Podcast
Questions and Answers
What characteristic viral feature is primarily used to identify viruses in electron microscopy?
What characteristic viral feature is primarily used to identify viruses in electron microscopy?
Morphology and size.
Why are specimens negatively stained with potassium phosphotungstate in electron microscopy?
Why are specimens negatively stained with potassium phosphotungstate in electron microscopy?
To enhance contrast and visualize the viral structure.
Why is low sensitivity a significant disadvantage of using electron microscopy for virus detection?
Why is low sensitivity a significant disadvantage of using electron microscopy for virus detection?
A high viral load of 10^7 particles/mL is required for detection.
How does immuno-electron microscopy enhance the detection process compared to standard electron microscopy?
How does immuno-electron microscopy enhance the detection process compared to standard electron microscopy?
What type of stain is used to visualize viral antigens in skin biopsies using fluorescent microscopy?
What type of stain is used to visualize viral antigens in skin biopsies using fluorescent microscopy?
In fluorescent microscopy, what is meant by a 'syndromic approach' for diagnosing respiratory infections?
In fluorescent microscopy, what is meant by a 'syndromic approach' for diagnosing respiratory infections?
What are inclusion bodies, and how do they alter the staining property of a host cell when observed under light microscopy?
What are inclusion bodies, and how do they alter the staining property of a host cell when observed under light microscopy?
In light microscopy, what are the two primary types of inclusion bodies based on their location within the cell?
In light microscopy, what are the two primary types of inclusion bodies based on their location within the cell?
What staining methods are mentioned that can be used to visualize certain intracytoplasmic inclusion bodies?
What staining methods are mentioned that can be used to visualize certain intracytoplasmic inclusion bodies?
How did Cowdry classify intranuclear inclusion bodies, and what are the key characteristics of each type?
How did Cowdry classify intranuclear inclusion bodies, and what are the key characteristics of each type?
Give 2 examples of intracytoplasmic inclusion bodies and the viruses they are associated with.
Give 2 examples of intracytoplasmic inclusion bodies and the viruses they are associated with.
Provide two examples of intranuclear inclusion bodies and the viruses they are associated with.
Provide two examples of intranuclear inclusion bodies and the viruses they are associated with.
What is the role of hydrogen peroxide in immunoperoxidase staining for viral antigen detection?
What is the role of hydrogen peroxide in immunoperoxidase staining for viral antigen detection?
What is the purpose of collecting nasopharyngeal aspirates in antigen detection immunofluorescence for respiratory viruses?
What is the purpose of collecting nasopharyngeal aspirates in antigen detection immunofluorescence for respiratory viruses?
The direct detection of viruses offers rapid diagnostic methods. What is a key advantage of these methods in clinical settings?
The direct detection of viruses offers rapid diagnostic methods. What is a key advantage of these methods in clinical settings?
How are direct detection methods particularly beneficial in acute cases, providing an example?
How are direct detection methods particularly beneficial in acute cases, providing an example?
What is the role of specific antiviral antibodies?
What is the role of specific antiviral antibodies?
What are three examples of shapes that can be seen in a virus using electron microscopy?
What are three examples of shapes that can be seen in a virus using electron microscopy?
What is a limitation of electron microscopy related to cost?
What is a limitation of electron microscopy related to cost?
Give 2 examples of direct detection methods that tests the antigens of a virus.
Give 2 examples of direct detection methods that tests the antigens of a virus.
Give 2 examples of direct detection methods that use the power of a microscope to view a viral sample.
Give 2 examples of direct detection methods that use the power of a microscope to view a viral sample.
In light microscopy, describe generally what is seen in the tissue section.
In light microscopy, describe generally what is seen in the tissue section.
Are both electron microscopy and immuno-electron microscopy considered direct detection methods? Why or why not?
Are both electron microscopy and immuno-electron microscopy considered direct detection methods? Why or why not?
Other than diagnostic purposes, give other reasons direct detection meethods are important.
Other than diagnostic purposes, give other reasons direct detection meethods are important.
Direct detection involves the usage of some diagnostic method/s, what is the specimen used for detection of viral components?
Direct detection involves the usage of some diagnostic method/s, what is the specimen used for detection of viral components?
Flashcards
Direct Detection
Direct Detection
Rapid diagnostic methods that give results within a day.
Electron Microscopy (EM)
Electron Microscopy (EM)
Identifying viruses by morphology and size using an electron beam.
Potassium Phosphotungstate
Potassium Phosphotungstate
A stain used in electron microscopy to negatively stain specimens.
Immuno-electron Microscopy
Immuno-electron Microscopy
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Fluorescent Microscopy
Fluorescent Microscopy
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Inclusion Bodies
Inclusion Bodies
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Intracytoplasmic Inclusion
Intracytoplasmic Inclusion
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Intranuclear Inclusion
Intranuclear Inclusion
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Pink Structures
Pink Structures
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Cowdry Type A Inclusions
Cowdry Type A Inclusions
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Cowdry Type B Inclusions
Cowdry Type B Inclusions
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Rabies virus
Rabies virus
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Owl's eye inclusion bodies
Owl's eye inclusion bodies
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Immunoperoxidase Staining
Immunoperoxidase Staining
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Hydrogen Peroxide
Hydrogen Peroxide
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Antigen Detection Immunofluorescence
Antigen Detection Immunofluorescence
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Study Notes
- Direct detection methods are rapid diagnostic methods
- Direct detection provides results within the same day or the next day
- Detection of viral components can be done in cells from infected tissues or in fluid specimens
- Direct detection is useful in acute cases like diagnosing RSV infection in neonates or severe CMV infections in immunocompromised patients
Direct Detection Tests
- Electron Microscopy
- Immune electron microscopy
- Fluorescent Microscopy
- Light microscopy
- Antigen detection immunofluorescence, ELISA etc
- Molecular techniques for the direct detection of viral genomes.
Electron Microscopy (EM)
- EM identifies viruses by morphology and size
- Specimens are negatively stained by potassium phosphotungstate and scanned under EM
- Viruses must be present in a sufficient quantity (107 particles/mL) to be detected
- EM drawbacks: high cost, low sensitivity, threshold detection of 10 virions/mL, and low specificity
- Rabies virus is bullet shaped
- Coronavirus is petal shaped
- Rotavirus wheel shaped
- Adenovirus is space vehicle shaped
- Astrovirus is star shaped
Immuno-electron Microscopy
- Sensitivity and specificity of EM is improved by adding specific antiviral antibodies
- Antibodies aggregate the virus particles, which are then centrifuged
- The sediment is negatively stained and viewed under EM
Fluorescent Microscopy
- Specimen placed on a slide then stained using a specific antiviral antibody tagged with fluorescent dye
- Viewed under a fluorescent microscope
- Used in diagnosis of rabies virus antigen in skin biopsies, adenovirus from corneal smear of infected patients
- Syndromic approach allows for rapid diagnosis of respiratory infections
Light Microscopy
- Inclusion bodies are aggregates of virions or viral proteins/products of viral replication
- Confer altered staining property to the host cell
- Inclusion bodies have distinct size, shape, location, and staining properties
- Able to be demonstrated in virus-infected cells under the light microscope
- Histopathological staining of tissue sections used for detection of inclusion bodies
- The two types: intracytoplasmic and intranuclear
- Pink structures are seen with Giemsa or eosin methylene blue stains in intracytoplasmic regions
- Cowdry classified intranuclear inclusions into two categories in 1934
- Cowdry type A inclusions are variable in size and have a granular appearance
- Cowdry type B inclusions are more circumscribed and multiple
Examples of Inclusion bodies
- Intracytoplasmic inclusion bodies:
- Negri bodies associated with rabies virus
- Molluscum bodies associated with Molluscum contagiosum virus
- Guarnieri bodies associated with Vaccinia virus
- Bollinger bodies associated with Fowl pox virus
- Perinuclear cytoplasmic acidophilic bodies associated with Reovirus
- Intranuclear inclusion bodies:
- Owl's eye inclusion bodies associated with Cytomegalovirus
- Cowdry type A inclusion bodies associated with Herpes simplex virus and measles virus
- Intranuclear basophilic associated with Adenovirus
- Acidophilic inclusion bodies associated with Papovavirus
Immunoperoxidase Staining
- Tissue sections or cells coated with viral antigens are stained with antibodies tagged with horseradish peroxidase
- Hydrogen peroxide and a coloring agent (benzidine derivative) is added
- The resulting color complex can be viewed under a light microscope
Antigen Detection Immunofluorescence
- Nasopharyngeal aspirates are used for respiratory viruses like RSV, flu, and adenoviruses
- Useful in detection of rotavirus antigen in feces
- Useful in detection of viruses in skin scraping
- Useful in detection of HBsAg in serum
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