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MNI (immuno path) > L36- Nervous System and Special Senses Infections I > Flashcards

L36- Nervous System and Special Senses Infections I Flashcards

1
Q

list the common pathways of microbes for CNS infections

-also list the infrequent pathways

A
  • blood / hematogenous
  • peripheral nerves
  • adjacent bone, adjacent sinus
  • anatomical defects: congenital, surgical, traumatic

Infrequently: BBB, BCSFB (blood-CSF barrier)

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2
Q

define the following:

  • (1) meningitis
  • (2) encephalitis
  • (3) meningoencephalitis
  • (4) ependymitis
  • (5) choroid plexitis
A

1- inflammation of meninges (brain, spinal cord)
2- inflammation of brain parenchyma
3- inflammation of meninges and brain parenchyma

4- inflammation of ventricular walls
5- inflammation affecting choroid plexus

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3
Q

define the following:

  • (1) empyemas
  • (2) cerebritis
  • (3) myelitis
A

1- subdural empyema, caused by infection + collection of focal purulent material in space between dura and arachnoid

2- inflammation of cerebrum ==> abscess

3- inflammation of spinal cord

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4
Q

define the following:

  • (1) ADEs

- (2) spongiform encephalopathies

A

1- acute disseminated encephalomyelitis: post-encephalitis with attack to myelin

2- prion diseases OR transmissible spongiform encephalopathies (TSEs) = family of rare progressive neurodegenerative disorders (affects humans and animals)

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5
Q

list the common examples of septic meningitis

A
  • **Strep. pneumoniae
  • N. meningitidis
  • H. influenzae
  • S. aureus
  • CoN Staph. (coagulase neg.)
  • Gram neg. bacilli
  • listeria monocytogenes
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6
Q

list the common examples of aseptic meningitis

A

Tb

Non-Tb:

  • spirochetes (bacteria)
  • cryptococcus (fungal)
  • enteroviruses, arboviruses (viral)
  • toxoplasma gondii (parasite)
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7
Q

describe the timeline classification of meningitis (acute, subacute, chronic)

A

Acute <24hrs
Subacute <7 days
Chronic >4wks

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8
Q

describe the general timeline for meningitis based on etiology / infections type- order from rapid to slow onset

A

Acute:

  • Virus: hrs - 1day
  • Aerobic Bacteria: hrs - few days

Chronic:

  • Anaerobic Bacteria, Tb, Fungi: days - wks
  • Parasites, Syphilis: wks - yrs
  • Prions: yrs
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9
Q

Meningitis:

  • mostly seen in (1) age group
  • (2) are the hallmark Sxs
  • (3) are the many other possible Sxs
  • (4) is unique to meningococcal infections
A

1- children, elderly

2- fever (sudden rise), neck stiffness / nuchal rigidity (often not in children), heavy HA

3:

  • n/v
  • seizures (minimal), painful photophobia / phonophobia
  • loss of concentration / confusion (minimal)
  • sleepiness / difficult awakening
  • lack of appetite, insatiable thirst

4- rashes: flat, purple, constant

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10
Q

Meningitis:

  • (1) Triad of Sxs, seen in (2)% of pts
  • (3) describe the physical exam signs
A

1- HA, fever, neck stiffness (often not in children)
2- 85% pts

3:

  • Nuchal Rigidity: resistant passive flexion
  • Kernig’s Extension: slow extension of knee with thigh flexed –> pain, neck flexion
  • Brudzinsky’s sign: flexion of neck causes hip flexion
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11
Q

Meningitis Tests:
______ = flexion of neck causes hip flexion

______ = slow extension of knee with thigh flexed illicits pain and neck flexion

A

1- Brudzinsky’s sign

2- Kernig’s Extension

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12
Q

Meningitis Diagnosis:
-Imaging is always performed in patients presenting with the following, (1), before (2) is performed

  • (3) are the initial studies
  • (4) are additional CSF studies
  • (5) are the pathogen specific studies
A

1- dec consciousness, seizures, immuno-compromised, focal neurological deficits (want to avoid herniations)
2- Lumbar Puncture

3- CSF: opening pressure (LP => ICP), glucose content, protein content, cell count, Gram stain and culture (note HSV PCR is often tested since #1 cause)

4- CSF: serology for arboviruses (no PCR); note peak viremia occurs before onset of Sxs

5- pathogen specific PCR

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13
Q

list the causes of bacterial meningitis (septic) by age group

A

Neonates: *group B Strep., E. coli K1, Strep. pneumoniae, Listeria monocytogenes (vertical transmission)

Infants / Children: S. pneumoniae, N. meningitidis, H. influenzae type B (Hib), group B Strep.

Teens / Young adults: N. meningitidis, S. pneumoniae

Older adults: S. pneumoniae, N. meningitidis, Hib, group B Strep.. L. monocytogenes

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14
Q

list the bacterial causes of septic meningitis that have vaccines

A
  • N. meningitidis (type A, C – not B)
  • H. influenzae type B (Hib) — <1y/o
  • Strep. pneumoniae — pneumovax 23 (older adults or susceptible individuals)

Note- vaccine based on capsule

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15
Q

describe the important shared virulence factors for meningitis among the following:

  • N. meningitidis
  • H. influenzae
  • S. pneumoniae
A
  • N. menigitidis: capsule, IgA protease, pili, endotoxin (LOS)
  • H. influenzae: capsule, IgA protease, pili, endotoxin (LOS)
  • S. pneumoniae: capsule, IgA protease
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16
Q

LPs are taken from the ______ intervertebral spaces

A

Adults: between L3/L4, L4/L5

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17
Q

CSF findings for bacterial meningitis (indicate elevated, normal, depressed where indicated):

  • (1) appearance
  • (2) opening pressure
  • (3) WBC count (and type)
  • (4) protein
  • (5) glucose
A 
1- cloudy
2- elevated
3- elevated, >80% PMNs
4- elevated
5- depressed
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18
Q

CSF findings for viral meningitis (indicate elevated, normal, depressed where indicated):

  • (1) appearance
  • (2) opening pressure
  • (3) WBC count (and type)
  • (4) protein
  • (5) glucose
A 
1- clear
2- n/a
3- elevated, >50% lymphocytes, <20% PMNs
4- elevated
5- slightly depressed to normal
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19
Q

CSF findings for fungal meningitis (indicate elevated, normal, depressed where indicated):

  • (1) appearance
  • (2) opening pressure
  • (3) WBC count (and type)
  • (4) protein
  • (5) glucose
A 
1- cloudy
2- elevated
3- elevated, >50% lymphocytes
4- elevated
5- slightly depressed to normal
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20
Q

CSF findings for Tb meningitis (indicate elevated, normal, depressed where indicated):

  • (1) appearance
  • (2) opening pressure
  • (3) WBC count (and type)
  • (4) protein
  • (5) glucose
A 
1- fibrin-web
2- n/a
3- elevated, >80% lymphocytes
4- elevated
5- depressed
21
Q

list the Ags tested for in CSF screening (note- not ordered routinely, explain)

A

Bacteria: S. pneumoiae, N. meningitidis, H. influenzae type B (Hib)

Fungal: cryptococcus neoformans

Note- low specificity, low sensitivity

22
Q

list the indications where imaging (CT/MRI) should be performed before Lumbar Puncture

A
  • *papilledema
  • *abnormal level of consciousness
  • *immunocompromised state
  • h/o CNS disease (mass lesion, stroke, focal infection)
  • seizure w/in wk of presentation
  • focal neurological deficits (dilated non-reactive pupil, gaze palsy, arm/leg drift)
23
Q

list the complications of bacterial meningitis (septic)

A
  • seizures
  • loss of hearing or vision
  • irreversible brain damage
  • hydrocephalus
  • subdural effusion

-septic shock – DIC

24
Q

describe the highlight microbial features of N. meningitidis (gram stain, shape)

list relevant serotypes

A

(Neisseriaceae family)
Gram-, facultative intracellular diplococci

A (Africa), B (kids, not in vaccine), C, X, Y, Z, W135, L

25
Q

N. meningitidis culturing:

  • (1) sample sites
  • (2) describe agar(s)
  • (3) may used in co-agglutination systems for early identification
  • (4) may also be performed on (1) samples
A

1- blood, CSF — must process quickly

2: (fastidious organism- must grow in blood)
- (from sterile sites) Chocolate agar (Hemin / factor X, NAD / factor V) at 37C, 3-10% CO2
- Thayer-Martin (selective media)

3- Anti-capsular antisera
4- PCR

26
Q

N. meningitidis compared to N. gonnorrhea based on the following lab tests:

  • oxidase
  • glucose
  • maltose
  • sucrose
A

N. meningitidis: oxidase+, glucose+, *maltose+, sucrose-

N. gonnorrhea: oxidase+, glucose+, *maltose-, sucrose-

note- for sugars, yellow is positive and red is negative

27
Q

name the associated N. meningitidis virulence factors:

  • (1) allows for colonization and invasion of nasopharynx
  • (2) anti-phagocytic function
  • (3) endotoxin
  • (4) anti-complement (C3)
A

1- IgA protease (to cross mucosa)
2- capsular polysaccharide
3- Lipo-oligosaccharide, released in blebs
4- Factor H binding protein

28
Q

name the associated N. meningitidis virulence factors:

  • (1) outer membrane protein facilitating attachment
  • (2) outer membrane protein facilitating invasion
  • (3) outer membrane protein facilitating colonization and invasion
A

1- Opacity proteins (Opa, Opc)
2- PorA, PorB- produces pores
3- type IV pili/fimbria- also phase and antigenic variation

29
Q

list the important virulence factors for N. meningitidis

A
  • type IV pili (colonization, invasion)
  • opacity proteins: Opa, Opc (attachment)
  • PorA, PorB (invasion)
  • lipo-oligosaccharide (endotoxin)
  • capsular polysaccharide (anti-phagocytic)
  • Factor H binding protein (anti-complement, C3)
  • IgA protease (colonization, invasion – cross mucosa)
30
Q

briefly compare BBB to BCSFB

A

BBB: endothelium with tight junctions –> perivascular space –> astrocytic feet (glial limitans)

BCSFB: normal endothelium –> stroma –> epitheium with tight junctions

31
Q

list the main CA causes of bacterial meningitis, include:

  • site of entry
  • age range
  • predisposing conditions
A

N. meningitidis:

  • nasopharynx
  • all ages
  • none predisposition, close quarters (dorms, daycare) is risk

Strep. pneumoniae:

  • nasopharynx – extension of skull fracture, distant foci
  • all ages
  • any and all conditions that predispose pneumococcal bacteremia
32
Q

list the main HA causes of bacterial meningitis, include:

  • site of entry
  • age range
  • predisposing conditions
A

S. aureus:

  • bacteremia, foreign body, skin
  • all ages
  • endocarditis, surgery, foreign body

Gram- bacilli:

  • various entries
  • older adults and neonates
  • advanced illness, neurosurgery
33
Q

list the other common causes of bacterial meningitis that are not CA or HA associated (hint- 3), include:

  • site of entry
  • age range
  • predisposing conditions
A

Listeria monocytogenes:

  • GIT, placenta
  • older adults, neonates
  • defects in cell-mediated immunity

Group B Strep. (agalactiae):

  • nasopharynx
  • older adults, neonates
  • post-partum

H. influenzae:

  • nasopharynx
  • adults (unvaccinated infants, children)
  • diminished humoral immunity
34
Q

list the main risk factors for N. meningitidis

A
  • nasopharynx carriers — 10-20% of population
  • close quarters (military, dorms)

-**Early (C3/properdin) and Late components of complement system

35
Q

N. meningitidis:

  • (1) transmission
  • (2) age group predominance
  • (3) season predominance
A

1- droplets, direct contact

2- children, teenagers

3- winter (Feb - Mar)

36
Q

N. meningitidis:

  • (1) USA serogroups
  • (2) serogroup is associated with large-scale epidemics
A

1- B (children), C, Y

2- A (Africa)

37
Q

N. meningitidis:

  • vaccine is based on (1) serogroups, compare both types
  • (2) is the other vaccine
A

1- A, C, W135, Y

  • conjugated <55 y/o
  • polysaccharide >2y/o

2- B capsule: similar to ICAM adhesion molecule — vaccine in some other countries

38
Q

N. meningitidis clinical presentation:

  • (1) common Sxs
  • (2) common complication
  • (3) describe frequency of neurological Sxs
A

1- low BP, elevated pulse rate, diaphoresis + petechiae and ecchymoses

2- shock via DIC

3- seizures and other Sxs are less common than in other meningitis

39
Q

H. influenzae:

  • (1) classic microbial features
  • colonizes (2) usually
  • (3) is the major virulence factor and serotype
A

1- Gram- rod, oxidase+

2- respiratory tract

3- capsule (strains a-f) — type b is most invasive (polyribose phosphate capsule – Hib)

40
Q

list the many H. influenzae meningitis risk factors

A
  • *URI
  • *daycare
  • H. influenzae Otitis media
  • sinusitis, pharyngitis
  • cancer
  • pregnancy
  • older age
  • weakened immune system
41
Q

what is the goal of H. influenzae vaccine

A

give as early as possible to prevent colonization in nasopharynx

42
Q

GBS = (1):

  • (2) classic microbial features
  • commonly colonizes (3), therefore (4) are at high risk for infection
A

1- group B Strep., S. agalactiae

2- Gram+ cocci, β-hemolytic, bacitracin resistant

3- genital (10-30% women), GIT, URT (infants)
4- transferred during vaginal delivery

43
Q

Strep. agalactiae meningitis:

  • (1) serotypes
  • (2) onset of infection / incubation
  • (3) fatality rate
A

1- Ia, Ib, II, *III (most virulent, most common cause in neonates), V

2- early w/in 7 days OR late 7 days - 3 mos

3- 5-15%

44
Q

Strep. pneumoniae meningitis:

  • (1) classic microbial features
  • (2) describe prevalence
  • (3) vaccines
A

1- Gram+, α-hemolytic, diplococci-lancet shape, optochin sensitive

2- most common bacterial etiology of meningitis in adults of all ages and children >1mo

3- Prevnar 13 (<2y/o), Pneumovax 23 (<2y/o)

45
Q

Listeria monocytogenes meningitis:

  • (1) classic microbial features
  • (2) association in terms of transmission
  • (3) season prevalence
A

1- small Gram+ bacilli, tumbling motility, facultative anaerobe, β-hemolytic, grows at low T

2- food, placenta

3- summer months

46
Q

list the virulence factors of Listeria monocytogenes

A
  • Internalin (InlA, InlB): adheres to cadherin in intestinal wall, allows invasion
  • Lysteriolysin O (LLO): to escape endosome into cytosol
  • Actin A motility (ActA): actin polymerization allows cell-to-cell transmission
47
Q

Listeria monocytogenes cause what syndromes in the following populations:

  • (1) healthy average adult
  • (2) pregnant women
  • (3) elderly person
A

1- cold Sxs

2- placenta invasion –> miscarriage

3- brain invasion –> death

48
Q

Listeria monocytogenes diagnosis:

  • (1) samples for culture
  • (2) hallmark result in LP
  • (3) is recommended in all pts with Listeria meningitis
A

1- CSF, blood

2- CSF with substantial Lymphocyte (>25%) elevation – not PMNs

3- MRI with contrast due to inc ICP

49
Q

E. coli K1:

  • (1) classic microbial features
  • produces (2)
  • (3) transmission
A

1- Gram- bacilli

2- siderophore production (Fe sequesteration), endotoxin production

3- food, water, person-person

MNI (immuno path) (14 decks)

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