Ch. 23 Disease Of The Cns

Front 1

Barriers to CNS infections

Back 1

1. Anatomical- Bones and membranes protect CNS from external environment. Bones and membranes create limited space – effects of infections magnified
2. Physiological- Blood-brain barrier prevents entry of microbes and toxic substances into CSF. Blood-brain barrier prevents passage of antibodies, cytotoxic cells and antimicrobial drugs into CNS

Front 2

Classification of CNS infections

Back 2

1. Encephalitis – infection of brain parenchyma
2. Meningitis – infection of meninges
3. Myelitis – infection of spinal cord tissue
4. Neuritis – infection of peripheral nerves

Front 3

Microbial entry to CNS

Back 3

1. Microbes usually start in peripheral tissues then move to CNS hematogenously- Nasopharynx, GI tract
2. Enter via direct inoculation – trauma
3. Enter via neural pathways- HSV, rabies
4. Some viruses remain sequestered in CNS in a latent state- HSV, varicella-zoster

Front 4

Defenses in CNS

Back 4

1. Antibodies uncommon- Complement levels low
2. Specialized phagocytes – microglia- Phagocytosis hampered by low levels of complement and antibodies to opsonize microorganisms

Front 5

Tissue damage in CNS infections is caused by?

Back 5

Bacterial toxins, Viral lytic cycles, Intracellular growth of bacteria and fungi,Most damage from host’s inflammatory response

Front 6

Host response to CNS infection

Back 6

1. Viruses and intracellular bacteria – “aseptic meningitis”
Increase in lymphocytes and monocytes
Slight increase in protein levels
Glucose levels constant
2. Extracellular bacteria – “septic meningitis”
Increased levels of neutrophils
Protein levels increase significantly
Glucose levels decrease

Front 7

Enterovirus (picornavirus family)- Polio virus infection

Back 7

1. Nonenveloped
2. ssRNA(+) sense genome
3. Nonsegmented genome-Encodes polyprotein – cleaved into enzymes and structural proteins and Protease degrades cap-binding protein of host mRNA
4. 5’-untranslated leader sequence on RNA

Front 8

Salk polio vaccine (IPV)

Back 8

1. Introduced 4-12-55- Killed virus vaccine- Contains serotypes 1, 2, and 3
2. Injected; boosters required- Elicits only IgG and IgM
3. Currently used in U.S.

Front 9

Sabin polio vaccine (OPV)

Back 9

1. Attenuated live vaccine given orally-Contains serotypes 1, 2, and 3
2. Replicates well in GI tract but not in neural tissue- Elicits synthesis of IgA
3. May occasionally revert
4. Not used in U.S.

Front 10

Bacterial meningitis

Back 10

Bacteria colonize and invade mucosa

Front 11

Bacterial meningitis virulence factors

Back 11

1. IgA proteases, Prevention of ciliary action and Attachment structures that include: Adhesins, Pili and Capsules
2. Mechanisms for crossing mucosa to bloodstream: Endocytosis and Damage to tight junctions
3. Capsules provide protection in bloodstream

Front 12

How does Bacterial meningitis cross the BBB

Back 12

1. Bacteria attach to blood vessels
2. Damage to endothelial cells causes inflammation
3. Endothelial lining of vessels becomes “leaky”
4. Some species travel in monocytes

Front 13

Neonatal meningitis- what are the 2 main causes?

Back 13

Group B streptococci and E. coli K-1

Front 14

Group B streptococci- Neonatal meningitis

Back 14

1. Main cause of neonatal meningitis- Gram(+) cocci
2. 5 different capsular serotypes
3. No vaccine

Front 15

E. coli K-10- cause of neonatal meningitis

Back 15

1. Second most common cause- Part of resident biota
2. Gram (-) rods
3. Capsule – sialic acid: Serum resistance and Antiphagocytic
4. No vaccine

Front 16

Streptococcus pneumoniae

Back 16

1. Common cause of meningitis in adults. Moves from lungs or sinuses to bloodstream
2. Polysaccharide capsule- Used for 2 vaccines

Front 17

Haemophilus influenzae type b

Back 17

1. Previously most common cause of meningitis in children between 3 months and 5 years
2. Antiphagocytic polysaccharide capsule
3. Effective vaccine – conjugate vaccine

Front 18

Neisseria meningitidis

Back 18

1. Colonizes throat or nasopharynx - asymptomatic
2. Causes brain lesions

Front 19

Cryptococcus neoformans

Back 19

Causes brain lesions

Front 20

Diagnosis of meningitis

Back 20

1. CSF samples: Look for immune cells, Determine glucose level, Diagnostic kits for bacterial and fungal antigens
2. Blood samples are cultivated

Front 21

African sleeping sickness

Back 21

1. Caused by Trypanosoma brucei
2. Uniformly fatal within two years
3. Vaccine prospects poor due to antigenic variation
4. Drugs toxic, only effective in early stages
5. Carrier is the Tsete fly and trypomastigote is the is the infectious agent
6. Chronic disease: Causing Meningitis, Convulsions, Coma and Death
7. To control it must eliminate tsetse flies and block access of flies to humans in endemic areas