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Animal Health & Disease > Lecture #2: Bacteria & Viruses > Flashcards

Lecture #2: Bacteria & Viruses Flashcards

1
Q

what is pathogenesis?

A

the explanation of how and why a disease develop

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2
Q

what are some components of microbial pathogenesis?

A
  • exposure
  • entry
  • local replication and spread
  • damage to the host
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3
Q

how can microbial pathogenesis cause damage to the host?

A
  • direct damage
  • release of toxins and/or irritant enzymes/proteins
  • induction of host immune response (innate or adaptive)
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4
Q

what is the mechanism for direct damage by micro-organisms to cell and tissues?

A
  • production of toxins
  • production of enzymes
  • apoptosis
  • virus-induced cytopathic effects: cell lysis
  • inclusion bodies: intracytoplasmic or nuclear -transformation
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5
Q

what is the mechanism for damage via the host immune response?

A
  • cytotoxic T cells and natural killer lymphocytes
  • autoimmunity
  • immediate hypersensitivity (allergy)
  • cytotoxic hypersensitivity
  • delayed type hypersensitivity
  • immune complexes
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6
Q

what are the main causes of disease?

A
  • prions
  • virus
  • bacteria
  • fungi
  • protozoa
  • toxins
  • genetic conditions
  • physical agents
  • metabolic alterations
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7
Q

what are prions?

A
  • “proteinaceous infectious particle”
  • simple proteins smaller than viruses
  • lack a genome
  • resistant to heat and chemical agents
  • form of protein naturally occurring in mammals but their exact purpose remain uncertain (neuronal?)
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8
Q

what is TSE ? when does it occur?

A

TSE =transmissible spongiform encephalopathy, occurs when non-pathogenic prions are converted into pathogenic forms (resistant to proteases)

pathogenic prions from contaminated food and normal prions interact and transform them into lethal agents

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9
Q

what is the fundamental event in prion disease pathogenesis?

A

the conformational conversion of the prion protein (PrP) from its normal or cellular form (PrPc) into a disease causing form (PrPsc). Once formed PrPsc replicates by inducing the conversion of PrPc into addational PrPsc molecules

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10
Q

what are some neuropathological features of prion disease?

A

formation of vacuoles (unstained) and PrP deposits (dark brown)

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11
Q

what are the two types of macromolecules that viruses contain?

A

nucleic acid and protein (they contain only one species of nucleic acid, either DNA or RNA)

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12
Q

what is an important difference between bacteria and viruses?

A

bacteria contain both species of nucleic acids (DNA and RNA) whereas viruses contain only one (DNA or RNA not both)

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13
Q

what are some important features of viruses?

A
  • attach to host cell with a specific receptor binding protein
  • cannot replicate autonomously (obligate intracellular parasites)
  • viruses “hijack” cellular machinery towards the production of new viral particles
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14
Q

what are 5 important structural features of viruses?

A
  1. Virion: an individual virus particle
  2. Nucleocapside: protein coat+ genome
  3. Capside: a nucleocapsid without a genome
  4. Capsomeres: protein subunits
  5. Envelope: viral glycoproteins and a lipid bilayer from host cells
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15
Q

what are some classification criteria for viruses?

A
  • the nucleic acid genome (DNA or RNA)
  • the presence or absence of envelope
  • the shape of the capsid (icosahedral, helical or complex)
  • mode of replication
  • cell tropism (preferred cell type for replication)
  • type of pathology
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16
Q

what is meant by Icosahedral symmetry? give an example of a virus that has this symmetry.

A

the capsid consists of 20 triangular facets and 12 corners or apices. ex: Adenovirus

17
Q

what is meant by helical symmetry?

A

nucleocapsid proteins are arranged like the steps of a spiral staircase forming long cylinders. Ex: Influenzavirus

18
Q

what do structural virion proteins do?

A
  • attach to receptors on cells
  • protect nucleic acid
  • penetrate cell membrane
  • replicate nucleic acid (some viruses)
  • modify host cell (some viruses)
19
Q

what do non-structural virion proteins do?

A
  • enzymes needed for DNA replication
  • proteins that affect cell physiology
  • proteins that suppress the host cell’s defenses
20
Q

what are the two phases of viral infection and what happens in them?

A
  1. the early phase: virus establishes proper cell environment required for viral genome replication and the viral DNA or RNA polymerase is produced
  2. Late phase: viral genome is amplified and structural components of the virion accumulate. at this point a considerable part of the cellular metabolism is committed to viral reproduction
21
Q

what is a latent injury?

A
  • reactivation of viral infection at a later time
  • transformation and proliferation resulting in neoplasias
22
Q

what are some determinants of viral tissue tropism?

A
  • host cell receptors for the virus
  • cellular transcription factors that recognize viral enhancer and promoter sequences
  • anatomic barriers
  • local temperature, pH and host defenses
23
Q

what are some characteristics of bacteria?

A
  • have a single chromosome consisting of circular double stranded DNA coiled in a nucleoid
  • have plasmids (DNA that replicate independently of the nucleoid)
  • some produce spores in unlivable conditions
24
Q

why are plasmids important?

A

important for antibiotic resistance and can encode virulence factors

25
Q

what are used to identify bacteria?

A
  • shape: Cocci, Bacilli, Spirochetes , etc
  • cell wall characteristics (Gram -ve=red vs. gram +ve= blue or purple)
  • biochemical rxns
  • form of respiration: aerobic or anaerobic
  • genetic homology (16S rRNA, DNA sequencing)
26
Q

what is the difference between a Gram +ve cell wall and a Grame -ve cell wall?

A

Gram -ve: inner membrane+ small peptidoglycan layer + outter membrane + lipopolysaccharide layer

Gram +ve: inner membrane + thick layer of peptidoglycan + capsule

27
Q

what are some main bacterial shapes?

A
  • Coccus= sphere
  • Baccilli= Rod
  • Spirochete= spiraled
  • Spirillum = curved
  • filamentous= filament or string like
28
Q

Transcription and translation are coupled in bacteria. the bacterial protein synthesis machinery is an important target for ______.

A

antibiotics

29
Q

what are some adhesins for bacteria?

A
  • capsular material
  • proteins
  • fimbriae + pili
30
Q

what are virulence factors for bacteria?

A
  • endotoxins & exotoxins
  • enzymes (proteases, coagulases, fibrinolysis)
  • ability to survive and proliferate intracellularly
31
Q

how is bacteria spread in the host?

A
  • bloodstream and lymphatics
  • macrophages may aid in spread
  • exotoxins may help digest tissue away
32
Q

what is chemotaxis?

A

movement of a motile cell or organism, or part of one, in a direction corresponding to a gradient of increasing or decreasing concentration of a particular substance

Animal Health & Disease (7 decks)

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