Micro 39 Flashcards

A child develops aseptic meningitis in summer. Which viral category is most strongly suggested?

A. HSV or VZV infection
B. CMV or rabies infection
C. Arbovirus or enterovirus infection
D. Influenza or adenovirus infection

A patient develops fever, focal seizures, and temporal-lobe encephalitis. Which virus is most likely?

A. Herpes simplex virus
B. West Nile virus
C. Poliovirus
D. JC virus

Urine sediment from an immunosuppressed patient contains enlarged cells with intranuclear basophilic inclusions. Which finding is characteristic?

A. Cowdry type A inclusions
B. Cytoplasmic Negri bodies
C. Multinucleated giant cells
D. Owl’s-eye nuclear inclusions

Which method is routinely used for viral isolation in clinical laboratories?

A. Embryonated eggs
B. Tissue culture
C. Electron microscopy
D. Serologic testing

What is the principal modern use of embryonated eggs in virology?

A. Detecting rabies inclusions
B. Measuring viral titers
C. Producing influenza vaccines
D. Diagnosing HSV encephalitis

Which description best characterizes diploid cell lines?

A. Finite passages before senescence
B. Indefinite passages without senescence
C. Mixed cells from fresh tissue
D. Nondividing cells from urine

When should a specimen for viral isolation ideally be collected?

A. After antibody titers peak
B. During late convalescence
C. After viral shedding ends
D. Early during acute infection

Which property characterizes tumor and immortalized cell lines?

A. Rapid senescence after isolation
B. Indefinite passage without senescence
C. Multiple unrelated cell types
D. Direct collection from tissues

Why should viral specimens be transported and stored on ice?

A. Capsids dissolve at room temperature
B. Cold increases viral replication
C. Enveloped viruses are less stable
D. Ice activates viral hemagglutinin

Which viral group commonly promotes syncytium formation?

A. Paramyxoviruses, HSV, VZV, HIV
B. Adenoviruses, HPV, CMV, rabies
C. Rotaviruses, noroviruses, polioviruses, JC virus
D. Parvovirus, HBV, HCV, rubella

HSV and VZV infections cells contain eosinophilic nuclear inclusions with surrounding halos. Which finding is most likely?

A. Owl’s-eye inclusions
B. Negri bodies
C. Guarnieri bodies
D. Cowdry type A inclusions

Which test is preferred for diagnosing HSV encephalitis?

A. Serum HSV antibody
B. CSF PCR for HSV DNA
C. Brain tissue culture
D. CSF bacterial culture

A clear zone develops within a cell monolayer after inoculation. What produced this plaque?

A. Antibodies neutralized infected cells
B. Erythrocytes covered infected cells
C. One virus killed surrounding cells
D. Two viruses blocked replication

Erythrocytes adhere to the surface of virus-infected cells. Which mechanism explains this finding?

A. Viral hemagglutinin binds erythrocytes
B. Complement lyses infected cells
C. Antibodies cross-link neighboring cells
D. Viral capsids bind leukocytes

Cytoplasmic inclusions are identified in neurons from brain tissue. Which virus is suggested by Negri bodies?

A. HSV
B. CMV
C. Poliovirus
D. Rabies virus

Which definition best describes a viral titer?

A. Lowest dilution causing cell growth
B. Highest dilution causing measurable effect
C. Average particles within each cell
D. Maximum dilution preventing infection

How are primary cell cultures produced?

A. Immortalized tumor cells are cloned
B. Embryonated eggs are enzymatically opened
C. Fresh tissue is enzymatically dissociated
D. Viruses transform mature blood cells

Trypsin or collagenase is used during culture preparation primarily to perform which function?

A. Dissociate cells from tissue
B. Destroy contaminating viral capsids
C. Prevent cellular senescence
D. Induce syncytium formation

An unknown virus prevents a known challenge virus from replicating in culture. Which phenomenon is being used for identification?

A. Heterologous interference
B. Hemadsorption
C. Plaque formation
D. Viral neutralization

Which inclusion body is associated with CMV?

A. Negri body
B. Cowdry type A inclusion
C. Owl’s-eye inclusion
D. Guarnieri body

Where can CMV owl’s-eye inclusions be identified?

A. Tissue or urine sediment
B. Blood or joint fluid
C. Sputum or cerebrospinal fluid
D. Stool or pleural fluid

Cowdry type A inclusions appear in which cells?

A. Single cells or syncytia
B. Erythrocytes or platelets
C. Neutrophils or macrophages
D. Fibroblasts or endothelial cells

Which pairing correctly matches the viral genome with its amplification method?

A. PCR—RNA; RT-PCR—DNA
B. PCR—protein; RT-PCR—antigen
C. PCR—DNA; RT-PCR—RNA
D. PCR—capsid; RT-PCR—antibody

What occurs during viral hemagglutination?

A. Released viruses clump erythrocytes
B. Antibodies lyse infected cells
C. Viruses fuse neighboring epithelial cells
D. Complement coats free viral particles

What causes hemagglutination inhibition?

A. Viral capsids destroy erythrocytes
B. Primers bind viral hemagglutinin
C. Complement blocks reverse transcription
D. Antibodies prevent erythrocyte agglutination

What is the diagnostic purpose of hemagglutination inhibition?

A. Measure patient viral load
B. Identify virus using blocking antibodies
C. Amplify viral RNA directly
D. Culture viruses in erythrocytes

Which enzyme allows RT-PCR to analyze an RNA virus?

A. DNA ligase
B. RNA polymerase
C. Reverse transcriptase
D. Restriction endonuclease

Which conversion occurs before PCR amplification during RT-PCR?

A. Viral DNA into protein
B. Viral RNA into DNA
C. Viral antigen into antibody
D. Viral capsid into RNA

Which method both identifies and quantifies viral nucleic acids?

A. Real-time PCR
B. Hemagglutination inhibition
C. Tissue culture
D. Latex agglutination

Real-time PCR can be used to analyze which viral genomes?

_____ DNA or RNA

Which method simultaneously amplifies multiple microbial genomes from one sample?

A. In situ hybridization
B. Multiplex PCR
C. Hemagglutination inhibition
D. Conventional tissue culture

Transcription-based amplification uses which combination?

A. DNA ligase and antibodies
B. Hemagglutinin and erythrocytes
C. Reverse transcriptase and specific primers
D. Collagenase and cultured cells

What product is generated from viral RNA during transcription-based amplification?

A. Complementary DNA
B. Viral messenger RNA
C. Double-stranded protein
D. Antibody-bound genome

What practical advantage distinguishes transcription-based amplification?

A. Quantifies only viral proteins
B. Requires embryonated egg culture
C. Detects only DNA viruses
D. Needs no special PCR equipment

Which infection is especially suited to detection by genome amplification?

A. Acute virus with abundant shedding
B. Easily cultured extracellular virus
C. Latent or integrated viral infection
D. Infection diagnosed by agglutination

Genome amplification is especially valuable in which situation?

A. Low-concentration viral infection
B. High-titer bacterial bloodstream infection
C. Abundant viral antigen in stool
D. Visible viral cytopathic effects

When is genome amplification particularly preferred over viral culture?

A. Readily cultured benign virus
B. Dangerous or difficult viral culture
C. High antibody titer only
D. Obvious viral exanthem

What does a patient’s viral load represent?

A. Number of infected leukocytes
B. Amount of antiviral antibody
C. Degree of tissue inflammation
D. Quantity of viral genomes present

Which method is used to measure viral load?

A. Real-time PCR
B. Latex agglutination
C. Hemadsorption
D. Conventional microscopy

In situ hybridization detects viral sequences using what?

A. Broad bacterial RNA primers
B. Fluorescent viral antibodies
C. Virus-specific DNA probes
D. Erythrocyte-bound hemagglutinin

In situ hybridization is performed on which specimen type?

A. Fresh serum samples
B. Live cell cultures
C. Unfixed urine sediment
D. Fixed tissue specimens

What can ELISA and latex agglutination detect and quantify?

A. Viral integration sites
B. Virus or released viral antigen
C. Infected-cell chromosomes
D. Host cytokine gene sequences

What is a serologic battery?

A. One viral culture repeatedly
B. Several bacterial cultures simultaneously
C. Multiple viral serologies for one syndrome
D. One antibody at serial dilutions

What material is analyzed by next-generation sequencing after viral genome amplification?

A. Viral surface antigens
B. Patient antiviral antibodies
C. Infected host proteins
D. Amplified viral DNA

How does next-generation sequencing identify an unknown virus?

A. Comparison with sequence databases
B. Detection of erythrocyte agglutination
C. Measurement of antibody titers
D. Visualization of viral plaques

Viral serology is particularly useful under which circumstances?

A. Abundant virus grows rapidly
B. Acute infection resolves immediately
C. Culture is difficult or prolonged
D. Viral proteins remain extracellular

Which infections are especially suited to serologic diagnosis?

A. Influenza, RSV, and rhinovirus
B. Rotavirus, norovirus, and astrovirus
C. Rabies, measles, and poliovirus
D. EBV, HBV, and HIV

ELISA commonly screens donated blood for which viruses?

A. HSV, VZV, and CMV
B. EBV, HPV, and rabies
C. HBV, HCV, and HIV
D. RSV, influenza, and measles

Serologic cross-reactions between related viruses may cause what?

A. False-negative cultures
B. Reduced viral shedding
C. False-positive results
D. Increased viral replication

Which are examples of solid-phase immunoassays?

A. PCR and RT-PCR
B. LA and ELISA
C. Culture and hemadsorption
D. FISH and sequencing

Indirect fluorescent antibody tests can detect and quantify what?

A. Viral antigens and antibodies
B. Only viral DNA sequences
C. Only infectious viral particles
D. Host cellular chromosomes

Solid-phase immunoassays such as ELISA can measure what?

A. Viral antigens and antiviral antibodies
B. Viral plaques and syncytia
C. Viral genomes and chromosomes
D. Cell viability and senescence

What does Western blot identify in patient serum?

A. Total viral genome quantity
B. Viral replication inside cells
C. Recognized specific viral proteins
D. Infectious virus in culture

Western blot was traditionally used for what purpose?

A. Confirming HIV infection
B. Screening influenza vaccines
C. Measuring HBV viral load
D. Detecting rabies inclusions

Immunofluorescence and EIA detect viral antigens in which locations?

A. Only extracellular body fluids
B. Only within cell nuclei
C. Only on viral envelopes
D. Cell surfaces or infected cells

Reinfection or recurrence produces which immune response?

A. Anamnestic immune response
B. Primary innate response
C. Delayed neutrophilic response
D. Absent antibody response

Which EBV antibodies are detected earliest?

A. Nuclear antigen antibodies
B. Envelope and capsid antibodies
C. Heterophile antibodies only
D. Viral polymerase antibodies

When are antibodies against EBV nuclear antigen detected?

A. Before viral exposure
B. During initial viral entry
C. During early incubation
D. During convalescence

Neutralization and hemagglutination inhibition tests detect what?

A. Viral DNA concentration
B. Infectious viral particles
C. Virus-specific antibodies
D. Infected tissue cells

How do neutralization tests detect antiviral antibodies?

A. Antibodies increase viral replication
B. Antibodies block viral activity
C. Antibodies amplify viral genomes
D. Antibodies produce viral plaques

Hemagglutination inhibition demonstrates antibodies by showing what?

A. Increased erythrocyte agglutination
B. Blocked erythrocyte agglutination
C. Destruction of infected erythrocytes
D. Viral growth within erythrocytes

During what period is virus-specific IgM usually present?

A. First two to three weeks
B. Only after several months
C. Throughout lifelong latency
D. Only during reinfection

Which finding defines seroconversion?

A. Any detectable antibody concentration
B. Loss of all viral antibodies
C. Fourfold antibody-titer increase
D. Appearance of viral antigen

Which serum specimens are compared to establish seroconversion?

A. Two acute-phase samples
B. Two convalescent-phase samples
C. Maternal and neonatal samples
D. Acute and convalescent samples

When should convalescent serum be collected?

A. Twenty-four hours later
B. Six months later
C. Two to three weeks later
D. Immediately after acute serum

A single positive viral serology generally establishes what?

A. Active viral replication
B. Exact infection date
C. Current viral shedding
D. Previous viral infection

What can routine viral serology often not determine?

A. Whether antibodies are present
B. Exact timing of infection
C. Whether serum was collected
D. Antibody assay methodology

Highly specific monoclonal antibodies may cause which result?

A. False-positive bacterial cultures
B. False-negative viral tests
C. Increased antibody titers
D. Viral genome amplification

Why may monoclonal antibodies miss a viral infection?

A. Antibodies destroy all antigens
B. Viruses prevent serum collection
C. Probes bind host chromosomes
D. Variant strains escape recognition

Which statement correctly distinguishes FISH from luminescent probes?

A. Both require actively replicating virus
B. FISH detects tissue viral sequences
C. FISH detects amplified genomes only
D. Luminescent probes examine fixed tissue

A virologist obtains cells directly from a monkey kidney for immediate culture. How is this primary culture produced?

A. Growing tumor cells continuously
B. Cloning one immortalized cell
C. Dissociating a specific animal organ
D. Infecting erythrocytes with virus

Which enzymes commonly separate tissue into cells when preparing a primary culture?

A. DNase and RNase
B. Trypsin and collagenase
C. Ligase and polymerase
D. Pepsin and amylase

A diploid cell line is composed of which cellular population?

A. Multiple changing cell populations
B. Freshly isolated organ fragments
C. One cell type
D. Erythrocytes mixed with fibroblasts

How many times can a diploid cell line generally be passaged?

A. Only one passage
B. Exactly fifty passages
C. An unlimited number
D. A large finite number

What eventually limits continued passage of diploid cell lines?

A. Immediate viral transformation
B. Senescence or characteristic changes
C. Complete chromosome loss
D. Erythrocyte contamination

Tumor and immortalized cell lines generally consist of what?

A. Several primary tissue types
B. Mixed leukocyte populations
C. Dissociated whole organs
D. A single cell type

Tumor cell lines are commonly initiated from which source?

A. Normal erythrocytes
B. Embryonated eggs
C. Bacterial colonies
D. Human or animal tumors

Immortalized lines can also be created by treating primary cells with what?

A. Oncogenic viruses or chemicals
B. Neutralizing antibodies
C. Trypsin alone
D. Erythrocytes and complement

What passage capacity characterizes immortalized cell lines?

A. One passage only
B. Continuous passage indefinitely
C. Several passages before infection
D. Passage until antibody production

Immortalized cell lines can be continuously passaged without undergoing what?

A. Viral attachment
B. Genome replication
C. Cellular senescence
D. Erythrocyte binding

What occurs during heterologous viral interference?

A. One virus blocks another virus
B. Two viruses exchange genomes
C. Antibodies agglutinate infected cells
D. One virus activates another

How can heterologous interference help detect rubella virus in culture?

A. Rubella produces visible plaques
B. Rubella agglutinates erythrocytes
C. Rubella lyses every cultured cell
D. Rubella prevents challenge-virus replication

Erythrocytes adhere directly to influenza-infected cultured cells. What is this phenomenon?

A. Hemagglutination inhibition
B. Viral neutralization
C. Heterologous interference
D. Hemadsorption

Which group contains viruses detectable through hemadsorption?

A. Influenza, parainfluenza, mumps, togavirus
B. Rotavirus, norovirus, adenovirus, astrovirus
C. HPV, CMV, EBV, parvovirus
D. Rabies, poliovirus, HIV, HBV

Why do erythrocytes adhere to certain virus-infected cells?

A. Cells secrete erythrocyte antibodies
B. Viral polymerases bind hemoglobin
C. Capsids enter erythrocyte nuclei
D. Surface viral glycoproteins bind erythrocytes

Which statement correctly describes hemagglutination inhibition?

A. Infected cells bind erythrocytes
B. Viruses destroy erythrocyte membranes
C. Antibodies block erythrocyte agglutination
D. Antibodies increase viral attachment

What does the tissue culture infectious dose (TCD) 50 measure?

A. Death in half the animals
B. Antibodies in half the patients
C. Infection in every culture
D. CPE in half the cultures

Which laboratory endpoint is measured when determining TCD50?

A. Animal mortality
B. Cytopathologic effects
C. Antibody production
D. Clinical symptoms

What does an LD50 viral titer represent?

A. Kills half the test animals
B. Infects half the cultured cells
C. Produces plaques in every culture
D. Causes antibodies in all animals

What does an ID50 viral titer represent?

A. Detectable response in half animals
B. Death in half the animals
C. Cell lysis in half cultures
D. Antibody loss in half animals

Which findings may serve as an ID50 endpoint?

A. Only animal death
B. Only antibody production
C. Only visible symptoms
D. Symptoms, antibodies, or other responses

What is the key distinction between LD50 and ID50?

A. Cell culture versus tissue staining
B. RNA viruses versus DNA viruses
C. Death versus detectable infection
D. Acute infection versus latency

Transcription-based amplification initially uses which enzyme to copy viral RNA?

A. DNA ligase
B. Reverse transcriptase
C. Restriction endonuclease
D. Viral protease

Reverse transcriptase is directed toward the desired viral sequence by what?

A. Random bacterial primers
B. Virus-specific primers
C. Antiviral antibodies
D. Erythrocyte receptors

Which regulatory sequence is attached to the newly produced cDNA (that is created by reverse transcriptase)?

A. Host ribosomal sequence
B. HSV thymidine kinase
C. T7 promoter sequence
D. HIV integration sequence

Which enzyme recognizes the attached T7 promoter?

A. T7 RNA polymerase
B. Host DNA polymerase
C. Reverse transcriptase
D. Viral protease

What does T7 RNA polymerase produce from the DNA template?

A. Viral proteins
B. RNA from DNA
C. DNA from RNA
D. Antibodies from antigens

What happens to the newly produced RNA sequences?

A. They immediately leave the reaction
B. They bind cultured erythrocytes
C. They reenter the amplification cycle
D. They inhibit reverse transcriptase

DNA probe analysis is especially useful for detecting which viruses?

A. Rapidly cytolytic viruses
B. Slowly replicating or nonproductive viruses
C. Easily cultured respiratory viruses
D. Viruses causing visible plaques

Which viruses are classic candidates for DNA probe analysis?

A. CMV and human papillomavirus
B. Influenza and parainfluenza
C. Rotavirus and norovirus
D. Rabies and poliovirus