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Mechanisms of Microbial Disease > Chapter 16 > Flashcards

Chapter 16 Flashcards

1
Q

What must pathogens cross to cause encephalitis?

A

Frrom blood over the blood brain barrier

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2
Q

What must pathogens cross to cause meningitis?

A

From blood to the cerebrospinal fluid

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3
Q

How can microbes cross the BBB?

A

Growing across, infecting the cells that compromise the barrier
Being passively transported across in intracellular vacuoles
Being carried across by infected white blood cells
Moving through the interstitial space between cells

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4
Q

What are the cell, protein, glucose levels in a normal body?

A

0-5 cells/ml
15-45 mg protein/dL
45-85 mg glucose/dL

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5
Q

What are the cell, protein, glucose levels in septic meningitis (caused by bacteria)?

A 
200-20,000 cells/ml (mostly neutrophils)
High protein (>100) due to bacterial protein
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6
Q

What are the cell, protein, glucose levels in aseptic meningitis or meningoencephalitis?

A

100-1000 cells/ml (mainly mononuclear
Moderately high protein (50-100) because no bacteria
Normal glucose because viruses don’t metabolize

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7
Q

What causes bacterial meningitis (the more severe, less common meningitis)?

A

Neisseria meningitidis, streptococcus pneumonia, H. influenzae (before vaccination)

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8
Q

What are the virulence factors needed to cause bacterial meningitis?

A

Capsule (to prevent phagocytosis by blood complement system)
IgA protease
Pili, endotoxin and outer membrane proteins (N. meningitidis, H. influenzae) also help

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9
Q

Does gram positive or gram negative produce endotoxin?

A

Gram negative does

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10
Q

What pathogens cause bacterial meningitis in neonates (

A

Gram negative bacilli (E. coli, Klebsiella, Enterobacter)
Strep. agalactiae, Listeria monocytogenes
Has less well developed BBB

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11
Q

What pathogens cause bacterial meningitis in infants (

A

Strep. agalactiae, E.coli, H. influenzae, Strep. pneumoniae, N. meningitidis
Less well developed BBB

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12
Q

What pathogens cause bacterial meningitis in children and adults?

A

Strep. pneumoniae, neisseria meningitidis

Fully developed BBB

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13
Q

What pathogens cause bacterial meningitis in the elderly (>65 years)?

A

Strep. pneumoniae, N. meningitidis, Listeria monocytogenes, Aerobic gram negative bacilli
BBB starts disintegrating

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14
Q

How much of the population is a carrier for Neisseria meningitidis?

A

20% (higher rates seen in epidemics)

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15
Q

What causes meningococcal meningitis?

A

Neisseria meningitidis (looks like N. gonorrhea)

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16
Q

What are the virulence factors of Neisseria meningitidis?

A

Pili for attachment to the epithelium of the nasopharynx

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17
Q

How does neisseria meningitidis invade the blood and meninges?

A

Not well understood.
Individuals with C5-C9 complement deficiency are more susceptible.
Young children who have lost maternal antibodies and those who have never encountered the infecting serotype are at the greatest risk

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18
Q

What protects us from invasion of the blood and meninges?

A

Presence of antibodies to capsular antigens.

19
Q

How is neisseria meningitidis transmitted?

A

Droplets, overcrowding and confinement (prisons, dorms, military barracks)

20
Q

What is the peak time of year for neisseria meningitidis?

A

Winter/ early spring when carrier rates are 60-80%

21
Q

What is the clinical manifestation of meningococcal meningitis?

A

1-3 days after infection, sudden onset of headache, sore throat, drowsiness, stiff neck, hemorrhagic skin rash (indicates septicemia)
100% mortality untreated, 10% mortality if treated

22
Q

How can you prevent meningococcal meningitis?

A

Using a vaccine (routine childhood vaccination)
Polysaccharide for young children
Conjugate for >11 years

23
Q

How is meningococcal meningitidis diagnosed?

A

Essential to know whether it is viral or bacterial. Gram stain of CSF, culture and white cell counts

24
Q

What is haemophilus meningitis caused by?

A

Haemophilus infulenzae B (serotype based on capsule) fastidious
Resident of RT in infants and children and maternal antibodies protect the infant until 3-4 months when they wane
Window of susceptibility before developing its own antibodies

25
Q

What is the clinical manifestation of haemophilus meningitis?

A

5-6 days after infection hearing loss, delayed language development, mental retardation
Less fatal than meningococcal and pneumococcal

26
Q

How can we prevent haemophilus meningitis?

A

With the HiB vaccine after 2 months

27
Q

What causes pneumococcal meningitis?

A

Streptococcous pneumoniae
Encapsulated
Carried in the throats of many healthy people, rarely invades blood or meninges
Highest mortality rate

28
Q

What can make a person susceptible to pneumococcal meningitis?

A

Low levels of capsular antibodies, specific, >85 capsule types

29
Q

How can we prevent pneumococcal meningitis?

A

Heptavalent protein conjugate for 2-23 months and immunocompromised
23-valent for >5 years (could cause hypersensitivity reaction in babies)

30
Q

What typically causes viral meningitis?

A

Enteroviruses

31
Q

What is the clinical manifestation of viral meningitis?

A

Most common type, milder than bacterial (headache, fever, photophobia)
Complete recovery is typical

32
Q

How do you diagnose viral meningitis?

A

Difficult to isolate virus from CSF so diagnosis is done with viral genome detection (PCR)

33
Q

What is encephalitis?

A

Inflammation of the brain parenchyma, usually viral
Cerebral dysfunction is typical (abnormal behaviour, seizures, nausea, vomiting, fever)
HSV-2 most common cause

34
Q

How does HSV encephalitis clinically manifest in neonates?

A

Passage down the birth canal of a female shedding HSV-2

35
Q

How does HSV encephalitis clinically manifest in older children and adults?

A

HSV-1 viral reactivation in nerves in skull (trigeminal ganglia) and the infection spreading back to the temporal lobe of brain.
70% fatality if not treated

36
Q

How is HSV encephalitis treated?

A

Antiviral therapy for 21 days

37
Q

What are the symptoms of poliovirus encephalitis?

A

1-4 days of fever, sore throat, malaise
Effect of motor neurons is paralysis
Formerly the most common cause of encephalitis

38
Q

What is the only disease that has been eradicated from earth?

A

Smallpox, polio is likely to be next

39
Q

How can we prevent poliovirus encephalitis?

A

Using the inactivated vaccine or oral vaccine

40
Q

Who carries West Nile Virus?

A

Birds and culcine mosquitoes with humans and horses being incidental hosts
From Africa, Middle East spread to NYC 1999 by migrating birds

41
Q

How is West Nile Virus diagnosed?

A

RNA detection of West Nile Virus or IgM antibodies in sera/CSF

42
Q

How can we prevent West Nile virus?

A

No vaccine, only mosquito control

43
Q

What neurologic diseases may have a viral origin?

A

MS, Parkinsons, schizophrenia and senile dementia

44
Q

How did Alexander the Great die?

A

West Nile virus causing enephalitis

Mechanisms of Microbial Disease (17 decks)

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