
•     Neonates,elderly,immunocompromised children and adults
•     Hemophilus influenzae
•     Children 6 months to 5 years
•     Neisseria meningitidis
•     Infants to 5 years and young adults
•     Streptococcus pneumoniae
•     All age groups,highest incidence in elderly
•     Cryptococcus neoformans
•     AIDS patients
•      
•     CONTD…..
•     Purulent meningitis:
  - Marked, acute inflammatory exudates with large no. of polymorphonuclear cells
  - Frequently, the underlying CNS tissue may be involved.
  - Meningitis can be either acute or chronic
 1.Acute meningitis: characterised by fever,stiff neck,headache,nausea,vomiting,neurologic abnormalities and change in mental status.
•     Contd…
2.Chronic meningitis:
-Often occurs in patients who are immunocompromised.
-Characterized by fever,headache,stiff nneck,nausea,vomiting,lethargy,confusion,mental deterioration.
- CSF findings- elevated protein and decrease glucose content.
•     VIRAL MENINGITIS
•     Causative agents:
-  Enterovirus
-  Adenovirus
-        Arbovirus
-        Herpes simplex virus
-        Cytomegalovirus
-        Japanese encephalitis virus
-  Epstein-Barr virus
•     Contd….
•     Aseptic meningitis:
-  Commonly associated with viral infections
-        Characterized by increase of lymphocytes and other mononuclear cells in the CSF and negative bacterial and fungal culture.
-        Patients may have fever,headache,stiff neck,nausea and vomiting.
•     Contd…
•     Encephalitis/Meningoencephalitis:
-  Usually a result of viral infection
-        Encephalitis is an inflammation of the brain parenchyma.
-        Concomitant meningitis that occurs with encephalitis is known as meningoencephalitis.
•     FUNGAL MENINGITIS
•     Causative agents:
- Cryptococcus neoformans
- Coccidoides immitis
- Histoplasma capsulatum
•     Transmitted by the respiratory route; spreads through blood to the CNS
•     Mortality up to 30% – Primarily affects AIDS patients.
•     PARASITIC MENINGITIS
•     Causative agents:
-Nagleria fowleri
-Toxoplasma gondii
-Trepanosoma brucei
•     OTHER DISEASES OF NERVOUS SYSTEM
  Disease                                Causative agent
Poliomyelitis                 Polio virus
Rabies                            Rabies virus
Tetanus                          Clostridium tetani
Botulism(food poisoning) Clostridium botulinum
Leprosy                         Mycobacterium leprae
•     PRION DISEASES
-        Transmitted by ingestion or inherited.
-        Very slow progressive disease that may attack proteins in CNS
-        Proteinaceous infectious particle- composed of protein designted as the scrapie isoform of the prion protein,PrPsc.
-        Prions convert normal proteins into abnormal proteins
-        Damage to brain gives brain tissue a spongy appearance –         encephalopathy
-  e.g.kuru,Creutzfeldt-Jacob disease,bovine spongiform encephalopathy.

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