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principles of disease > medical microbiology week 5 > Flashcards

medical microbiology week 5 Flashcards

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1
Q

what are some microbial causes of infection

A
  1. bacteria (prokaryotic)
  2. viruses (unclassified)
  3. fungi (eukaryotic)
  4. parasites (usually eukaryotic)
  5. prions (unclassified)
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2
Q

what is a prion

A

protein of unknown function that resides on the surface of brain cells

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3
Q

what’s bigger a prion or a virus

A

virus

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4
Q

what’s bigger a bacteria or a virus

A

bacteria

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5
Q

what’s bigger a fungi or a bacteria

A

fungi

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6
Q

in microscopy when would you not use a stain

A
  • to see white blood cells (e.g. urine)

- to see parasites (e.g. faeces)

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7
Q

in microscopy when would you use a stain

A

to visualise bacteria and yeasts/fungi

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8
Q

can you see viruses in light microscope

A

no

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9
Q

how do you detect viruses in clinical samples

A 
molecular methods
- real time/PCR
- antigen detection
- serology to determine immunity 
virtually obsolete methods 
- electron microscopy
- cell or tissue culture
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10
Q

how is parasite diagnosed

A
  • microscopy of different life cycle stages
  • culture rarely possible
  • serology sometimes useful
  • reference laboratories
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11
Q

what characteristics do bacterial cells have

A
  • capsule
  • cell wall
  • single chromosome
  • no nucleus
  • flagellum
  • fimbriae
  • ribosomes
  • plasma membrane
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12
Q

what is the outer membrane on a bacterial cell

A

component of the gram negative cell wall

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13
Q

is a gram positive cell wall thin or thick

A

thick

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14
Q

is a gram negative cell wall thin or thick

A

thin

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15
Q

what does a gram positive cell wall contain

A
  • plasma membrane with proteins
  • then periplasmic space
  • then peptidoglycan
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16
Q

what does a gram negative cell wall contain

A
  • plasma membrane with proteins
  • then periplasmic space
  • then peptidoglycan
  • then outer membrane (which contains lipopolysaccharides and proteins)
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17
Q

what is gram stain colour of gram positive in light microscopy

A

purple

- think Purple for Positive

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18
Q

what is gram stain colour of gram negative in light microscopy

A

red

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19
Q

what shape is cocci

A

spherical

- cOcci like sphere

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20
Q

what shape is bacilli

A

rod shaped

- think bacilli = baton

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21
Q

where are lipopolysaccharides present

A

in outer membrane of gram negative bacteria

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22
Q

what is fimbriae on bacteria there for

A

adherence

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23
Q

what do lipopolysaccharides do

A
  • protects peptidoglycan from bile salts
  • blocks many antibiotics from getting into cell
  • lipid A within LPS forms endotoxin which when in bloodstream may give rise to endotoxic shock (fever and low BP)
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24
Q

how do bacteria replicate

A
  • binary fission
  • asexual
  • genetic material duplicates then cell divides into two
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25
how does genetic variation in bacterial cell occur
- spontaneous mutation - transfer of plasmids between bacteria - conjugation is mechanism of gene transfer
26
how do you detect individual bacteria
- can only be seen with microscope using stain (e.g. gram, fluorescent dyes)
27
how do you detect colonies of bacteria
- cultured on solid medium (agar) | - can be seen with eye
28
what is a parasite
an organism that lives in or on another organism (host) and derives its nutrients at the expense of this host
29
what is a vector
- intermediate host | - transmitis parasite
30
what are protozoa
basically single celled organisms that can live both within the environment and the host e.g. malaria, amoebae, flagellates
31
how are protozoa transmitted
protozoa that live in human's intestine - faecal-oral route (amoebae) protozoa that live in the blood or tissue of humans - insect vector
32
what is the malaria parasite called
plasmodium
33
what are helminth parasites
worms
34
what are nematodes
``` round worms (helminth) ```
35
what are cestodes
tapeworms | helminth
36
what are trematodes
flatworms/fluke | helminth
37
what is enterobiasis
thread worm (nematode - helminth)
38
what is amoebic dysentry
protozoa parasite
39
what is route of transmission for nematodes
faecal-oral route
40
what is ascaris lumbricoides
nematode (helminth)
41
what is the definitive host for tapeworms
humans
42
what is the route of transmission for tapeworms
eating raw/undercooked meat
43
where in the body can flatworms cause infection
blood, lung, liver, pancreas, intestines
44
what is schistosomiasis
trematode (helminth)
45
what is the route of transmission for schistosomiasis
contact with fresh water where the snail (intermediate host) is present
46
how to identify parasitic infection
- blood microscopy e.g. malaria | - stool microscopy for enteric pathogens
47
how to identify helminth infection
usually accompanied by eosinophilia and elevated IgE
48
what does a fungus form
spores
49
does a fungus have a cells wall
yes | - contains polysaccharide and it absorbs nutrients
50
what are the three groups of fungi
basidiomycetes (e.g. mushrooms) ascomycetes (e.g. neurospora) zygomycetes (e.g. bread moulds)
51
what is a dermatophyte's main virulence factor
enzymes degrade and use keratin as a nutrient source
52
what diseases are caused by dermatophytes
'ringworm' infections | - name usually starts with tinea...
53
what are the main causative agents of dermatophytosis (fungal)
- epidermophyton - microsporum - trichophyton
54
what host factors contribute to pathogenicity of fungal infection
- favourable micro-environments (warm, moist) encourage growth on skin and mucous membranes - broad-spectrum antibacterial agents reduce competition for colonisation sites in gut - immunosuppression may create a window of opportunity for fungal invasion
55
what can cause immunosuppression of host defences
iatrogenic - steroids, chemotherapy, organ transplant | disease processes - AIDS, leukaemia, endocrinopathies
56
what is yeast
fungus
57
what is candida spp.
yeasts
58
what does candida auris (fungus) cause
UTI | urinary tract infections
59
what dos candida glabrata cause
skin infections
60
what are the diagnostic methods for fungus
direct detection - histopathology, high-res CT scan detection of circulating fungal antigens detection of circulating anitbodies to fungi PCR for fungal DNA culture of fungus from normally sterile site MALDI-ToF biotyping
61
what are problems with anti-fungal drugs
- some have narrow spectrum of activity - might be static (prevents multiplying) rather than cidal (kills) - IV vs. oral - toxicity - resistance - expensive
62
what are some antifungals
echinocandins - target wall triazoles and allylamines - target sterols polyenes - target membrane flucytosine - targets DNA synthesis
63
what are the3 | different types of structures of viruses
icosahedral - 20 faces, each an equilateral triangle helical - protein binds around DNA/RNA in helical fashion complex - neither icosahedral or helical
64
where can viruses replicate
can only replicate within host
65
what is a virion
- extracellular form of virus | - exists outside host and facilitates transmission
66
what is the structure of a virion
- lipid envelope - protein capsid - virion associated polymerase - spike projections - nucleic acid
67
how do viruses replicate
1. attachment to cell 2. uncoating of lipid envelope 3. replication of nucleic acid (in nucleus mRNA synthesis) 4. protein synthesis 5. vision assembly 6. budding and release 7. maturation
68
what are the 3 possible outcomes of viral infection
- clearance of virus (with short, long term or no immunity) e.g. measles - chronic infection e.g. HIV, hep B latent infection e.g. herpes - transformation (long term infection with altered cellular gene expression) e.g. HPV
69
what is viral latency
- after infection virus lays dormant - full genome retained in host cell but no expression, so few viral antigens and no viral particles produced - reactivation can occur
70
viruses and cancer examples
EBV: Hodgkin's lymphoma human herpes 8: primary effusion lymphoma human T cell lymphotropic virus (HTLV) leukaemia HPV: cervical, anal cancers hep B/C: hepatocellular carcinoma
71
what are the viral detection methods for the whole organism
- microscopy | - culture
72
what would be the viral detection methods for part of the organism
- antigen detection - DNA/RNA detection (extraction of genetic material from sample) - PCR
73
what would be the viral detection methods for immune response
- antibody detection (serology)
74
are antiviral therapies virustatic or virucidal
all are virustatic
75
what are antiviral therapies used for
prophylaxis - to prevent infection pre-emptive therapy - when evidence of infection/replication detected but before symptoms are apparent overt disease suppressive therapy - to keep replication low
76
viruses with what properties can be eradicated
- no animal reservoir or ability to amplify in environment - clearly identifiable - no chronic carrier state - efficient and practical intervention e.g. vaccine - political/social support e. g. measles, polio
77
what are some signs of clinical infection
inflammation, pain, pyrexia (fever), tachycardia (fast heart rate), rigors (temperature rises and shivers), increased white cell count, increased reactive protein (CRP)
78
what is a commensal
an organism which is part of normal flora
79
what is infectivity
ability to become established on or within a host
80
what are exotoxins
released extracellularly by the micro-organism
81
what are enterotoxins
exotoxins which act on the GI tract
82
what are endotoxins
structurally part of the gram negative cell wall
83
what are superantigens
certain exotoxins of strep progenies and staph aureus - able to stimulate division of T cells in the absence of specific antigen - overwhelming cytokine production causes 'toxic shock'

principles of disease (19 decks)

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