(exam 2) chapter 13 Viruses, Viroids, and Prions Flashcards
why do many hospital microbes become resistant?
because they have resistance factors (R factors) which encode antibiotic resistance and they are continually recombining to create new/or multiple forms of resistance
what must viruses be grown in?
living cells
what are prions?
Proteinaceous Infectious Particles; cause nine animal neurological diseases
what are plaques that the phages form?
clearings on a lawn (plate) of bacteria on the surface of agar
what are droplet precautions?
droplet nuclei from respiratory secretions (short distances)
what are the three outcomes of lysogeny?
1) immunity to infection by same phage (if it is already infected, the cell can’t get infected again)
2) may result in phage conversion— host cell exhibits new properties
3) specialized transduction ( specific bacterial genes transferred to other bacteria by phage)
what does each plaque correspond to? what are the units?
corresponds to a single virus; can be expressed as plaque-forming units (PFU)
what is a compromised host?
an individual whose resistance to infection is impaired by disease, therapy, or burns
what are universal precautions? And what are the two general category?
used to reduce transmission of microbes in healthcare and residential settings; (standard precautions and transmission-based precautions)
what is the release step in animal viruses multiplication?
by budding (enveloped viruses) or rupture
how is virus growth plotted?
logarithmically as a “one-step growth curve”
why do normal cells transform into tumor cells?
acquire properties of cancer (altered growth from normal cells; may express a tumor specific transplantation antigen on the surface and a T antigen in the nucleus)
what are bacteriophages grown in?
Bacteria
what happens in lysogenic cycle (latency)?
Phage remains more dormant; phage DNA incorporates into host cell DNA
what is the host range of a virus?
the spectrum of host cells a virus can infect; most viruses infect only specific types of cells in one host (determined by specific host attachment sites and cellular factors)
what are two main ways to become compromised?
1) broken skin or mucous membranes (burns)
2) suppressed immune system
what are transmission-based precautions?
supplemental to standard precautions; designed for highly transmissible infections and/ or dangerous pathogens
what are emerging infectious diseases (EIDs)?
diseases that are new, increasing in incidence, or showing a potential to increase in the near future
what are three reasons oncoviruses often go undetected until cancer formation?
1) most virions do not induce cancer
2) cancers may develop long after initial infection
3) cancers caused by viruses are not contagious
what is a virion?
complete, fully developed viral particle
what are taxonomy of viruses usually based off of?
typically based on their genetic info being the same and what they infect
what is the attachment step in animal viruses multiplication?
viruses attach to the cell membrane (attachment sites across virus surface bind host cell receptors)
what are contact precautions ?
contact with patient (skin, feces, vomit) or surfaces contaminated by patient
what two conditions must be met in order for a virus to multiply?
1) virus must invade a host cell
2) virus must take over the host’s metabolic machinery
what happens in the lytic cycle (lysis) ?
phage causes lysis and death of the host cell
how does one get infected by Prions?
inherited and transmissible by ingestion, transplant, and surgical instruments
what are three ways to grow animal viruses?
1) in living animals (expensive)
2) in embryonate eggs (virus injected into eggs and growth is signaled by changes or death to embryo)
3) in cell structures (most common way) tissues are infected w/ enzymes to separate cells; virally infected cells are detected via their deterioration (cytopathic effect CPE)
what are standard precautions?
applied regardless of infectious status; basic minimum practices to prevent transmission of pathogens that are applied to everyone; (include: hand washing, PPE, cleaning and disinfection practices)
what is release via rupture?
non enveloped viruses escape through holes in membrane; host cell typically dies
what is a latent infection?
virus remains in asymptomatic host cell for long periods of time (may reactivate due to changes in immunity)
what are airborne precautions?
droplet nuclei from respiratory secretions (long distances)
what are viruses?
Obligatory intracellular parasites
what is the entry step in animal viruses multiplication?
the bacteria enters by receptor-mediated endocytosis or fusion (fusion with cell membranes requires virus to be enveloped)
what are the six steps in order of animal virus multiplication?
1) Attachment
2) Entry
3) Uncoating
4) Biosynthesis
5) Maturation
6) Release
what are oncogenes?
involved in cell growth and proliferation or inhibition of apoptosis; many have been identified; activated oncogenes allows cells designated for apoptosis to survive and proliferate
in the lysogenic cycle what is the inserted phage DNA called?
a prophage
what are four specific structural components of virion? which of the four do ALL viruses contain?
ALL viruses contain the first two components
1) nucleic acid (DNA OR DNA / single stranded or double stranded / linear or circular)
2) capsid (protein coat made of capsomeres -subunits)
3) Envelope (lipid, protein, and carbohydrate coating on some viruses)
4) Spikes (projections from the outer surface)
what is release via budding?
virus acquires portion of host cell membrane; cell may live
what are bacteriophages?
‘class’ of viruses that infect bacteria
integration of oncogenic viruses can activate what?
oncogenes
what is persistent / chronic infection?
occurs gradually over a long period of time; generally fatal
what are oncogenic viruses (oncoviruses) ?
can become integrated into the host cell’s DNA and induce tumors (~ 10% if cancers are virus-induced)
what are obligatory intracellular parasites?
requires living host cells to multiply; have few to no enzymes for metabolism (No ATP generating mechanism) viruses
what is the uncoating step in animal viruses multiplication?
uncoating happens by the viral or host enzymes so the viral protein coat is separated from nucleic acid
what are the five steps of the lytic cycle in order?
1) Attachment
2) Penetration
3) Biosynthesis
4) Maturation
5) Release
what are nosocomial infections?
another name for healthcare-associated infections
what is spongiform encephalopathies?
Prion neurological disease; large vacuoles develop in the brain
what are three reasons why HAIs occur?
1) microorganisms in the hospital environment
2) weakened status of the host
3) chain of transmission in a hospital
usually is result of a combination of the three factors above
what are healthcare-associated infections (HAIs)?
infections that are acquired while receiving treatment in a healthcare facility
what are two ways of virus multiplication in bacteriophages?
1) Lytic cycle (lysis)
2) Lysogenic cycle (latency)
what are four definitive features of viruses?
1) Contain DNA or RNA; not both
2) Contain a protein coat that protects the nucleic acid
3) multiply living cells using host machinery (hinders antiviral drug development bc they use host cells)
4) produce structures to transfer viral nucleic acid to other cells
what are three main routes for chains of transmission?
1) direct contact transmission (staff to patient or patient to patient)
2) indirect contact transmission (fomites)
3) airborne transmission (ventilation system)
what is the biosynthesis step in animal viruses multiplication?
production of nucleic acids and proteins DNA Viruses (DNA replication = nucleus and protein synthesis = cytoplasm) RNA Viruses (Both RNA replication and protein synthesis = cytoplasm)
what are three types of transmission-based precautions?
1) contact precautions
2) droplet precautions
3) airborne precautions
what is the maturation step in animal viruses multiplication?
when the nucleic acid and capsid proteins assemble
