lecture 12

Question 1

Risk group 1- classification of infective microorganisms

Answer 1

no or low individual and community risk

Question 2

risk group 2

Answer 2

moderate individual risk, low community risk

Question 3

risk group 3

Answer 3

• 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

Question 4

risk group 4

Answer 4

• 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

Question 5

BSL-4

Answer 5

• maximum containment laboratory

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

Question 6

biohazard

Answer 6

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

Question 7

biosafety

Answer 7

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

Question 8

aerosol

Answer 8

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

Question 9

biosecurity

Answer 9

-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

Question 10

sample collection for virus isolation

Answer 10

• 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

Question 11

timing of sample collection for serological tests

Answer 11

-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)

Question 12

timing of sample collection for molecular diagnostics

Answer 12

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

Question 13

Viral transport

Answer 13

• viral transport medium (VTM)- swabs

- basic triple packaging system to prevent spillage of infectious materials

Question 14

diagnosis of viral infections by gross evaluation and histopathology

Answer 14

• clinical signs
• necropsy
• histopathology

Question 15

detection of viruses by cultivation/isolation

Answer 15

• in cell tissue/culture

- inoculation in eggs

Question 16

electron microscopy

Answer 16

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

Question 17

transmission electron microscopy

Answer 17

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

Question 18

scanning electron microscopy

Answer 18

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

Question 19

gold standard of serological assay

Answer 19

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

Question 20

sensitivity of assay

Answer 20

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

Question 21

specificity of assay

Answer 21

-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

Question 22

what color top do you use for collection of serum?

Answer 22

red-top vacutainer tube

Question 23

plasma

Answer 23

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

Question 24

what color top do you use when collecting plasma?

Answer 24

lavender top EDTA vacutainer tube

Question 25

enzyme-linked immunosorbent assay (ELISA)

Answer 25

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

Question 26

direct ELISA

Answer 26

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

Question 27

indirect ELISA

Answer 27

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

Question 28

sandwich ELISA

Answer 28

- 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

Question 29

competitive ELISA

Answer 29

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

Question 30

direct fluorescence antibody test (FAT)

Answer 30

- labelled antibodies are added onto the sample (antigen) | - visible fluorescence appears at the binding sites of the specific antibodies (antigen-antibody binding)

Question 31

indirect fluorescence antibody test (IFAT)

Answer 31

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

Question 32

immunohistochemistry

Answer 32

- 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

Question 33

immunochromatography (lateral flow devices)

Answer 33

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

Question 34

hemagglutination and hemagglutination inhibition test

Answer 34

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

Question 35

agar gel immunodiffusion test

Answer 35

- 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

Question 36

complement fixation test

Answer 36

- 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

Question 37

neutralization assays

Answer 37

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