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MICBI Virology > T04 Viral diagnostics > Flashcards

T04 Viral diagnostics Flashcards

1
Q

What is the FA technique?

A

Fluorescent antibody technique
- specialized serological procedure which consists of antigen-antibody reaction made visible by a fluorescent dye incorporated into the system

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2
Q

To test for an antibody by FA technique,

  1. Microbial antigens are dried and fixed on glass slides
  2. Dilutions of test serum are incubated with the antigen
  3. Slides are rinsed and fluorescein-labeled antiglobulin is added.
  4. After slides are rinsed and dried, examine under the fluorescence microscope.
A

just read ~

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3
Q

Name a G- bacilli in which its antigen is commonly tested by FA technique.

A 
Legionella pneumophilia 
- cultured by BCYE (buffered-charcoal-yeast-extract)
\+ 5% CO2 
- found in stagnant water
- causes atypical pneumonia
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4
Q

The respiratory syncytial virus produces multinucleated giant cells/syncytia during its replication in HEp2 cell cultures.
This is an example of ______________. What does it mean?

A

Cytopathic effect

  • infection of cells with a virus that gives rise to a change in morphology of the cell
  • e.g. rounding up of cell > grape-like appearance
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5
Q

Other than RSV, give 3 examples that cytopathic effect can be observed.

A
  1. Poliovirus in LLC Monkey kidney cells
  2. HSV (Herpes Simplex Virus) in fetal lung cells
  3. Adenovirus in HEp2 cells
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6
Q

What is the top differential diagnosis (virus) for Myocarditis?

A

Coxsackie virus

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7
Q

What test can be done to test for Coxsackie virus in myocarditis?
Describe the test (2).

A

Neutralization test

  • Mixing patient’s serum (with virus-neutralizing antibodies) with a suspension of virus > inoculating into either animal/tissue cultures
  • Observe any cytopathic effects, i.e. infected due to no specific neutralizing antibodies
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8
Q

Haemoadsorption can be used to identify what virus?

A
  • Influenza A,B, and parainfluenza 1,2 and 3
  • they possess haemagglutinin on their virus envelope, which will be present on cell sheets infected by the virus.
  • Cell sheet adsorb/ agglutinate erythrocytes
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9
Q

Electron microscopy is used to observe the morphology of the virus. What are the limitations?

A
  • Viruses from the same group cannot be distinguished

- Identification of virus is usually up to family level

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10
Q

List 3 members of the family Reoviridae which all cause gastroenteritis.

A

Rotavirus, reovirus, orbivirus

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11
Q

List some features on EM of rotavius.

A
  1. Monomorphic
  2. Double shell
  3. Peripheral spikes form the inner layer
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12
Q

Members of Adenoviridae that causes respiratory/eye infection?

A

Adenovirus types 1-47

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13
Q

Which of the following about adenovirus on EM is incorrect?
A. It has double-stranded DNA
B. It is monomorphic and non-enveloped
C. 70-75mm capsid with 252 capsomers
D. Outline frequently looks hexagonal and triangular faces
E. Star of David (six-pointed star with a central hollow) is the characteristic feature

A

E

Should be Calicivirus

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14
Q

Calicivirus is from the family of Caliciviridae, which causes GE-like diseases.
It is monomorphic, 31-35mm in size.
What is its characteristic feature?

A

“Star of David”, a six-pointed star with a central hollow

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15
Q

What family does Hepatitis B virus belong to?

A

Hepadnaviridae

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16
Q

What are the distinct morphological features of Hep B virus on EM? (3)

A

3 distinct particles
1. Dane particles: whole hepatitis B virion composed of envelope (circular and big in shape, 40-45nm)

  1. Spherical form: 18-22nm, HBsAg (=Dane particles but without any core/nucleic acid)
  2. Tubular/filamentous form: 18-22nm, self-assembled surplus coat proteins
17
Q

Give viruses that belong to the Herpesviridae family. (5)

A
  1. Herpes Simplex Virus 1 & 2
  2. Varicella-zoster virus
  3. Cytomegalovirus
  4. Epstein-Barr virus
  5. Human herpesvirus 6,7,8
18
Q

Give characteristic features of Herpesviride family on EM. (4)

A

95-105 nm (big)

  1. Enveloped
  2. Monomorphic
  3. Hollow tubes giving a castellated edge at the periphery
  4. Rings in the center

(like fried egg)

19
Q

What is the family of Influenza A,B and C?

A

Orthomyxoviridae

20
Q 
Orthomyxoviridae is
A. Monomorphic
B. has variable size (80-120m)
C. is a single stranded RNA
D. Helical in symmetry 
E. Enveloped

What is the characteristic feature of its virus on EM?

A

All except A
- Pleomorphic

  • 10nm surface spikes form a characteristic fringe at the periphery
21
Q

What viruses are in the Papovaviridae family?

A
  1. Human papillomavirus

2. Polymavirus (JC, BK virus)

22
Q

Which of the following about Human papillomavirus on EM is incorrect?
A. They are monomorphic
B. They are non-enveloped
C. They are 45-55nm capsid with 74 capsomers in the skew arrangement
D. Capsomers are more visible on one side of the particle than the other because of the skew nature
E. They are double-stranded RNA

A

E
should be double-stranded DNA
(Only Reovirus is double-stranded RNA)

B: yes, only Papillomavirus and Adenovirus are naked dsDNA

23
Q

This family is pleomorphic, with variable size 90-300m, enveloped ssRNA.

It also has a peripheral fringe but is shorter than orthomyxovirus. The individual spikes are less clear too.
The virion break open readily, releasing a “herringbone-like” internal ribonucleoprotein helix.

What is the family?

A

Paramyxoviridae

24
Q

List viruses in the Paramyxoviridae family. (4)

A
  1. Parainfluenza virus type 1,2,3,4a,4b
  2. Respiratory syncytial virus
  3. Measles
  4. Mumps
25
Q

Members of the Poxiviridae family?

- dsDNA

A
  1. Variola (smallpox)
  2. Cowpox
  3. Monkeypox
  4. Vaccinia virus
26
Q

What is the characteristic morphology of Poxiviridae family?

A

Dimorphic
M= mulberry (入面白色+thread-like）
C= capsule (入面黑色）

  • enveloped, 250-200nm
  • thread-like structures over the surface of M form
27
Q

What can be used to detect HBeAg in human serum? (1)

HBeAg = viral protein of Hep B

Describe the process. (4)

A

Use of ELISA
- Enzyme-linked Immunosorbent Assay

  1. Wells coated with Anti-HBe + Patient’s serum
    • Enzyme-linked Anti-HBe
  3. washing (unbound enzymes will be washed off)
  4. if there is substrate binding to enzyme E = positive = brown color
28
Q

What is Latex agglutination test?

A
  1. Latex particles coated with Antigens
  2. Specific antibodies are added
  3. Agglutination (clumping)
29
Q

In real time PCR, the higher the level of viral RNA/DNA, the __________ the CT value (threshold cycle).
What is the advantage of real-time PCR compared to a conventional PCR?

A

Smaller.

Can determine the initial amount of DNA/cDNA target with great precision. (Quantification)

MICBI Virology (9 decks)

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