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virology > exam1 DX of virus infections > Flashcards

exam1 DX of virus infections Flashcards

1
Q

T/F viruses never escape the lab.

A 
FALSE!!!!
H1N1 influencza A in china 1977
small pox UK 1978
venezuelan Equine Encephalitis 
Foot and mouth disease in UK
SARS in China
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2
Q 
Which risk group is the highest?
1
2
3
4
A

level 4

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3
Q

which of the following are NOT an example of risk group 2 viruses?

a. herpes virus
b. rabies virus
c. foot and mouth disease
d. adenoviruses

A

b. rabies virus

rabies = risk group 3

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4
Q 
Ebola would be considered which risk group?
1
2
3
4
A

4

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5
Q

T/F in risk level 4 laboratories lab workers should wear a one piece, negatively air pressured air suit.

A

FALSE

in risk level 4 laboratories lab workers should wear a one piece, POSITIVELY air pressured air suit.

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6
Q

In risk level 4 laboratories, the laboratory room should be maintained in :

a. positive air pressure
b. negative air pressure

A

b. negative air pressure

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7
Q

In risk level 4 labs, incoming and outgoing air should be what type of filtered?

A

HEPA

High efficiency particulate air

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8
Q

T/F in risk level 4 labs, it is required to have sterilization through single door autoclaving system.

A

FALSE

in risk level 4 labs, it is required to have sterilization through DOUBLE door autoclaving system.

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9
Q

What is aerosol?

A

very small droplets of fluid that can spread via air.

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10
Q

When is the chance of virus recovery best?

a. during the first 6 days after onset
b. as soon as it is transmitted
c. during the first 3 days after onset

A

c. during the first 3 days after onset

the chance of viral recovery is greatly reduced after 5 days.

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11
Q

For serological tests, two blood samples are collected, one during ___ phase, and the second during ___phase.

a. incubation, prodromal
b. prodromal, decline
c. incubation, convalescent
d. acute, convalescent

A

d. acute, convalescent

varies upon the virus

10-14 days after the first sample.

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12
Q

T/F as a general rule, specimens collected for molecular dx such as PCR, should be obtained during the later part of illness.

A

FALSE
as a general rule, specimens collected for molecular dx such as PCR, should be obtained during the EARLY part of illness.

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13
Q

If collecting blood samples for large animals, how much blood should be collected?

a. 1-5ml
b. 5-10ml
c. 10-15ml
d. 10-20ml

A

d. 10-20ml

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14
Q

If collecting blood samples for small animals, how much blood should be collected?

a. 1-5ml
b. 5-10ml
c. 10-15ml
d. 10-20ml

A

a. 1-5ml

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15
Q

T/F the blood sample for serology should be a clotted sample

A

true

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16
Q

Due to liability of viruses, specimens intended for virus isolation my always be :

a. kept at room temperature
b. kept cold and moist
c. kept cold and dry
d. kept warm and moist

A

b. kept cold and moist

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17
Q

T/F it is preferable to freeze samples rather than refrigerate them.

A

FALSE.
avoid freezing!!

but if you must, then freeze them rapidly at -20C or -70C

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18
Q

T/F specimens for histology should always be frozen

A

FALSE
specimens for histology should NEVER be frozen.

freezing causes ice crystals in the cells.

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19
Q

Which of the following is not a benefit of using Viral Transport Medium (VTM)?

a. prevents specimens from drying
b. helps maintain viral viability
c. retards growth of microbial contaminants
d. all of the above are benefits

A

d. all of the above are benefits

VTM is buffered salt solution added to protein to protect virus against inactivation and prevent multiplication of bact/fungi

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20
Q

Which of the following is NOT a potential hazard in transport of pathogens?

a. breakage of containers
b. exposure to possible infection
c. delay of delivery
d. there are never any issues with transportation

A

d. there are never any issues with transportation

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21
Q 
In processing of tissue sample, for tissue homogenization the sample should be finally minced and homogenized and dilutes in :
a. 1:5
b 1:10
c 1:20
d 1:50
A

b 1:10

and centrifuged at 10,000 for 15 minutes

22
Q

T/F in processing swabs, twirl the swab in the VTM and vortex the VTM in the vial. this should leave inoculate cultures

A

true

23
Q

What is the simplest way to diagnose a virus?

A

by the clinical signs

24
Q

What is cytopathic effect?

A

damage or morphological changes to host cells during virus invasion

25
Q

T/F TEM is used to detect viruses that cannot be grown in-vitro

A

true

26
Q

Explain the process negative-stain electron microscopy.

A

virus sample mixed with solution of heavy metal salt that is highly opaque to electrons
(sodium phosphotungstate or uranyl acetate)
mixture spread on thin layer on a carbon coated copper grid and dried

27
Q

What are the advantages of TEM over SEM?

a. higher magnification
b. greater resolution
c. lower cost
d. both a and b

A

d. both a and b

28
Q

What is the advantage of SEM over TEM?

A

3D imaging

29
Q

TEM :

a. focuses on the sample’s surface and its composition
b. seeks to see what is inside or beyond surface

A

b. seeks to see what is inside or beyond surface

30
Q

SEM :

a. focuses on the sample’s surface and its composition
b. seeks to see what is inside or beyond surface

A

b. seeks to see what is inside or beyond surface

31
Q

What is an assay?

A

qualitative or quantitative measurement of a target entity, such as drug or biomolecule

32
Q

Define gold standard test

A

dx test that is considered to be the most accurate and best available

33
Q

Negative predictive value (NPV) is

a. probability of a negative test result accurately indicates the absence of infection.
b. probability of a positive test result accurately indicates the absence of infection.

A

a. probability of a negative test result accurately indicates the absence of infection.

34
Q

Positive predictive value (PPV) is

a. probability of a negative test result accurately indicates the absence of infection.
b. probability of a positive test result accurately indicates the absence of infection.

A

b. probability of a positive test result accurately indicates the absence of infection.

35
Q

Sensitivity is :

a. percentage that cases with infection will have a positive result using the test under evaluation
b. percentage that cases without infection will have a negative result using the test under evaluation

A

a. percentage that cases with infection will have a positive result using the test under evaluation

36
Q

Specificity is :

a. percentage that cases with infection will have a positive result using the test under evaluation
b. percentage that cases without infection will have a negative result using the test under evaluation

A

b. percentage that cases without infection will have a negative result using the test under evaluation

37
Q

What type of tube should serum be collected in?

a. tiger top
b. lavender
c. red top

A

c. red top

38
Q

Serum is :

a. produced when whole blood is collected in tubes treated with and anticoagulant
b. clear yellowish fluid obtained upon separating whole blood into its solid and liquid components after it has been allowed to clot

A

b. clear yellowish fluid obtained upon separating whole blood into its solid and liquid components after it has been allowed to clot

39
Q

Plasma is :

a. produced when whole blood is collected in tubes treated with and anticoagulant
b. clear yellowish fluid obtained upon separating whole blood into its solid and liquid components after it has been allowed to clot

A

a. produced when whole blood is collected in tubes treated with and anticoagulant

blood does not clot in lavender EDTA tube.
cells are removed by centrifugation.

plasma - 55%
buffy coat -

40
Q

Direct ELISA :

a. antigens are immobolized and enzyme-conjugated primary antibodies are used to detect antigen concentration.
b. primary antibodies are not labeled, but detected instead with enzyme-conjugated secondary antibodies that recognize the primary antibodies

A

a. antigens are immobilized and enzyme-conjugated primary antibodies are used to detect antigen concentration.

specificity of the primary antibody is very important

41
Q

Indirect ELISA :

a. antigens are immobolized and enzyme-conjugated primary antibodies are used to detect antigen concentration.
b. primary antibodies are not labeled, but detected instead with enzyme-conjugated secondary antibodies that recognize the primary antibodies
c. antigen of interest from the sample and purified immobolized antigen compete for binding to the capture antibody.
d. antigen to be measured is bound between a layer of capture antibodies and a layer of detection antibodies

A

b. primary antibodies are not labeled, but detected instead with enzyme-conjugated secondary antibodies that recognize the primary antibodies

42
Q

Sandwich ELISA :

a. antigens are immobolized and enzyme-conjugated primary antibodies are used to detect antigen concentration.
b. primary antibodies are not labeled, but detected instead with enzyme-conjugated secondary antibodies that recognize the primary antibodies
c. antigen of interest from the sample and purified immobolized antigen compete for binding to the capture antibody.
d. antigen to be measured is bound between a layer of capture antibodies and a layer of detection antibodies

A

d. antigen to be measured is bound between a layer of capture antibodies and a layer of detection antibodies

the two antibodies must be carefully selected so not to get cross reactivity or competition of binding site

43
Q

Competitive ELISA :

a. antigens are immobolized and enzyme-conjugated primary antibodies are used to detect antigen concentration.
b. primary antibodies are not labeled, but detected instead with enzyme-conjugated secondary antibodies that recognize the primary antibodies
c. antigen of interest from the sample and purified immobolized antigen compete for binding to the capture antibody.
d. antigen to be measured is bound between a layer of capture antibodies and a layer of detection antibodies

A

c. antigen of interest from the sample and purified immobolized antigen compete for binding to the capture antibody.

a decrease in signal when compared to assay wells with purified antigen along indicates the presence of antigens in sample

44
Q

In fluorescence antibody test (FAT) what appears following antigen-antibody reaction?

A

visible fluorescence

45
Q

T/F in immunohistochemiisty, the antibody is tagged with an enzyme, generally horseradish peroxidase.

A

true.

the enzyme reacts with a substrate to produce a colored produce that can be visualized in the infected cell with a microscope

46
Q

What is an immunochromatography?

A

lateral flow devices.
A form of POC (point of care) tests that is simple to perform, no special equipment.

ex : pregnancy test, HIV test

samples will test positive that have antigens present

47
Q

What is agglutination?

A

method using property of specific antibodies to bind many antigens into single clumps, forming large complexes which are easily precipitates.

48
Q

T/F hemagglutination tests have been used extensively for detection of serotype specific antibodies against avian influenza

A

true

49
Q

How do we know if of the agar gel immunodiffusion test is positive?

A

precipitates will form when antigen diffuses through the antibody matrix.

ex : avian influenza - matrix antibodies
equine infectious anemia - coggins test

50
Q

What is complex fixation test used for?

A

quantitation of serum Ab levels.

absence of lysis = positive result

51
Q

T/F hemadsorption is a phenomenon where monlayer cells absorb leukocytes on their cell membranes.

A

FALSE
hemadsorption is a phenomenon where monolayer cells absorb ERYTHROCYTES on their cell membranes.

occurs once glycoproteins have inserted into host cell membrane at sites of budding of enveloped viruses.

52
Q

T/F lgG antibodies are usually indicative of recent infection.

A

FALSE

IgM - appear early after infection but drop to low levels within 1-2 months and disappear altogether within 3 months

virology (8 decks)

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