Diagnosis of Viral Infections Flashcards
Which risk group would an organism be in if it had no or low individual and community risk?
Risk Group 1
Which risk group would an organism be in if it had moderate individual risk but low community risk?
Risk Group 2
Which risk group would an organism be in if it had high individual risk but low community risk?
Risk Group 3
Which risk group would an organism be in if it had high individual and community risk?
Risk Group 4
What type of lab is the maximum containment lab, and handles dangerous and exotic pathogens belonging to risk group 4?
BSL-4 lab
Safety practices implemented within the lab are collectively known as:
Biosafety
Protection and control of the biological materials within a lab to prevent misuse or unauthorized access:
Biosecurity
Samples for virus isolation should be collected when titers are at their highest, which is at what point in infection?
At the onset of clinical signs
For serological testing, when are the 2 blood samples taken?
During the acute phase and during the convalescent phase
Samples collected for molecular diagnostics (PCR) should be collected when?
During the early part of the illness
Viral transport media consists of what?
Sterile vials and swabs
To prevent spillage during transport of samples, how many packages are recommended?
3
What are the 3 general methods of identifying viral diseases?
Clinical signs
Necropsy
Histopathology
What are the 2 ways to cultivate/isolate viruses?
Tissue culture
Inoculation in eggs
How can viruses that can’t be grown in-vitro be detected?
Electron microscopy
What is the method and focus of TEM?
Method: transmitted electrons
Focus: see what’s inside
What is the method and focus of SEM?
Method: scattered electrons
Focus: sample’s surface and conposition
(SEM/TEM) can produce images with higher magnification and greater resolution?
TEM
What is the advantage to using SEM over TEM in some scenarios?
SEM produces a 3D image, while TEM only produces a 2D image
If the probability that a test has a high rate of detecting true positives, the test has a high ______.
Sensitivity
If a test has a high probability of finding true negatives, the sample has a high ______.
Specificity
Collection of serum is done with a _____ top tube.
Red
Collection of plasma is done with a ______ top tube, or a tube with ______.
Purple; anticoagulant (EDTA)
What kind of serological test uses enzyme-coated antibodies and a substrate to detect viral infections?
ELISA
In what type of ELISA is the specificity of the primary Ab very important because it is the only one used?
Direct
In what type of ELISA are the primary Ab not labeled, but detected by a second, enzyme-conjugated, Ab that recognizes the primary Ab?
Indirect
What type of ELISA uses a capture Ab and a detection Ab, which surround the Ag to be detected?
Sandwich
Why is it important to choose the capture and detection Ab so carefully in sandwich ELISA?
Prevent cross reactivity or competition for binding sites
For which type of ELISA does a decrease in signal (or less of a color change) indicate the presence of Ag in the sample?
Competitive
What type of serological test works similar to ELISA but uses a fluorescent dye such as fluorescein to label the antibodies instead of an enzyme?
Fluorescence Antibody Test
Direct FAT
Indirect FAT
What serological test uses an enzyme like Horseradish Peroxidase, which will react with a substrate and produce a color change that can be viewed with a light microscope?
Immunohistochemistry
Benefits of lateral flow testing devices
Point-of-care
Easy
Fast
No special equipment
What serological test relies on the ability of specific Ab to bind many Ag into clumps that can be viewed macro- or microscopically.
Agglutination
What serological test relies on the ability of certain viruses to non-specifically agglutinate erythrocytes?
Hemagglutination
What is an OIE recommended test that involves placing Ag and Ab in separate wells on an agar gel and looking for a white precipitate line between them, indicating formation of Ab/Ag complexes?
Agar Gel Immunodiffusion Test
T/F: Agar Gel Immunodiffusion test is OIE recommended.
TRUE
How is a positive result indicated in the Complement fixation test?
RBCs settle to the bottom of the tube because complement has been binded to Ab/Ag complex and there is none left free to hemolyze the blood.
How is a negative result indicated in the Complement fixation test?
Hemolysis of RBCs in the tube because, since there is no Ag, there are no Ag/Ab complexes for the complement proteins to bind, and they are free in the sample.
_______ is the loss of virus infectivity due to reaction of the virus with a specific Ab.
Neutralization
