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3rd yr- IWB- Microbiology > How bacteria cause disease > Flashcards

How bacteria cause disease Flashcards

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Biology 101 flashcards
1
Q

Define pathogen

A

A microbe capable fo causing host damage/ disease

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2
Q

Define opportunistic pathogen

A

An organism that is a member of the resident microbiota or normally inhabiting the external environment that causes infection under certain circumstances

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3
Q

What does commensal refer to when describing micro organisms

A

Refers to a symbiotic relationship between a microorganism and its host where the micro organism befits from the host and the host is not harmed in the process

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4
Q

Define symbiont

A

A member of the resident microbiota that confers benefit to the host

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5
Q

Define pathbiont

A

A member of the resident microbiota that causes disease when loss of the normal balance between the host and resident microbiota (dysbiosis) occurs

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6
Q

Define dysbiosis

A

Imbalances in the resident human microbiota or our responses to them

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7
Q

Define pathogenicity

A

Capacity of a microbe to cause damage in a host

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8
Q

Define virulence

A

Relative capacity of an organism to cause damage in a host “degree of pathogenicity”

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9
Q

Define virulence determinant/ factor

A

Component of pathogens that damages the host/ allows pathogen to cause disease

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10
Q

How do we write lethal/infectious doses down?

A

LD50/ ID50

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11
Q

What does LD50 refer to?

A

Stands for 50% lethal dose

Number of organisms needed to kill half the host

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12
Q

What does ID50 refer to?

A

Stands for 50% infectious dose

Number of organism needed to cause infection in half the host

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13
Q

List the 4 major steps of the bacterial virulence mechanism

A
  1. Transmission
  2. Adherence to host surface
  3. Invasiveness
  4. Toxigenicity
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14
Q

How can infections be transmitted?

A

Externally or internally

Exogenously or endogenously

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15
Q

What are endogenous infections caused by?

A

Caused by the human microbiota behaving as a opportunistic pathogen

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16
Q

How can endogenous infections be transmitted?

A
  1. Ingestion
  2. Fecal contamination of food and water
  3. Inhalation
  4. Sexually
  5. Contaminated needles
  6. Insect bites
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17
Q

Name the 4 portals of entry for pathogens to get into out body

A
  1. Skin
  2. Respiratory tract
  3. Gastro intestinal tract
  4. Genito urinary tract
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18
Q

Following transmission what is the first step for infections to cause problems in a host?

A

Adherence to host surface

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19
Q

How can microorganism adhere to cell surface?

A
  1. Some have structural adaptations

2. Some produce chemicals to help them adhere to certain surfaces

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20
Q

How does e coli adhere to its host?

A

It has hair like pili that allow it to attach itself directly to the epithelium

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21
Q

How does neisseria gonorrhoea adhere to its host?

A

It has hair like pili that allow it to attach itself directly to the epithelium

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22
Q

How do s mutans adhere to its host?

A

Their extracellular polysaccharide structure help them to adhere to the enamel surface

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23
Q

What are 60% of human infections associated with?

A

The formation of a biofilm

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24
Q

How do bacteria in biofilms maintain their population levels

A

By releasing small amounts of chemicals called form sensing molecules

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25
Q

What are the benefits to bacteria of being in a biofilm

A
  1. Protection from host immune mechanisms
  2. Poor penetration of antimicrobials into deeper layers of the biofilm
  3. Degradation of antimicrobials
  4. Gene expression leading to more virulent or resistant organisms
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26
Q

What is invasiveness dependent on?

A

Depends on secreted bacterial enzymes

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27
Q

Give examples of bacterial enzymes that affect invasiveness

A
  1. Collagenase
  2. Hyaluronidase
  3. Coagulase
  4. Kinase
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28
Q

Where is Hyaluronidase found?

A

Is present in staphylococcus aureus (skin infections) and streptococcus progenes (sore throat)

29
Q

Where is Collagenase found?

A

Is present in clostridium perfringens (gas gangrene)

30
Q

What does coagulase do?

A

It aids in the conversion of fibrologin into fibrin this protects the bacteria from phagocytosis as it clots the micro organism in a fibrin layer

31
Q

What does kinase do?

A

It removes the fibrin layer that coagulase made and helps inject microorganisms into the tissues

32
Q

What does immunoglobulin A (IgA) protease do?

A

Degrades IgA on the mucosal surfaces allowing bacteria to adhere to mucous membranes

33
Q

What does leukocidins

A

Can destroy key classes of host immune cells such as neutrophilic leukocytes and macrophages

34
Q

Give an example of a bacteria that produces leukocidins

A

Aggregatibacter actinomycetemcomitans.

35
Q

Give an example of a bacteria that produces Immunoglobulin A (IgA) protease

A

N. gonorrhoeae, Haemophillus influenza Streptocccus pneumonia

36
Q

What does toxigenicity refer to?

A

Refers to toxin production

37
Q

Name the 2 types of toxins

A

Endotoxins

Exotoxins

38
Q

What are endotoxins

A

The lipid portions of lipopolysaccharides in the cell walls gram negative bacteria

39
Q

When are endotoxins liberated

A

When the bacteria die and their cell wall breaks down

40
Q

Which bacteria are Endo toxins NOT found in?

A

gram positive

41
Q

List some of the biological effects of endotoxins

A
  1. Fever
  2. Hypotension and shock
  3. Activation of the alternative pathway of compliment cascade
  4. Generalised activation of the coagulation system
  5. Increased phagocytic activity of macrophages and polycolonal B cell activation
  6. Increased antibody production
42
Q

How do endotoxins cause biological side effects

A

They lead to the proaction of host factors such as IL1, TNF from macrophages

43
Q

How do endotoxins lead to the development of fever

A

As it leads to the release of IR1 from macrophages which effects the thermoregulatory centre of the hypothalamus and resets the body temperature to a higher temperature

44
Q

Why is the activation of the coagulation system bad ?

A

As it leads to inflammation and tissue ischaemia

45
Q

Describe e coli

A

It is a gut commensal bacteria

It is gram negative

46
Q

What are exo toxins

A

They are protein produced by both gram positive and negative bacteria

47
Q

Which type of bacteria more commonly produces exotoxins

A

Gram positive

48
Q

Give an example of an exotoxin

A

Tentanus toxin
Diptheria
Botulinum

49
Q

What does the tetanus toxin do?

A

It presents the release of the inhabitory neurotransmitter glycine causing muscle spams

50
Q

Name the most toxic compound known

A

Botulinum toxin

51
Q

What does Botulinum toxin do?

A

It blocks the release of acetylene choking at the synapse leading to paralysis of the muscle

52
Q

What is Botulinum toxin

A

It is an obligate anaerobe

Endospore former

53
Q

How can you get infected by Botulinum toxin?

A
  1. Ingesting pre formed toxin in contaminated food
  2. Ingesting the spores
  3. Infection of dirty wounds
54
Q

iWhen we describe a bacteria as being an Endospore former what do we mean?

A

Means the bacteria protects itself by forming a spore which is a lot harder to remove through sterilisation procedures

55
Q

Describe the clinical presentation of botulism

A 
Presents 1-2 days after infection 
Patient can present with:
1. Diplopia 
2. Dysphagia (difficulty swallowing) and speech problems
3. Dry mouth 
4, Respiratory failure 
5. Death
56
Q

List some examples of Endo toxin mediated disease

A
  1. Cholera
  2. Diphtheria
  3. Diarrhoea, pseudomembranous colitis -
  4. Haemorrhagic colitis
  5. Whooping cough
  6. Scarlet fever
  7. Scalded-skin syndrome
57
Q

What is cholera caused by?

A

Vibrio cholerae (enterotoxin)

58
Q

What is Diphtheria caused by?

A

Corynebacterium diphtheriae

59
Q

What is Diarrhoea, pseudomembranous colitis caused by?

A

Clostridium difficile

60
Q

What is Haemorrhagic colitis caused by?

A

E. coli O157 (verotoxin)

61
Q

What is Whooping cough caused by

A

Bordetella pertussis (pertussis toxin)

62
Q

What is Scarlet fever caused by?

A

Streptococcus pyogenes (exotoxins)

63
Q

What is scalded skin syndrome caused by?

A

S. aureus (epidermolysin)

64
Q

List the 5 bacterial virulence factors

A
  1. Adhesin
  2. Invasin
  3. Impedin
  4. Aggressin
  5. Modulin
65
Q

What does Adhesin enable?

A

Enables binding to host tissues

66
Q

What does invasin enable

A

Enables invasion of host cell/ tissues

67
Q

What does impedin enable?

A

Enables avoidance of host cell defence mechanisms

68
Q

What does aggression cause

A

Causes direct damage to the host

69
Q

What does modulin induce

A

Indices indirect damage by perturbing regulation of host defences

3rd yr- IWB- Microbiology (12 decks)

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