Microbiology Flashcards
1
Q
what is a virion?
A
an infectious virus particle
2
Q
what is a protomer?
A
identical protein subunit making up the capsid
3
Q
what shapes can a capsid be?
A
icosahedral, helical or complex
4
Q
name 4 viruses of icosahedral symmetry
A
adenovirus, papillomavirus, parvovirus, herpesvirus
5
Q
name 2 viruses of helical symmetry
A
rhabdovirus, parainfluenza virus
6
Q
name a virus of complex symmetry
A
poxvirus
7
Q
name a non-enveloped DNA virus
A
canine parvovirus
8
Q
name an enveloped DNA virus
A
feline herpesvirus
9
Q
name a non enveloped RNA virus
A
foot & mouth disease virus
10
Q
name an enveloped RNA virus
A
influenza virus
11
Q
t/f
viral genome can be both DNA or RNA
A
false. can only be one or the other
12
Q
where do DNA viruses replicate?
A
most in nucleus
13
Q
where do RNA viruses replicate
A
most in cytoplasm
14
Q
are DNA or RNA viruses more prone to mutation?
A
RNA viruses
15
Q
are DNA or RNA viruses stable?
A
DNA viruses
16
Q
t/f
envelopes derived from viral cell?
A
false. derived from host cell
17
Q
are enveloped or non-enveloped viruses stable?
A
non-enveloped
18
Q
t/f
enveloped viruses usually easily inactivated by disinfectants
A
true
19
Q
what is mutation?
A
structural alteration in nucleic acid
20
Q
mutation has important effects on…
A
- virulence of virus
- host range of virus
21
Q
point mutation
A
single nucleotide substitutions
22
Q
viral recombination
A
exchange or transfer of genetic material between diff but closely related viruses infecting same cell
23
Q
antigenic DRIFT
A
gradual accumulation of point mutations (common)
24
Q
antigenic SHIFT
A
acquisition of new gene from another virus due to recombination or reassortment (rare)
25
In influenza virus, what allows it to attach and to where?
Hemagglutinin, attaches to respiratory epithelium
26
when did the spanish influenza arise?
1918
27
spanish influenza aka...
H1N1 virus
28
how was H1N1 passed to humans
bird-to-human transmission
29
what are the types of virus-cell interactions?
- Lytic infection
| - Persistent infection
30
What are types of persistent infection?
- productive
- latent
- non-productive transforming
31
example of lytic infections
- canine parvovirus
| - foot and mouth disease virus
32
examples of persistent productive infections
- rabies
| - foot and mouth disease
33
examples of persistent latent infections
- herpes virus
| - retrovirus
34
example of non-productive transforming infections
equine sarcoids
35
types of viral effect on cell morphology
- cytopathic
- inclusion bodies
- alterations in cell membrane
- formation of syncytia
- haemadosorption
36
describe cytopathic effect
- seen in vitro
- seen in cell monocultures infected with virus
- nature of CPE can be diagnostic
37
describe inclusion bodies
morphological changes seen in cells infected with certain viruses
38
all viral infections produce inclusion bodies. t/f?
false.
39
give some examples of inclusion bodies
- masses of viral nucleocapsids (e.g. rabies)
- masses of viral proteins and nucleic acid (e.g. pox)
- crystalline aggregates of virions
- degenerate nuclear DNA (e.g. herpes)
40
give examples of alterations to cell membranes
- increase in permeability
- altered ion exchange/membrane potential
- proliferation/rearrangement of membrane
- insertion of viral glycoproteins
41
what is syncytia?
viral proteins inserted into plasma membrane of cell may lead to fusion of between neighbouring cells (e.g. herpes, coronavirus)
42
what is haemadosorption?
adherence of RBCs to other cells or particles
43
name ways viruses damage cells
- cell lysis
- inhibit acid synthesis
- inhibit protein synthesis
- cytopathic effects
- cytolysis
44
how can viral interference occur?
- superinfection exclusion
| - interferon mediated interference
45
what are cytokines that are produced rapidly (but transiently) in response to viral infection?
interferons
46
what is the paracrine effect?
interferons released by infected cell and binding to receptors on neighbouring cells
47
what are some routes of viral entry?
- respiratory system
- alimentary system
- skin
- urogenital tract
- conjunctiva
48
what is the most common route of viral entry
respiratory system
49
how do particles enter respiratory system?
impaction - large - nasopharynx
sedimentation - medium - small airways
diffusion - small - alveoli
50
where are sites of defence in respiratory system?
- nasal passages
- nasopharynx
- larynx
- lower respiratory tract
51
where are cough receptors located?
larynx
52
where is the mucociliary escalator?
lower respiratory tract
53
where are turbinate bones?
nasal passages
54
where are lymphoid nodules in submucosa?
nasopharynx
55
what is the 2nd most common route of viral entry?
alimentary system
56
what are some defences of the alimentary system?
perstalsis, mucous, bile, proteases, gastric acid, secretory IgA, tight junctions, lymphoid tissue (peyers patches), constant cell turnover
57
what are some barrier disruptions to skin defences?
- cuts, abrasions, trauma
- biting arthropods
- animal bites
- latrogenic
58
where would defence mechanisms of tear production and mechanical 'wiping' occur?
conjunctiva
59
what are some defence mechanisms of the urogenital tract?
- urinary flushing
- anatomical barriers
- low pH
- secretory IgA
60
how can viruses spread from site on entry?
- apical release
| - basolateral release
61
what type of directional spreading moves to contagious surfaces?
apical release
62
what is basolateral release?
directional shedding favouring internal dissemination
63
once in sub-epithelial tissues, virus disseminates via...
- lymphatics
- bloodstream
- nerves
64
in haematogenous spread, how can virions be transported through the blood?
- free virions in plasma
| - absorbed to, or within blood cells
65
what is neural spread?
viral spread through peripheral nerves
66
retrograde (centripetal) transport
allows access to CNS
67
anterograde (centrifugal) transport
allows access to peripheral tissue
68
what is viraemia?
presence of infectious virus in the blood
69
what are the 3 requirements for successful infection?
- sufficient viral particles present at site of infection
- cells at site of infection susceptible and permissible
- host defences inactive or absent
70
how do dogs get distemper?
- transmission from recently infected animal or fresh formites
- virus enters host via aerosol droplets that contact upper respiratory tract epithelium
- viral replication within 24hrs in local tissue macrophages then spreads via these cells to local lymphoid tissue
- widespread viraemia and viral proliferation within lymphoid, acute fever and leukopaenia
- viral invasion of epithelial tissue and CNS depending on dogs humoral & cell mediated immunity and viral virulence
71
what is viral tropism?
ability of virus to selectively infect particular cell types
72
what is enterotropic?
virus replicates in cells of GIT
73
what is it called when virus replicates in cells of nervous system?
neurotropic
74
what are determinants of tissue tropism?
- accessibility
- susceptibility
- permissiveness
- immune response
75
viruses passed in faeces generally more resistant to environmental inactivation. true/false?
true
76
what are some possible outcomes of foetal infection?
- abortion/stillbirth
- foetal malformation
- foetal tolerance
- recovery with no adverse effects
77
with BVDV, what happens if infection occurs 80-125 days?
- defects in brain and eye tissues
- surviving calves remain infected for life
- become immune tolerant of virus
- later die of mucosal disease from viral mutation
78
with BVDV, when would foetal death and resorption occur?
<80days gestation
79
with BVDV, what is the 125 day gestation threshold significance?
immune system fully developed in foetus by 125 days
80
what are patterns of infection a result of?
interplay between characteristics of viral lifecycle and host immune response
81
acute infection is...
brief, self-limiting infection
82
chronic infection is...
long-lasting, from months to life
83
latent infection is...
resting/hiding, viral recrudescence
84
slow infection is...
maybe long preclinical phase, can infect others in this time
85
what viruses cause epithelial damage leading to secondary bacterial infections?
- canine parvovirus - septicemia
| - foot & mouth - bacterial infection
86
what viruses cause immune damage leading to secondary infection?
- FIV - infecting lymphocytes and monocytes - reduced cell mediated immunity
- measles cause immunosuppression
87
what is immunopathology
damage caused by host immune response
88
what is a result of immunopathology?
hypersensitivity reactions
89
what is an example of a virus that causes immunopatholgy?
feline infectious peritonitis (FIP)
90
what happens when immune system recognises host proteins as foreign?
autoimmune disease
91
what can cause autoimmune disease?
- molecular mimicry
- revealing previously hidden antigens
- incorporation of host proteins in virions
- persistent infection
92
what is viral oncogenesis?
viral infection leading to tumour production
