systemic microbiology

1. CENTRAL NERVOUS SYSTEM
MENINGITIS
•
•Dr. Mahadi H Abdallah

2. CNS infection:
The CNS can be infected by
bacteria, viruses, fungi and protozoa.
Meningitis: infection of meninges
(membranes that cover the brain and
spinal cord).
Encephalitis: infection of brain
matter.
Meningoencephalitis: infection of
both brain and meninges.
Brain abscess: local lesion of brain.

3. ROUTE OF INFECTION
1. Haematogenous:
The meninges infected via respiratory tract
through the blood stream.
2. Direct
From Otitis media, sinusitis (Pneumococci &
Haemophilus) ,(through the nose).
3. Trauma:
• Neurosurgery (predisposing factor).
• Spinal anesthesia.

4. CLINICAL FEATURES
• headache
• irritability or drowsiness, sometimes with alteration of
consciousness
• fever
• neck stiffness
• photophobia
• Positive Kernig's sign (pain in the lumbar region on
straight-leg raising

5. • Most infections are acute and the commonest pathogens
are viruses, especially in children and young adults.
• Bacterial meningitis (pyogenic).
• Viral meningitis aseptic or lymphocytic

6. MENINGITIS
Bacterial meningitis:
Aetiological agents:
It is mainly caused by N. meningitides -S.pneumoniae
- H. influenzae.
And then by L.monocytogenes -
Pseudomonas, S.aureus coagulase -ve staph
Chronic meningitis
Mycobacterium tuberculosis - Actinomyces - Brucella
- Salmonella - Leptospira - T.pallidum.

7. •Neisseria menigitidis:
• cause epidemic meningitis. The important
serotypes A, B, C, Y, and W 135.
•H. Influenzae:
cause meningitis in infants and preschool
age 1month to 4 years between.

8. MENINGITIS
• Streptococcus pneumoniae
• Affect middle age group and elderly, espicially the
patients who are poor in health.
• L. monocytogenes: Elderly patients, pregnant female
and immunosuppressed patients.
• M. tuberculosis:
• affect all age group (children) Haematogenous spread of
the organism through the blood

9. NEONATAL MENINGITIS
• may be classified as early- ( within 7 days of birth) or
late-onset disease(occurring between 1 week and 3
months).
• Early infections are acquired from the mother, whereas
late infections may result from cross-infection after birth.
• The commonest causes of early-onset disease are
Group B (-haemolytic streptococci)
• coliforms such as Escherichia coli.
• Listeria monocytogenes is less common

10. MENINGITIS
• The majority of cases of bacterial meningitis occur in
childhood.
• The commonest cause is now Neisseria meningitidis
(serotype A, B and C).
• Haemophilus influenzae.
• In later life, pneumococci are more likely pathogens.

11. • Listeria monocytogenes is a relatively rare cause
• but should be considered particularly in pregnant and
immunocompromised patients.

12. VIRAL MENINGITIS
It is more common, benign and self
limiting disease.
The most important group of viruses is:
Enteroviruses (coxsackie) - Mumps -
herps simplex , Echoviruses
,Arbovirus.

13. FUNGAL MENINGITIS
Mainly in immunosuppressed patient:
1. Cryptococcus neoformans (capsulated
yeast).
2. Coccidiodes immites (in South
America).
3. Aspirogellus species.
4. Candida.

14. LAB DIAGNOSIS
Specimens:
C.S.F, Blood.
Collection:
C.S.F is collected by experienced health worker,
under aseptic condition(4th & 5th lumber
vertebrate)
Macroscopical examination
Clear - purulent - cloudy - Xanthochromic (red-
yellow, indication to haemorrhage) - clots &
deposit (large number of WBCs).

15. LAB DIAGNOSIS
Cell count:
• Normal count 5 cell/ml.
Centrifugation:
• For culture & staining (if C.S.F clear).

17. LAB DIAGNOSIS
Culture:
• Blood Agar + Chocolate BA (incubation in CO2).
• Add MacConkey if the specimen from neonate.
• L J media: Tuberculous meningitis.
• Saborand's media: fungal meningitis

18. LAB DIAGNOSIS
Direct examination (staining):
• Gram stain: is very important because it help in the
selection of drugs.
• Capsule stain: for fungi (Cryptococcus neoformans).
• Fluorchrome stain: acridine orange.
• Z.N stain.
• Quellung test for detection of capsular Ag.

19. LAB DIAGNOSIS
Ag detection:
• Latex agglutination test.
• ELISA
VDRL for diagnosis of syphilis.

20. CNS INFECTIONS
• Infections occur in the brain (encephalitis and brain
abscess),
• spinal cord (myelitis),
• Nerves (neuritis or polyneuritis.
• nervous tissue has poor repair mechanisms, and tissue
damage leads to long-term sequelae.

21. • Encephalitis is predominantly a viral disease(HSV).
• brain abscesses are predominantly bacterial in origin
and arise because of spread from other sites such as
infected cardiac valves and bones, mastoid sinuses and
chronic middle ear infection

22. • S. aureus, streptococci,
• Gram-negative bacilli, anaerobes and are often mixed..
• Multiple abscesses/cysts may be due to either bacteria
or Echinococcus granulosus (termed hydatid disease),
• Toxocara spp. (toxocariasis) or tapeworm infection
(which are zoonoses