11. Virulence Factors Flashcards
(52 cards)
1
Q
Define ‘commensal’
A
an organism that lives in harmless association with it’s host
2
Q
Define ‘colonisation’
A
sustained presence of an organism at a body siteD
3
Q
Define ‘pathogen’
A
an organism that can cause disease in otherwise healthy individuals
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
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
6
Q
Define ‘infection’
A
growth of a non-native microorganisms at body site
- with or without damage to host
7
Q
Define ‘virulence’
A
measure of capacity of an organism to cause diseasee
8
Q
Define ‘virulence factors’
A
properties of bacterium which contribute to its virulence
9
Q
Methods of transmission
A
- body fluids
- insects
- skin to skin
- accident
10
Q
Define ‘endogenous infections’
A
- ones caused by infectious agent already present in body
- has been previously inapparent or dormant
11
Q
Define ‘exogenous infections’
A
acquired from sources outside of patients
12
Q
4 examples of virulence factors
A
- adhesins
- invasins
- toxins
- extracellular enzymes
13
Q
Why do bacteria have virulence factors?
A
- part of their survival strategy
- allows multiplication in host
14
Q
What disease is caused by bordetella pertussis?
A
hooping cough
15
Q
What disease is caused by neisseria gonorrhoeae?
A
gonorrhoeae
16
Q
What disease is caused by yersinia pestis?
A
plague/black death
17
Q
What disease is caused by bacillus anthracis?
A
anthrax
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)
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
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
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
How does skin defend against infection?
- keratinsases
- skin penetration
26
How does flushing defend against infection?
- adherance
- motility
27
How does secretions defend against infection?
- lysozyme resistant walls
- tolerance to salts, bile, pH etc
28
How does mucous membranes defend against infection?
- degrade
- or swim
through mucin
29
How does commensal flora/normal bacteria defend against infection?
- metabolic end products
- bacteriocins
- bacteriophage
30
How does phagocytosis defend against infection?
capsules
31
How does inflammation/fever defend against infection?
heat shock response
32
How does antibodies defend against infection?
- breakdown of immunoglobins
- kill host defence cells
- intracellular growth
- antigenic variation
33
Explain invasion in infection
- invasion into bloodstream - bacteraemia
- infection in blood is septicaemia
- after attachment, some bacteria invade epithelial cells
34
Disease arises from infection when ...
- damage to host occurs
- infection is just the introduction of a microorganism that isnt a natural coloniser
35
For growth, bacteria must obtain what?
- nutrients (inc. trace metals like iron)
- correct oxygen environment
36
Explain invasion/spreading of infection
- through lungs, gut, urinary tract, blood
- via sinuses and body cavities
- tracks along nerve pathways from cell to cell
- causes tissue breakdown
37
2 types of toxins
- endotoxins
- exotoxins
38
3 tissue-degrading enzymes
- collagenase
- hyaluronidase
- haemolysin
39
1 example of an endotoxin
lipopolysaccharide
40
Explain LPS as an endotoxin
- 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
Exotoxins are secreted by ... and are produced by ...
They are stable/unstable
Toxic/non-toxic?
- bacteria
- some gram pos and neg bacteria species
- relatively unstable (heat-sensitive)
- highly toxic (1 nanogram of botulism toxin can be fatal)
42
Examples of exotoxins and their effects
- tetanus attacks nervous system and causes lock jaw
- botulism attacks motor nerve causing paralysis
- diphtheria stops cell protein synthesis
43
Damage from exotoxins doesn't always need bacterial infection. Example of this?
- preformed staphylococcal enterotixon in food
- causes rapid onset food poisoning
- antibiotics are useless and vaccines need to target toxin rather than infectious agent
44
What bacteria causes tetanus?
clostridium tetani
45
Tetanus bacteria is gram ... and a ... rod
Found in ...
How does it cause disease?
Symptoms
- 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
Botulism is linked to what bacteria?
It's found where?
How to inactivate toxin?
- 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
How is botulinum toxin used?
- for botox
- treats muscle conditions
- removes wrinkles by temporarily relaxes muscles
- and for murder (poison tip umbrella assasination of Markov)
48
Bacteria between diphtheria?
Where is gene carried?
What does it do?
How to stop it?
- corynebacterium diphtheriae
- carried on bacteriophage
- inhibits proteinsynthesis
- vaccine based on inactivated toxin is highly effective
49
Explain necrotising fasciitis?
- 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
Explain resolution in infection
- for acute it's a short duration (days)
- for chronic longer (weeks to months)
51
Example of a chronic lung condition
- TB
- can show granuloma on scans where infection is controlled but not resolved
52
Factors that increase susceptibility to disease
- trauma (accidental or intentional like surgery)
- underlying disease (HIV immunosuppression etc)
- age
- genetic constitution
- nutrition
- hormonal factors and stress
- pollutants
