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Microbiology > Chapter 25 Central Nervous System Infections > Flashcards

Chapter 25 Central Nervous System Infections Flashcards

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Biology 101 flashcards
1
Q

How can pathogens traverse the blood-brain barrier?

A
  • growing across, infecting the cells that comprise the barrier
  • being passively transported across in intracellular vacuoles
  • being carried across by infected WBCs
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2
Q

What is meningitis?

A

inflammation of the membranes surrounding the brain

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3
Q

Which type of cells are mainly present in CSF in the case of septic (purulent) meningitis?

A

mainly neutrophils

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4
Q

Which type of cells are mainly present in CSF in the case of aseptic meningitis?

A

mainly mononuclear

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5
Q

How do CSF protein counts compare in septic versus aseptic meningitis?

A

septic: high (>100)
aseptic: moderately high (50-100)

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6
Q

How do CSF glucose levels compare in septic versus aseptic meningitis?

A

septic: <45 low
aseptic: normal

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7
Q

What causes meningococcal meningitis?

A

Neisseria meningitidis

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8
Q

What is the most common cause of bacterial meningitis?

A

Streptococcus pneumoniae

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9
Q

what are the important causative agents of non-viral meningitis?

A
  • Neisseria meningitidis
  • Haemophilus influenzae
  • Streptococcus pneumoniae
  • Escherichia coli
  • Listeria monocytogenes
  • Mycobacterium tuberculosis
  • Cryptococcus neoformans
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10
Q

What are the top three causative agents of bacterial meningitis?

A
  • Haemophilus influenzae type b (Hib)
  • Neisseria meningitidis
  • Streptococcus pneumoniae
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11
Q

Which virulence factors does Streptococcus pneumoniae have in common with N. meningitidis and H. influenzae, and which ones is it missing?

A

All three have a capsule and IgA protease, whereas Neisseria meningitidis and Haemophilus influenzae also have pili, endotoxin, and outer membrane proteins

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12
Q

Describe the quadrivalent vaccine for Neisseria meningitidis

A

targets A, C, Y, W serotypes of the polysaccharide capsule

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13
Q

Describe the bacterium that causes meningococcal meningitis

A

Neisseria meningitidis is a Gram-negative diplococcus. Uses pili to attach to epithelial cells in nasopharynx, carried asymptomatically by up to 20% of the population

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14
Q

What does a low CSF glucose level relative to serum glucose indicate and why?

A

bacterial infection, since bacteria use flucose feor metabolism

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15
Q

Which meningitis-causing bacteria are spread from person to person spread by droplet infection, and are frequently found in areas of overcrowding?

A

Neisseria meningitidis

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16
Q

In which groups does Streptococcus pneumoniae commonly cause bacterial meningitis?

A

children and the elderly

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17
Q

Describe Streptococcus pneumoniae

A

Gram-positive coccus, normal flora in throat, alpha-hemolytic

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18
Q

Why do babies not respond to PP23 meningococcal meningitis vaccine?

A

not conjugated

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19
Q

In what groups does Listeria monocytogenes cause meninigitis, and what are the symptoms?

A

in immunocompromised adults

-symptoms: about 4 days after flu like symptoms: fever, personality change, tremors, muscle contractions, seizures

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20
Q

What is/are the most frequent cause(s) of neonatal meningitis?

A

group B beta-hemolytic streptococci (GBS)

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21
Q

What is the histology of miliary tuberculosis?

A

lesions are millet seed-sized (1 mm diameter)

  • yellowish, firm areas without grossly visible caseation necrosis
  • structure of tubercles with minute areas of caseation necrosis
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22
Q

Describe the pathogenesis of Mycobacterium tuberculosis meningitis

A

Bacilli spread in CSF-> tuberculin reaction in meninges -> meningitis -> adhesions -> CSF pathways locked, nerves and blood vessels damaged

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23
Q

Which pathogen causes fungal meningitis?

A

Cryptococcus neoformans

24
Q

Which populations are at risk for fungal infections? What is the incubation period?

A

people with weakened immune systems; 2-11 months

25
Q

How is C. neoformans infection diagnosed?

A

antigen detection; antibody detection

26
Q

What is the treatment for cryptococcus? What is the mechanism of these medications?

A

IV amphotericin B (binds ergosterol and disrupts membrane permeability) and flucytosine (inhibits DNA synthesis) for 2-10 weeks, followed by oral fluconazole or itraconazole (inhibits sterol synthesis) for 6-12 months

27
Q

Which pathogen causes valley fever, what is the incubation period, and the symptoms?

A

-Coccidiodes immitis (Endemic to SW USA)
-1-3 week incubation period
-flu-like symptoms
fatigue, fever, cough, fever, shortness of breath, night sweats, muscle aches/joint pain, rash on upper body or legs, headache

28
Q

How can Valley Fever be diagnosed?

A

complement-fixing antibodies in the serum

29
Q

What is the difference between encephalitis and menigitis?

A

encephalitis is inflammation of the brain, whereas meningitis is inflammation of the lining of the brain/meninges.

30
Q

Name protozoa that enter via skin and/or respiratory tract and cause meningitis

A

Naegleria fowleri, Acanthamoeba spp., Balamuthia mandrillaris

31
Q

How does viral meningitis compare to bacterial meningitis?

A

milder, with headache, fever and photophobia, but less neck stiffness

32
Q

What symptoms would someone with encephalitis present with?

A

abnormal behavior, confusion, seizures, altered consciousness, N/V, fever

33
Q

Which virus causes severe and fatal encephalitis in a human bitten by an infected monkey?

A

B-virus

34
Q

Which virus was a common cause of encephalitis before vaccine was released, and had one of three serotypes that caused 75% of paralysis?

A

poliovirus

35
Q

Which pathogen cause an outbreak of hand-foot-mouth infection with a high rate of meningoencephalitis for children under age 5 and a 19% mortality rate

A

enterovirus 71

36
Q

describe the structure of poliovirus

A

positive sense ssRNA virus with icosahedral symmetry

37
Q

Describe the pathogen that causes rabies encephalitis

A

rhabdovirus is an enveloped, bullet-shaped ssRNA virus

38
Q

Which paramyxovirus causes encephalitis and is transmitted from pig to human and human to human?
How are pigs infected?

A 
Nipah virus
exposure to (eating food contaminated with) secretions of fruit bat and flying fox which carry the virus
39
Q

What causes changes in behavior in rabies encephalitis?

A

viral invasion of the limbic system

40
Q

What type of vaccine is given to prevent rabies?

A

active immunization with killed diploid cell-derived rabies virus

41
Q

Describe togaviruses

A

enveloped, +ve sense RNA viruses

42
Q

~30-45% of people with encephalitis caused by which virus will die from the disease?

A

Eastern equine encephalitis virus (EEEV)

43
Q

Which flavivirus infection is related to dengue, yellow fever, and West Nile virus?

A

Japanese encephalitis virus, transmitted by mosquitoes (pigs and birds and intermediate hosts), ~70K cases/yr in India and China, 30% mortality rate, vaccines available

44
Q

What is the inflammatory demyelinating condition of the PNS associated with a variety of infections, as well as with immunization with non-infectious material?

A

Guillain-Barre syndrome

45
Q

What neurological diseases have a possible viral etiology?

A
  • MS
  • ALS
  • Parkinson’s
  • schizophrenia
  • dementia
46
Q

What clinical presentation may children with severe CNS disease from parasites show?

A

ocular disease, hydrocephalus, convulsions, intracerebral calcifications

47
Q

How does Plasmodium falciparum cause cerebral malaria?

A

RBCs containing the asexual stages adhere to the walls of capillaries

48
Q

Why does Toxocara infection result in granuloma formation in brain and retina

A

humans are dead-end hosts

49
Q

What happens in the brain when humans ingest Echinococcus granulosus eggs?

A

embryos emerge and migrate through gut to blood vessels and develop into hydatid cysts in brain as well as in liver, lungs, kidney

50
Q

Which pathogen causes cysticercotic encephalopathy if the brain is heavily infected?

A

Taenia solium, the pork tapeworm

51
Q

Which pathogen crosses the blood brain barrier causing sleepiness, confusion, and behavioral changes? Does it have a vector?

A

Trypanosoma brucei gambiense

yes; tsetse fly

52
Q

How does Clostridium botulinum cause ‘floppy babies’?

A

toxin blocks acetylcholine release from peripheral nerves

53
Q

How does Clostridium tetani cause uncontrolled muscle spasms?

A

toxin tetanospasmin blocks releas of inhibitory mediators in spinal synapses

54
Q

How does the blood-brain barrier compare to the blood-CSF barrier?

A

The blood-brain barrier has thick basement membrane, no fenestrations in the endothelium, and the blood vessel is surrounded by astrocyte footplates (glial processes). Whereas the blood-CSF barrier has a thin basement membrane, fenestrated endothelium, and the blood vessel is surrounded by tightly joined choroid plexus epithelium

55
Q

Who is susceptible to Cryptococcus neoformans infections, what kind of pathogen causes the infection, what is the incubation period, and what symptoms are involved?

A

People with weakened immune systems are susceptible to this fungal infection with an incubation period of 2-11 months.
Symptoms if in lungs: cough, shortness of breath, chest pain, fever
Symptoms if in brain: headache, fever, neck pain, N/V, sensitivity to light, confusion or changes in behavior

56
Q

How can a Cryptococcus neoformans infection be diagnosed and treated (describe the mechanisms)?

A

Dx: Antigen detection and antibody detection
Tx: IV amphotericin B (binds ergosterol and disrupts permeability of membrane) and flucytosine (inhibits DNA synthesis) for 2-10 weeks.
Followed by oral fluconazole or itraconazole (inhibits sterol synthesis) for 6-12 months.

57
Q

Describe spongiform encephalopathies, including their causative agent.

A

Spongiform encephalopathies are caused by scrapie-type agents (prions). Appearance of spongiform appearance of nervous tissues, caused by vacuolation and plaque formation.

  • Infections in animals seem to have originated from sheep and goats with scrapie which has been present in Europe for 200-300 years.
  • Affected animals itch and scrape themselves against posts for relief

Microbiology (24 decks)

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