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M2 | Microbiolgy > Viral Exanthems > Flashcards

Viral Exanthems Flashcards

1
Q

Important properties of Varicella–Zoster virus

A
  • Large viruses
  • Icosahedral core surrounded by lipoprotein envelope
  • Linear double stranded DNA
  • No polymerase
  • Tegument
  • Replicate in nucleus
  • Form intranuclear inclusions
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2
Q

How VZV is transmitted ?

A
  1. Respiratory droplets

2. Direct contact with skin lesions

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3
Q

Explain pathogenesis of VZV

A

VZV infects mucosa of upper respiratory tract

  • VZV spreads via blood to skin, where papulovesicular rash appears in crops on trunk & spreads to head & extremities (Varecella).
  • Multinucleated giant cells with intranuclear inclusions are seen in base

of lesions.

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4
Q

VZV infects into cells of ……. neurons & carried by …….. axonal flow …………….ganglia (where VZV becomes latent).

A

Sensory neuron , retrograde axonal flow & dorsal root ganglia

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5
Q

Where is VZV DNA located in latency infected cell ?

A

Nucleus

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6
Q

What does each of varicella & zoster in VSV represents ?

A
  1. Varicella ——-> VZV spreads via blood to skin, where papulovesicular rash appears in crops on trunk & spreads to head & extremities
  2. Zoster ——-> painful vesicular lesions along course of sensory nerve of head or trunk
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7
Q

How zoster happens ?

A

Later in life, at times of reduced cell-mediated immunity or trauma, virus is activated ——-> zoster

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8
Q

Which Laboratory Diagnosis is done to identify VZV ?

A
  1. Tzanck smear ( Presumptive diagnosis)
    • isolation of virus in cell culture
    • identification with specific antiserum
      Both are definitive diagnosis
  3. Rise in antibody titer:
    diagnose of varicella
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9
Q

Important properties of Coxsackie Viruses

A
  • RNA Viruses
  • Picornavirus Family
  • Enteroviruses
  • Small nonenveloped
  • Icosahedral nucleocapsid
  • Positive Single-stranded RNA
  • No polymerase
  • replicate in cytoplasm of cells
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10
Q

Transmission of coxsackie viruses

A
  1. Fecal–oral

2. Respiratory aerosols

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11
Q

Classification of coxsackie

A
  1. Group A
  2. Group B
  3. Group A & B
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12
Q

Mention the diseases site associated with each group of coxsackie

A
  1. . Group A ———-> In skin & mucous membranes
  2. Group B ————> various organs such as heart, pleura, pancreas & liver
  3. Group A & B————> Meninges & motor neurons (anterior horn cells) causing paralysis
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13
Q

What is the original site of replication in coxsackie ?

A

oropharynx & gastrointestinal tract———-> disseminate via bloodstream

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14
Q

What are the group A diseases & their manifestations?

A
  1. Herpangina
  • fever
  • sore throat
  • Tender vesicles in oropharynx
  1. Hand-foot-and-mouth ( mainly children)
  • Vesicular rash on hands& feets
  • ulceration in mouth
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15
Q

What are the group B diseases & their manifestations?

A
  1. Pleurodynia (Bornholm disease, epidemic myalgia, “devil’s grip”)
    * Fever
    * severe pleuritic-type chest pain
  2. Myocarditis & pericarditis
    * Fever
    * chest pain
    * congestive failure signs
  3. Coxsackie virus B4
    * plays a role in juvenile diabetes
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16
Q

What are the diseases caused by both groups A & B ?

A
  1. Aseptic meningitis:
    * mild paresis
    * acute flaccid paralysis
  2. Upper respiratory infections
  3. Pharyngitis
  4. Minor febrile illnesses with or without rash
17
Q

How to diagnose coxsackie virus ?

A
  1. Isolating virus
    * cell culture or suckling mice
  2. Rise in titer
    * neutralizing antibodies
  3. PCR ( diagnosis of viral meningitis)
    * enteroviral RNA in spinal fluid
18
Q

Important properties of measles virus

A
  • Lipoprotein envelope studded with spikes of 2 transmembrane glycoproteins
  • Helical nucleocapsid
  • Negative single stranded linear non segmented RNA
  • Has RNA dependent RNA polymerase
  • Single stereotype
19
Q

What are the 3 proteins complexed with viral RNA in measles?

A
  1. Nucleocapsid (N) protein:
    * forms helical nucleocapsid
    * represents major internal protein
  2. P (Phosphoprotein) & L (Large polymerase) proteins
  • L & P proteins & nucleocapsid
  • has RNA-dependent activity
  • RNA transcriptase activity
20
Q

What are the 3 proteins that participate in formation of viral envelope of measles ?

A
  1. Matrix (M) protein:
    * underlies viral envelope
    * important in viron assembly

Two transmembrane glycoproteins:

  1. Hemagglutinin (H) :
    * Hemagglutination activities
    * Attachment to host cell
  2. Fusion (F) glycoproteins
    * Membrane fusion
    * Hemolysin activities
21
Q

Transmission of measles virus

A

Respiratory droplets

produced by coughing & sneezing

22
Q

Explain pathogenesis of measles virus

A

virus enters blood & infects reticuloendothelial cells, where it replicates again

Then spreads via blood to skin

23
Q

How rashes occur in measles?

A
  1. Cytotoxic T cells ——-> attack virus–infected vascular endothelial cells in skin
  2. Antibody-mediated vasculitis
  3. Multinucleated giant cells:
    * form as result of fusion protein in spikes
  4. Lifelong immunity occurs
  5. Maternal antibody passes placenta :
    * infants are protected for first 6 months of life
24
Q

How reactivation of dormant organisms & clinical disease is executed by measles virus?

A

Measles virus can transiently depress cell-mediated immunity against other intracellular microorganisms

25
Q

Why measles binds to receptor (CD46) on surface of macrophages?

A

For suppression of interleukin-12 production

(necessary for cell-mediated immunity)

26
Q

What is the Incubation period of measles virus?

A

10 to 14 days

27
Q

What are the symptoms during Prodromal phase of measles?

A
  1. Fever
  2. conjunctivitis
  3. Running nose
  4. Coughing
28
Q

Clinical manifestations for measles virus

A
  1. Koplik’s spots
    * bright red lesions with white , central dot on buccal mucosa
  2. Maculopapular rash
    * appears on face & proceeds gradually down body
    * lower extremities, including palms & soles
29
Q

What are the complications of measles?

A
  1. Encephalitis
  2. Primary measles (giant cell) pneumonia & secondary bacterial pneumonia
  3. Bacterial otitis media
  4. SSPE ( Subacute sclerosing panencephalitis) :
    * rare fatal disease of CNS
    * several years after measles
  5. Measles in pregnant woman leads
    to risk of stillbirth ( birth of an infant that has died in the womb)
30
Q

Diagnosis of measles virus

A
  1. Clinically
  2. Cell culture ( isolation of virus )
  3. Rise antibody titer > fourfold to diagnose difficult cases
  4. PCR

M2 | Microbiolgy (17 decks)

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