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Microbiology for Dentists > 11. Virulence Factors > Flashcards

11. Virulence Factors Flashcards

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Biology 101 flashcards
1
Q

Define ‘commensal’

A

an organism that lives in harmless association with it’s host

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2
Q

Define ‘colonisation’

A

sustained presence of an organism at a body siteD

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3
Q

Define ‘pathogen’

A

an organism that can cause disease in otherwise healthy individuals

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4
Q

Define ‘carriage/carrier state’

A
  • colonisation with a pathogen
  • i.e host can act as source of infection for others but shows no symptoms themselves
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5
Q

Define ‘opportunistic pathogen’

A

an organism which requires the host to have pre-existing defect in its defences before it can cause disease

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6
Q

Define ‘infection’

A

growth of a non-native microorganisms at body site
- with or without damage to host

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7
Q

Define ‘virulence’

A

measure of capacity of an organism to cause diseasee

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8
Q

Define ‘virulence factors’

A

properties of bacterium which contribute to its virulence

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9
Q

Methods of transmission

A
  • body fluids
  • insects
  • skin to skin
  • accident
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10
Q

Define ‘endogenous infections’

A
  • ones caused by infectious agent already present in body
  • has been previously inapparent or dormant
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11
Q

Define ‘exogenous infections’

A

acquired from sources outside of patients

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12
Q

4 examples of virulence factors

A
  • adhesins
  • invasins
  • toxins
  • extracellular enzymes
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13
Q

Why do bacteria have virulence factors?

A
  • part of their survival strategy
  • allows multiplication in host
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14
Q

What disease is caused by bordetella pertussis?

A

hooping cough

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15
Q

What disease is caused by neisseria gonorrhoeae?

A

gonorrhoeae

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16
Q

What disease is caused by yersinia pestis?

A

plague/black death

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17
Q

What disease is caused by bacillus anthracis?

A

anthrax

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18
Q

List 3 opportunistic pathogens and what they cause?

A
  • staphylococcus epidermidis (endocarditis and issues in catheters)
  • pseudomonas aeruginosa (infects burns)
  • escherichia coli (diarrhoea)
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19
Q

Stages of infection

A
  • exposure to pathogen
  • adherance to skin or mucous
  • invasion through epithelium
  • infection (growth and production of virulence factors and toxins)
  • toxicity (local and systemic effects) and invasiveness (further growth at original sites and distant ones)
  • causes tissue damage and disease
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20
Q

Explain adherance of disease

A
  • initial attachment involves interaction between surface structure of bacteria and host tissue
  • bacteria surface is pili, fimbriae, surface proteins
  • host tissue receptors are glycoproteins, tissue-specific antigens
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21
Q

How does E.Coli adhere?

A
  • with type 1 pili
  • adhere to epithelial cells in urinary tract
22
Q

How does vibrio cholerae adhere?

A
  • highly mobile
  • swims through intestinal mucus and attaches to receptors in gut wall
23
Q

List innate host defence against infection

A
  • skin
  • flushing
  • secretions
  • mucous membranes
  • normal bacterial population
24
Q

List adaptive host defence against infection

A
  • phagocytosis
  • inflammation, fever
  • antibodies
25
Q

How does skin defend against infection?

A
  • keratinsases
  • skin penetration
26
Q

How does flushing defend against infection?

A
  • adherance
  • motility
27
Q

How does secretions defend against infection?

A
  • lysozyme resistant walls
  • tolerance to salts, bile, pH etc
28
Q

How does mucous membranes defend against infection?

A
  • degrade
  • or swim
    through mucin
29
Q

How does commensal flora/normal bacteria defend against infection?

A
  • metabolic end products
  • bacteriocins
  • bacteriophage
30
Q

How does phagocytosis defend against infection?

A

capsules

31
Q

How does inflammation/fever defend against infection?

A

heat shock response

32
Q

How does antibodies defend against infection?

A
  • breakdown of immunoglobins
  • kill host defence cells
  • intracellular growth
  • antigenic variation
33
Q

Explain invasion in infection

A
  • invasion into bloodstream - bacteraemia
  • infection in blood is septicaemia
  • after attachment, some bacteria invade epithelial cells
34
Q

Disease arises from infection when …

A
  • damage to host occurs
  • infection is just the introduction of a microorganism that isnt a natural coloniser
35
Q

For growth, bacteria must obtain what?

A
  • nutrients (inc. trace metals like iron)
  • correct oxygen environment
36
Q

Explain invasion/spreading of infection

A
  • through lungs, gut, urinary tract, blood
  • via sinuses and body cavities
  • tracks along nerve pathways from cell to cell
  • causes tissue breakdown
37
Q

2 types of toxins

A
  • endotoxins
  • exotoxins
38
Q

3 tissue-degrading enzymes

A
  • collagenase
  • hyaluronidase
  • haemolysin
39
Q

1 example of an endotoxin

A

lipopolysaccharide

40
Q

Explain LPS as an endotoxin

A
  • found in gram negative bacteria in the outer layer of the outer membrane
  • released in growth or when bacteria die and lyse
  • causes fever, septic shock and local inflammation
41
Q

Exotoxins are secreted by … and are produced by …
They are stable/unstable
Toxic/non-toxic?

A
  • bacteria
  • some gram pos and neg bacteria species
  • relatively unstable (heat-sensitive)
  • highly toxic (1 nanogram of botulism toxin can be fatal)
42
Q

Examples of exotoxins and their effects

A
  • tetanus attacks nervous system and causes lock jaw
  • botulism attacks motor nerve causing paralysis
  • diphtheria stops cell protein synthesis
43
Q

Damage from exotoxins doesn’t always need bacterial infection. Example of this?

A
  • preformed staphylococcal enterotixon in food
  • causes rapid onset food poisoning
  • antibiotics are useless and vaccines need to target toxin rather than infectious agent
44
Q

What bacteria causes tetanus?

A

clostridium tetani

45
Q

Tetanus bacteria is gram … and a … rod
Found in …
How does it cause disease?
Symptoms

A
  • positive
  • spore forming
  • soil and animal faeces
  • secretes a powerful neurotoxin that blocks release of neurotransmitters from presynaptic membranes of inhibitory nerve synapses
  • lockjaw, muscular contraction
46
Q

Botulism is linked to what bacteria?
It’s found where?
How to inactivate toxin?

A
  • clostridium botulinum
  • soil, water, foodstuffs like honey
  • extremely potent inactivated by cooking
  • tinned foods undergo a botulinum cook at 121 degrees celc for 3 mins
47
Q

How is botulinum toxin used?

A
  • for botox
  • treats muscle conditions
  • removes wrinkles by temporarily relaxes muscles
  • and for murder (poison tip umbrella assasination of Markov)
48
Q

Bacteria between diphtheria?
Where is gene carried?
What does it do?
How to stop it?

A
  • corynebacterium diphtheriae
  • carried on bacteriophage
  • inhibits proteinsynthesis
  • vaccine based on inactivated toxin is highly effective
49
Q

Explain necrotising fasciitis?

A
  • rapidly spreading
  • tissue destruction by toxins which initiate an overactive immune response
  • can be single organism or polymicrobial (most common are streptococcus pyogenes or MRSA)
  • treatment by surgical debridement
50
Q

Explain resolution in infection

A
  • for acute it’s a short duration (days)
  • for chronic longer (weeks to months)
51
Q

Example of a chronic lung condition

A
  • TB
  • can show granuloma on scans where infection is controlled but not resolved
52
Q

Factors that increase susceptibility to disease

A
  • trauma (accidental or intentional like surgery)
  • underlying disease (HIV immunosuppression etc)
  • age
  • genetic constitution
  • nutrition
  • hormonal factors and stress
  • pollutants

Microbiology for Dentists (37 decks)

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