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RUSVM Virology > Diagnosis of Viral Infections > Flashcards

Diagnosis of Viral Infections Flashcards

1
Q

Transmission Electron Microscopy

A

Based on transmitted electrons to see what is inside or beyond the surface

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2
Q

Pathogen that can caus human or animal disease but unlikely to be a serious hazard to laboratory workers, the community , livestock or the environment.

Laboratory exposure may cause serious infection, but effective treatment and preventive measures are available and risk of spread of infection is limited

A

Risk Group 2

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3
Q

Mechanism of Action of Immunochromatography

A
  • Ab is immobilized on chromatographic paper, other is labeled with colloidal gold and infiltrated into sample pad
  • Liquid sample is dropped on sample pad, Ag in sample forms an immunocomplex with Ab labled with colloidal gold
  • Complex moves along with the liquid sample makes conact with the Ab immobilized followed by forming an immunocomplex with immobilized Ab generating color
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4
Q

Neutralization

A

Loss of infectivity through reaction of the virus with specific antibody

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5
Q

Competitive ELISA

A

Antigen of interest from the sample and purifed immobilized antigen compete for binding to teh capture antibody. Decrease in signal when compared to assay wells with purified antigen alone indicates the presence of antigens in the sample

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6
Q

Fluorescence Antibody Test (FAT)

A

Antibodies are labelled with a fluorescent dye. Visible fluorescence appears following antigen-antibody reaction

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7
Q

Tissue Homogenization

A

Finely minced and homogenized tissue in glass or mechanical homogenizer

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8
Q

(Transmission/Scanning) electron microscopy produces images with a higher magnification and greater resolution

A

Transmission Electron Microscopy

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9
Q

Electron Microscopy

A

Used to demonstate viruses in sample and detect viruses that cannot be grown in-vitro

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10
Q

Direct FAT

A

Labelled Ab are added onto the samples Ag. Visible fluorescence appears at the binding sites of the specific Ab (Ab-Ag binding)

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11
Q

Complement Fixation Test

A
  • Serum with Ab
  • Ag binds with Ab
  • Complement binds with Ag/Ab complexes
  • Hemolysin sensitized RBCs serve as indicator
  • RBC settle into a pellet
  • No lysis occurs
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12
Q

In negative stain electron microscopy, the virus structure is (white/grey)

A

White

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13
Q

A microorganism that is unlikely to cause human or animal disease

A

Risk Group 1

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14
Q

Typical ELISA

A
  • Antigen coated in a well
  • Antibody tagged with enzyme
  • Antgen binds to enzyme tagged antibody
  • Wash the excess unbound antibodies
  • Add substrate
  • Enzyme tagged to antibody which is bound to antigen will change color
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15
Q

Point of Care (POC)

A

Diagnostic testing performed at or near the patients site of care

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16
Q

Assay

A

Qualittive or quantitative measurement of a target entity/analyte

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17
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

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18
Q

Immunochromatography

A

Form of POC test that is simple to perform, easy to carry and does not require specialized equipment

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19
Q

Direct ELISA

A

Antigens are immobilized and enzyme-conjugated primary antibodies are used to detect or quantify antigen concentration. Specificity of the primary antibody is very important

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20
Q

Indirect Immunohistochemistry Assy

A

Enzyme tagged to a secondary antibody that is specific against primary antibody

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21
Q

Pathogen that usually causes serious human or animal disease and that can be readily transmitted from one individual to another, directly or indirectly. Effective treatment and preventive measures not available

A

Risk Group 4

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22
Q

(Transmission/Scanning) electron microscopy produces three-dimensional images

A

Scanning Electron Microscopy

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23
Q

Immunohistochemistry

A

Ab is tagged with an enzyme. Enzyme reacts with a substance to produce a colored product that can be visualized in the infected cells with a standard light microscope

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24
Q

Mechanism of Competitive Elisa

A
  • Unlabeled Ab incubated in presence of its Ag
  • Bound Ab/Ag complex added to Ag coated well
  • Plate washed, unbound Ab removed
  • Secondary Ab specific to primary Ab is added, second Ab is coupled with an enzyme
  • Substrate is added - enzymes elicit chromogenic or fluorescent signal
  • Reaction is stopped to prevent eventual saturation of signal
  • Weak signal indicates presence of Ag in sample
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25
Q

To prevent spillage it is recommended to follow what system

A

Basic Triple Packaging System

26
Q

Immunoblotting

A
  • Ag separated on gel
  • Blotting tank - proteins transferred to nitrocellulose sheet
  • Specific antigen bind to corresponding labelled antibody
  • Autoradiography
  • Develop and fix autoradiograph
  • Antigen bands visualized
27
Q

Pathogen that usually causes serious human or animal disease but does not ordinarily spread from one infected individual to another. Effective treatment and preventive meaures available.

A

Risk Group 3

28
Q

Diagnostic laborator requires what data

A

Epidemiological Data

Case History

Clinical Signs

29
Q

Gold Standard Test

A

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

30
Q

Characteristics of a BSL-4 Lab

A

Maximum containment

Workers wear one piece, positively air pressurized suit

Negative air pressure mus be maintained in lab rooms

Incoming and outgoing air is HEPA-filtered

Sterilization through double door autoclave

Suit decontamination shower after leaving lab

31
Q

Potential hazards associated wtih transportation of pathogens

A

Breakage of container resulting in spilling

resulting in exposure

Delay in package delivery

32
Q

Plasma

A

Produced when whole blood is collected in tues that are treated with an anticoagulent. Blood does not clot in plasma tube. Cells are then removed by centrifugation

33
Q

Agar Gel Immunodiffusion Test

A
  • Antigen and Antibody placed in separate wells of an agar gell
  • Antigen and Antibody diffuse toward each other
  • Thin white line is formed due to precipitation of antigen/anitbody complex
34
Q

Hemadsorption Inhibition Assay Mechanism

A
  • Infected monolayer cells are incubated with known specific Ab
  • Attempts made to wash away Ab
  • Pretreated monolayer cells are incubated with RBCs - binding is inhibited
35
Q

Biosecurity

A

Laboratory biosecurity 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

36
Q

Positive Predictive Value (PPV)

A

Probability of a positive result accurately indicating the presence of infection

37
Q

Negative Staining Electron Microscopy

A
  • Virus sample is mixed with solution of heavy metal salt that is highly opaque to electrons
  • Mixture is then spread on thin layer on carbon-coated copper grid and dried
  • After bombardment with electron beam, stain absorbs electrons in much higher amounts
38
Q

Indirect FAT

A

IFAT employs secondary antibody labeled with fluorescent marker that recognizes the primary Ab bound to Ag

39
Q

Negative Predictive Value (NPV)

A

Probability that a negative test result accurately indicates the absence of infection

40
Q

Hemadsorption

A

Glycoproteins inserted into host cell membrane at sites of budding of enveloped viruses, allows monolayer cells to adsorb erythrocytes on their cell membranes

41
Q

Plasma - Clotting Factors =

A

Serum

42
Q

Biosafety

A

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

43
Q

Specificity

A

Probability that cases without infection willl have a negative result using the test under evaluation

44
Q

Detection of viruses can be through

A

Culture

Inoculation in eggs

45
Q

Direct Immunohistochemistry Assay

A

Enzyme tagged with primary Ab that binds to Ag, upon successful Ag-Ab binding, tagged enzyme catalyzes substrate to produce color product

46
Q

Biosafety Cabinets (BSC)

A

Enclosed, ventilated laboratory workspace for safely working with material contaminated with pathogens requiring a defined biosafety level

47
Q

Site from which the specimen is collected will be influenced by

A

Clinical signs and knowledge of the pathogenesis of suspected virus

48
Q

Diagnosis of viral infections by gross evaluation involves

A

Clinical Sings

Necropsy

Histopathology

49
Q

Aerosol

A

Very small droplets of fluid that can spread via air

50
Q

Indirect ELISA

A

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

51
Q

Agglutination

A

Method using the property of specific antibodies to bind many antigens into single clumps thereby forming large complexes, whihc are easily precipitated. Precipitation can be macroscopically or microscopically visible

52
Q

Viral Transport Media (VTM)

A

Stabilize the infectivity of specimens, especially swabs. Prevents specimen from drying, helps maintain viral viability and retards growth of microbial contaminants

53
Q

Scanning Electron Microscopy

A

Based on scattered electrons, focuses on the samples surface and composition

54
Q

For virus isolation when is the best time to collect a sample?

A

Soon after the onset of symptoms

________________________

First three days after onset, greatly reduced beyond 5 days

55
Q

Sensitivity

A

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

56
Q

For serological tests when is the best time to collect samples?

A

Two blood specimen

One during the acute phase

Second during the convalescence period

57
Q

Biohazard

A

Biological substance that pose a threat to the health of living organisms, primarily humans

58
Q

Successful detection of viruses from a sample depends on:

A

Collection of sample from correct site

Correct time

Most appropriate animal

Proper transport and storage

Correct diagnostic test

Proper interpretation of results

59
Q

IgM Class-Specific Antibody Assay

A

IgM appear early in infection but drop to low levels within 1-2 months and generally altogether within 3 months, they are usually indicative of recent infection

60
Q

Neutralization Assay

A
  • Presence of unneutralized virus detected
  • Virus and serum mixed under apprpriate conditions and incoculated into cell culture
  • Ag/Ab reaction
  • Ab bound virus becomes non infectious
61
Q

Serum

A

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

62
Q

Hemagglutination and Hemagglutination inhibition method relies on the property of some pathogens to

A

Nonspecifically agglutinate erythrocytes

RUSVM Virology (35 decks)

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