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virology > lecture 12 > Flashcards

lecture 12 Flashcards

1
Q

Risk group 1- classification of infective microorganisms

A

no or low individual and community risk

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2
Q

risk group 2

A

moderate individual risk, low community risk

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3
Q

risk group 3

A
  • high individual risk, low community risk
  • usually causes serious human or animal disease but does not ordinarily spread from one infected individual to another
  • effective treatment and preventive measures are available
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4
Q

risk group 4

A
  • pathogen that usually causes serious human or animal disease that can be readily transmitted from one individual to another, directly or indirectly.
  • effective treatment and preventive measures usually not available
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5
Q

BSL-4

A
  • maximum containment laboratory

- handle dangerous and exotic pathogens belonging to the highest risk group (risk group 4) such as ebola virus

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6
Q

biohazard

A

biological substances that pose a threat to the health of living organisms, primarily that of humans

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7
Q

biosafety

A

laboratory biosafety describes the containment principles, technologies, and practices that are implemented to prevent the unintentional exposure to pathogens and toxins, or their accidental release

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8
Q

aerosol

A

very small droplets of fluid that can spread via air. Viruses can spread in lab through aerosol route

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9
Q

biosecurity

A

-describes the protection, control, and accountability for valuable biological materials within laboratories, in order to prevent their unauthorized access, loss, theft, misuse, diversion, or intentional release

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10
Q

sample collection for virus isolation

A
  • specimens should be collected as soon after onset of symptoms as possible, because maximal amounts (titers) of virus are usually present at the onset of signs
  • chance of viral recovery is best during the first three days after onset, and is greatly reduced beyond 5 days with viruses
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11
Q

timing of sample collection for serological tests

A

-two blood specimens are generally collected- one during acute phase of illness and second during convalescence period (varies upon type of virus 10-14 days after 1st sample or even more)

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12
Q

timing of sample collection for molecular diagnostics

A

-specimens such as for PCR should be obtained during early part of illness

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13
Q

Viral transport

A
  • viral transport medium (VTM)- swabs

- basic triple packaging system to prevent spillage of infectious materials

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14
Q

diagnosis of viral infections by gross evaluation and histopathology

A
  • clinical signs
  • necropsy
  • histopathology
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15
Q

detection of viruses by cultivation/isolation

A
  • in cell tissue/culture

- inoculation in eggs

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16
Q

electron microscopy

A

-can be used to demonstrate viruses in samples and detect viruses that cannot be grown in-vitro

17
Q

transmission electron microscopy

A
  • based on transmitted electrons
  • seeks to see what is inside or beyond the surface
  • advantages: have higher magnification and greater resolution
18
Q

scanning electron microscopy

A
  • based on scattered electrons
  • focuses on sample’s surface and its composition
  • advantage: produces 3-d images
19
Q

gold standard of serological assay

A

-diagnostic test that is considered to be most accurate and best available under a particular condition or set of conditions

20
Q

sensitivity of assay

A

probability (percentage) that cases with the infection (determined by the result of the reference or “gold standard” test) will have positive result using the test under evaluation

21
Q

specificity of assay

A

-probability (percentage) that cases without the infection (determined by the result of the reference or “gold standard” test) will have a negative result using the test under evaluation

22
Q

what color top do you use for collection of serum?

A

red-top vacutainer tube

23
Q

plasma

A

produced when whole blood is collected in tubes treated with anticoagulant, blood does not clot in plasma tube

24
Q

what color top do you use when collecting plasma?

A

lavender top EDTA vacutainer tube

25
Q

enzyme-linked immunosorbent assay (ELISA)

A

typical ELISA:

  1. antigen coated in a well
  2. add antibody tagged with an enzyme
  3. antigen binds to enzyme-tagged antibody
  4. wash the excess unbound antibodies
  5. add substrate
  6. enzyme tagged to antibody which is bound to antigen will change color of substrate, intensity of color indicates more positive reaction
26
Q

direct ELISA

A
  • antigens are immobilized and enzyme-conjugated primary antibodies are used to detect or quantify antigen concentration
  • specificity of primary antibody is very important
27
Q

indirect ELISA

A

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

28
Q

sandwich ELISA

A
  • antigen to be measured is bound between a layer of capture antibodies and a layer of detection antibodies
  • two antibodies must be very critically chosen to prevent cross-reactivity or competition of binding sites
29
Q

competitive ELISA

A

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

30
Q

direct fluorescence antibody test (FAT)

A
  • labelled antibodies are added onto the sample (antigen)

- visible fluorescence appears at the binding sites of the specific antibodies (antigen-antibody binding)

31
Q

indirect fluorescence antibody test (IFAT)

A

-employs a secondary antibody labeled with a fluorescent marker that recognizes the primary antibody bound to antigen

32
Q

immunohistochemistry

A
  • antibody is tagged with an enzyme, generally horseradish peroxidase
  • the enzyme reacts with a substrate to produce a colored product that can be visualized in the infected cells with a standard light microscope
33
Q

immunochromatography (lateral flow devices)

A

-form of point of care test that is simple to perform, easy to carry, and does not require specialized equipment

34
Q

hemagglutination and hemagglutination inhibition test

A

-method relies on the property of some pathogens (mainly viruses) to nonspecifically agglutinate erythrocytes

35
Q

agar gel immunodiffusion test

A
  • antigen and antibody are placed in separate wells of agar gel
  • antigen and antibody diffuse toward each other
  • thin white line is formed due to precipitation of antigen/antibody complex
36
Q

complement fixation test

A
  • positive reaction: has antibodies against the bottom, there is no lysis of RBCs and they settle to bottom of test tube
  • negative reaction: has no antibodies, there will be destruction and hemolysis of the RBCs
37
Q

neutralization assays

A

-defined as the loss of infectivity through reaction of the virus with specific antibody

virology (12 decks)

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