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Fundamentals of Medicine > infection and microorganisms > Flashcards

infection and microorganisms Flashcards

1
Q

name the four human pathogens

A
  • viruses
  • bacteria
  • fungi
  • parasites
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2
Q

name the two types of parasites

A
  • endoparasites

- ektoparasites

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3
Q

give examples of endoparasites

A
  • protozoa
  • parasitic worms
  • flukes
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4
Q

what size are viruses?

A

18-300 nm

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5
Q

describe the key structures of viruses

A
  • capsid (virus-encoded)

- outer cell-membrane (host derived)

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6
Q

describe viral nucleic acid

A
  • 3-300 Kb
  • DNA/RNA
  • single or double stranded
  • circular or linear
  • continuous or segmented
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7
Q

describe viral structural proteins

A
  • determine symmetry (and virus structure)
  • protect the nucleic acid
  • play a role in target cell infection
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8
Q

describe viral enzymes

A
  • often carried in virus particles to enable viral nucleic acid replication
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9
Q

describe viral glycoproteins

A
  • inserted into envelope

- play a role in host/target cell infection

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10
Q

name the three types of viral symmetry

A
  • icosahedral
  • helical
  • complex
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11
Q

give an example of an icosahedral/cubical structure

A

herpesvirus

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12
Q

give an example of a helical virus

A

influenza A

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13
Q

give an example of a complex virus

A

poxvirus

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14
Q

what determines the symmetry of a virus?

A

virus structural proteins, arranged as morphological units called capsomeres

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15
Q

how are viruses classified?

A
  • type of nucleic acid (DNA/RNA)
  • sequence of nucleic acid
  • number, ss/ds and polarity of nucleic acid strands
  • particle size, structure and symmetry
  • mode of replication
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16
Q

name the three methods of virus propagation

A
  • in vitro cell culture
  • embryonated eggs
  • animal models
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17
Q

describe in-vitro cell culture

A
  • primary cell lines

- continuous cell lines

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18
Q

describe primary cell lines

A
  • derived from healthy tissue

- finite number of cell divisions

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19
Q

describe continuous cell lines

A
  • transformed/immortalised cells

- infinite number of cell divisions

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20
Q

describe the use of embryonated eggs

A
  • amniotic fluid (influenza A)

- chorio-allantoic membranes

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21
Q

describe propagation using animal models

A

suckling mice (eg. neurotropic viruses such as poliovirus)

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22
Q

describe different methods of viral introduction to the body

A
  • oral transmission
  • droplet
  • direct inoculation
  • direct skin contact
  • trans-placental
  • sexual transmission
23
Q

describe viral entry into cells

A
  • attachment of virus to host receptor
  • penetration
  • uncoating (capsid is shed)
  • replication
  • assembly (capsids form around nucleic acid)
  • release (by budding forming envelope/exocytosis)
24
Q

how does a virus penetrate a host cell?

A
  • receptor-mediated endocytosis

- fusion

25
Q

how does a virus leave the host?

A
  • budding to form envelope

- exocytosis if no envelope present

26
Q

describe viral replication

A
  • synthesis of viral mRNA
  • synthesis of viral protein for new capsids
  • synthesis of viral nucleic acid
27
Q

how is ss retro RNA transcribed

A

RNA –> DNA/RNA (ds) –> transcription

28
Q

what are the early viral proteins used for?

A
  • non-structural proteins

- enzymes, regulatory molecules for replication

29
Q

what are the late proteins used for?

A
  • structural proteins

- formation of capsid

30
Q

how is ss- replication different from ss +?

A

need to first produce + strand of RNA

31
Q

how is viral replication different between RNA/DNA?

A
  • DNA viruses replicate their genome in the NUCLEUS

- RNA viruses replicate their genome in the CYTOSOL

32
Q

describe budding of viruses

A
  • glycoproteins synthesised by mRNA and inserted into the host plasma membrane
  • matrix proteins are synthesised by viral mRNA. They form part of the envelope
  • modified region extends off and is budded from the plasma membrane
  • modified region encloses the viral matrix protein and RNA within the capsid
33
Q

describe egress by cytolysis

A

cell destruction

causes a cytopathic effect (CPE)

34
Q

name a function of CPE

A

diagnostic virology (virus detection in tisse culture)

35
Q

give the outcomes of viral infection

A
  • acute lytic infection
  • persistent infection with shedding
  • latent infection with reactivation
  • persistent slow infection with or without acute stage
  • transformation
36
Q

what is an acute lytic infection?

A
  • virus replication and release of virus progeny via cell lysis
37
Q

give examples of acute lytic infections

A

poliovirus

influenza A

38
Q

describe ‘persistent infection with shedding’

A

virus persists in cell and replicates slowly

39
Q

give examples of ‘persistent infection with shedding’

A

hep B

40
Q

describe ‘latent infection with reactivation’

A
  • virus persists in cell but is quiescent
  • disruption of latency triggers reactivation
  • genetic material may persist in host cell nucleus
41
Q

give an example of ‘latent infection with reactivation’

A

herpes

42
Q

what is an episome?

A

genetic material remains in host cell nucleus

43
Q

describe ‘persistent slow infection with/without acute stage’

A

genetic material may integrate into host cell genome

44
Q

give an example of a ‘persistent slow infection’

A

HIV

45
Q

describe ‘transformation’

A

disruption of normal growth processes

46
Q

give examples of normal growth provesses

A

EBV, HPV

47
Q

how do transformed cells differ from healthy cells?

A

(in vitro)

  • greater saturation density
  • higher growth rate
  • loss of contact inhibition
  • appearance of ‘new’ cell surface antigens
  • indefinite growth
48
Q

size of poliovirus

A

30nm

49
Q

describe poliovirus structure

A
  • ss + strand
  • non-enveloped
  • icosahedron
  • made up of 4 capsid proteins
50
Q

describe the action of poliovirus

A
  • replicates in cytoplasm
  • cytopathic (causes lysis)
  • infects gut and replicates in GALT
  • can infect and destroy motor neurones
51
Q

describe the consequences of poliovirus

A
  • asymptomatic mild infections in 99% of cases
  • meningitis
  • paralytic poliomyelitis (1:1000 of poliovirus infections in children)
52
Q

herpes virus size

A

150 nm

53
Q

herpes virus structure

A
  • enveloped
  • icosahedron
  • 162 capsomeres
54
Q

describe the action of herpes

A
  • replicates in nucleus
  • cytopathic
  • infects epithelium, enters and ascends axons
  • establishes latent infection in neural ganglia
  • reactivation causes descent along same axons and replication in epithelium

Fundamentals of Medicine (1 decks)

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