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Z Old Infection IGNORE > Microbial Virulence > Flashcards

Microbial Virulence Flashcards

1
Q

What are ‘indigenous biota’?

A

Micro-organisms that lie on our body surfaces, both internal and external, and are mainly bacteria

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2
Q

What are indigenous biota constantly in?

A

Dynamic reflux

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3
Q

What do normal clearing systems provide?

A

A semi-sterile environment in the upper GI tract and lower respiratory tract

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4
Q

What is the importance of the bodys clearing system?

A

Although normal microbiota have low pathogenic potential, any change can lead to mild to life threatening endogenous infection

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5
Q

What is the principle reserve for our microbiota?

A

The GI tract

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6
Q

What may breaches of the GI tract lead to?

A

Heavy soiling of normally sterile sites

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7
Q

What does virulence refer to?

A

The relative capacity of a microbe to cause damage to a host

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8
Q

What can the concept of virulence occupy?

A

The full spectrum of non-pathogenic to highly pathogenic, which can result in life-threatening conditions

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9
Q

Is there variety in virulence between strains of pathogens?

A

Yes

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10
Q

What causes variety in virulence between strains of pathogens?

A

Changes in virulence factor repertoire and mobile genomic content

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11
Q

Give an example of a pathogen that has variety in virulence between its strains?

A

S Aureus

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12
Q

What is a pathogen defined as?

A

A microbe capable of causing host cell damage

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13
Q

What can pathogens be categorised into?

A
  • Obligate pathogen
  • Typical pathogen
  • Opportunistic pathogen
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14
Q

Where are obligate pathogens found?

A

Only in humans associated with disease

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15
Q

Give an example of an obligate pathogen

A

Mycobacterium tuberculosis

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16
Q

What is meant by a typical pathogen?

A

Can be present as part of the normal biota, yet frequently cause disease

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17
Q

Give an example of a typical pathogen

A

H. Influenzae

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18
Q

Where is an opportunistic pathogen seen?

A

Only in immunocompromised patients, breaches of normal defences, or congential defects

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19
Q

Give an example of an opportunistic pathogen?

A

S. Epidermidis

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20
Q

What are the two main ways in which an individual will encounter a pathogen?

A
  • Endogenous
  • Exogenous
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21
Q

What happens in endogenous infections?

A

The normal microbiota can multiply and develop

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22
Q

What are endogenous infections due to?

A

Disruption of normal defences

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23
Q

What happens in exogenous infections?

A

Infecting bacteria have been acquired from an external source, and is not part of the natural microbiota

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24
Q

Where can pathogens come from?

A
  • Food
  • Water
  • Aerosols
  • Blood
  • Bodily fluid
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25
Q

What does the natural surface defence mechanism provide?

A

A formidable barrier

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26
Q

What can a break in the natural surface defence mechanism cause?

A

Pathogenic infection

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27
Q

What are the main points of entry for bacteria?

A
  • Ingestion
  • Inhalation
  • Sexual transmission
  • Vertical transmission
  • Vectors
  • Trauma
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28
Q

How can many pathogens cause disease?

A

Through toxin-mediated release

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29
Q

What do some pathogens require to cause disease?

A

Colonisation of the host

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30
Q

What does colonisation of the host require?

A
  • Resistance to the flushing mechanism
  • Compete with the normal microbiota for colonisation of the mucosa
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31
Q

Give an example of a flushing mechanism of the body?

A

The muco-ciliary escalator

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32
Q

What features might a pathogen have to help them successfully colonise a host?

A
  • Pili
  • Fimbriae
  • Flagella
33
Q

What is the purpose of pili and fimbriae?

A

Bind to host cell

34
Q

What are flagella used for?

A

Aid bacterial mobility

35
Q

What are flagella vital for?

A

The early phase of infection, especially in the GI tract

36
Q

By what mechanisms can bacterial cells gain access to the host cell?

A
  • Simple endocytosis
  • Using molecular syringe to secrete effector proteins into the cell to allow for its uptake
  • Degrading enzymes for connective tissue or neighbouring cells can be released, and the bacterial cells can stay in the tissue and multiply
37
Q

What happens once bacterial cells have gained access to the host cell?

A

Toxins can be released, or there is potential for spread of the organisms into the bloodstream to cause pathogenic effects systemically

38
Q

How can bacteria cause pathogenic effects systemically?

A

Bacteria can stay in the tissue and release toxins into the bloodstream

39
Q

How can bacteria cause damage?

A
  • Wide range of degrading enzymes
  • Secrete cytolysins
40
Q

What degrading enzymes can be secreted by bacteria?

A
  • Proteases
  • DNAases
  • Collagenases
  • Lipases
41
Q

What is the effect of degrading enzymes secreted by bateria?

A

They cause tissue damage

42
Q

What do cytolysins do?

A

Damage the cytoplasmic membrane of the host cells, and cause cell death

43
Q

What are toxins?

A

Bacterial products that harm tissues or affect key biological events at local or distant sites, working in small concentrations

44
Q

What are the main types of toxins?

A
  • Endotoxins
  • Exotoxins
  • Superantigens
45
Q

What are endotoxins also known as?

A

Lipopolysaccharides

46
Q

Where are endotoxins found?

A

In the outer membrane of Gram negative bacteria

47
Q

When can endotoxins be present in high levels?

A

During infection

48
Q

What do endotoxins do?

A

Promote inflammatory responses in individuals

49
Q

What is the result of the endotoxin promoted inflammatory response?

A
  • Fever
  • Vasodilation
50
Q

What can endotoxins promote in very high concentrations?

A

Systemic inflammatory response syndrome (SIRS)

51
Q

What can endotoxins produce if left untreated?

A
  • Septic shock
  • Fever
  • DIC
  • Multi-organ failure
52
Q

What are exotoxins?

A

Proteins produced by bacteria that disrupt the function or kill target cells

53
Q

How can exotoxins spread?

A

Systemically, even if the bacteria producing them is only locally located

54
Q

How do superantigens exert their effects?

A

By binding to T cell receptors and MHC class II, and mimicking the effects of antigen presentation

55
Q

What do the effects of superantigens produce?

A

An inflammatory response with SIRS like pathology

56
Q

What is a good example of a toxin mediated reponse?

A

The cholera toxin

57
Q

What is the cholera toxin composed of?

A

An A and 5 B subunits

58
Q

What do the B subunits of the cholera toxin do?

A

Activates GM1-ganglioside receptor on the intestinal cell

59
Q

What does the activation of the GM1-ganglioside receptor on the intestinal cell wall allow?

A

Endocytosis of the toxin

60
Q

What happens when the cholera toxin has been endocytosed?

A

It is cleaved

61
Q

What does the A subunit of the cholera toxin do?

A

Activate adenylyl cylase

62
Q

What is the result of the cholera toxin activating adenylyl cylase?

A

It causes an increase in cAMP, which stimulates the efflux of ions and thus the efflux of water

63
Q

What is the result of the efflux of water caused by the cholera toxin?

A
  • Severe dehydration
  • Electrolyte imbalance
64
Q

What can the inflammatory response to a virus do?

A

Produce collateral tissue damage

65
Q

What is the collateral tissue damage caused by the inflammatory response to viruses mediated by?

A
  • Neutrophils
  • Macrophages
  • Complement
66
Q

What can result from swelling caused by viruses?

A

Compromised tissue perfusion

67
Q

Why can viruses lead to an autoimmune response?

A

Due to mimicy of pathogen and tissue

68
Q

Give an example of where a virus leads to an autoimmune response

A

Rheumatic fever with S. Pyogenes

69
Q

How do viruses cause pathology?

A
  • Direct viral cytopathogenesis
  • Viral immunopathogenesis
70
Q

What do viruses cause in direct viral cytopathogenesis?

A
  • DNA damage
  • Alteration of the membrane structure
  • Direct cellular cytotoxicity of cellular components
71
Q

What develops from viral immunopathogenesis?

A
  • Flu-like symptoms
  • Delayed hypersensitivity responses
  • Immune complex diseases develop
72
Q

What is the outcome of an infection dependent on?

A
  • The virulence of the infecting pathogen
  • Age
  • Nutritional status
  • General health
  • Vaccination history
  • Genetic background
  • Site of infection
  • Number of invading pathogens
73
Q

By what mechanisms can the pathogen evade the host immune response?

A
  • Polysaccharide capsules to prevent phagocytosis
  • Sheltering in protected zones
  • Producing enzymes to block chemotaxis
  • Blocking of opsonisation
  • Mimicry of antigens
74
Q

Give an example of a protected zone that a pathogen can shelter in?

A

Abscesses

75
Q

How can many pathogens persist?

A

As intacellular pathogens

76
Q

What must intracellular pathogens evade?

A
  • Phagolysosomal fusion
  • Lysosomal enzymes
  • Many other mechanisms
77
Q

What must a pathogen do in order to spread and survive?

A

Move on to the next host directly, enter the environment, or via a vector

78
Q

What can a pathogens new environment serve as?

A

A reservoir for future amplification

Z Old Infection IGNORE (23 decks)

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