Mycvir prelim l2

Highly stable

Temperature stability of icosahedral viruses at 37°C, losing little infectivity after several hours

Highly heat-labile

Temperature stability of enveloped viruses at 37°C, with titers rapidly dropping

50-60°C for 30 minutes

The temperature and time generally required to destroy viral infectivity

Hepatitis B virus and polyomaviruses

Two notable exceptions to the general heat inactivation of viruses at 50-60°C

Lyophilization

The freeze-drying process used to preserve viruses in a dry state at 4°C or room temperature

-20°C

The storage temperature that must be avoided because it disrupts host cells and destroys viral viability

-70°C

The optimal storage temperature for viral specimens if a processing delay of more than 4 days is anticipated

Salts

Substances added to oral polio vaccines to stabilize the virus and maintain potency for weeks at ambient tropical temperatures

5.0 to 9.0

The general pH range within which most viruses remain stable

Enteroviruses

The group of viruses known for being highly resistant to acidic pH conditions

Alkaline conditions

The pH condition under which all viruses are destroyed

Infectivity

The most radiosensitive property of a virus because replication requires expression of the entire genetic material

Ether susceptibility

The chemical reagent test used to distinguish enveloped viruses from naked (non-enveloped) viruses

Resistant

The reaction of naked DNA or RNA icosahedral viruses to ether exposure

Sensitive

The reaction of enveloped helical or icosahedral viruses to ether exposure

Nonionic detergents

Detergents (e.g., Nonidet P40 and Triton X-100) that solubilize membrane lipids and release envelope proteins in an undenatured state

Anionic detergents

Detergents (e.g., SDS) that solubilize viral envelopes and completely disrupt capsids into separated polypeptides

Formaldehyde

The chemical that destroys viral infectivity by reacting with nucleic acid while minimally affecting protein antigenicity

Single-stranded genomes

The type of viral genome that is inactivated much more readily by formaldehyde than double-stranded genomes

Photodynamic inactivation

The process where vital dyes bind to viral nucleic acids, rendering the virus susceptible to inactivation by visible light

Toluidine blue, neutral red, and proflavine

Three vital dyes frequently used in photodynamic inactivation of viruses

Antibiotics and sulfonamides

Two classes of antibacterial agents that have absolutely no effect on viruses

Quaternary ammonium and organic iodine

Two common types of disinfectants that are ineffective against viruses

Picornaviruses

The group of viruses against which alcohols (such as ethanol and isopropanol) are relatively ineffective

Steam under pressure, dry heat, ethylene oxide, radiation

Common physical and chemical methods used for viral sterilization

Sodium hypochlorite, glutaraldehyde, formaldehyde, peracetic acid

Common chemical agents used for viral surface disinfection

Chlorhexidine, 70% ethanol, iodophores

Common chemical agents used for viral skin disinfection

Dacron or rayon

The synthetic materials required for swab collection because they do not inhibit viruses or interfere with PCR

Calcium alginate

The swab material that must be avoided because it inhibits viruses and interferes with nucleic acid tests

Viral Transport Media (VTM)

A buffered protein solution with antimicrobial agents used to prevent swabs and tissues from drying out

Blood, CSF, bone marrow, urine, amniotic fluid

Clinical specimens for which Viral Transport Media (VTM) must NEVER be used

Peak viral load

The early phase of infection when the virus is actively replicating and present at its highest concentration

Cell culture

The diagnostic 'gold standard' for isolating and identifying viruses in clinical laboratories

Direct Fluorescent Antibody (DFA) test

A rapid, highly specific immunofluorescence test where labeled antibodies bind to viral antigens on a slide

Cross-reactivity

The primary limitation of the Direct Fluorescent Antibody (DFA) test when dealing with closely related viruses

Cytopathic effect (CPE)

Visible cellular morphological changes (e.g., rounding, clumping) caused by viral infection in culture

Hemadsorption

A method to detect non-CPE-producing viruses by using red blood cells that adhere to infected host cell surfaces

Centrifugation-Enhanced Shell Vial Culture

A rapid culture technique that spins samples onto cells to accelerate infection, allowing detection in 1 to 2 days

Retrospective testing

A serological approach comparing acute and convalescent antibody titers to confirm active or past viral infection

David Baltimore

The Nobel laureate who developed the virus classification system based on mRNA synthesis in 1971

Messenger RNA (mRNA) synthesis mechanisms

The core biological property used to categorize viruses in the Baltimore Classification System

Group I (dsDNA)

The Baltimore classification group containing Papillomaviridae, Herpesviridae, and Poxviridae

Group II (ssDNA)

The Baltimore classification group containing Parvoviridae (e.g., Parvovirus B19)

Group III (dsRNA)

The Baltimore classification group containing Reoviridae (e.g., Rotavirus)

Group IV (ssRNA+)

The Baltimore classification group containing Picornaviridae, Togaviridae, Flaviviridae, and Coronaviridae

Group V (ssRNA-)

The Baltimore classification group containing Orthomyxoviridae, Paramyxoviridae, Filoviridae, and Rhabdoviridae

Group VI (ssRNA-RT)

The Baltimore classification group containing Retroviridae (e.g., HIV)

Group VII (dsDNA-RT)

The Baltimore classification group containing Hepadnaviridae (e.g., Hepatitis B virus)