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Dermatology > Virulence > Flashcards

Virulence Flashcards

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Dermatology Board Prep flashcards
1
Q

What 3 things should be considered in infectious diseases

A

Symptoms
Organism
Virulence Factors

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2
Q

What part of the skin prevents colonisation of micro-organisms

A

The waterproof epithelial surface is constantly shedding and waterproof

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3
Q

Bacteria require iron. How do they obtain this

A

They rely on haemolysis of RBCs

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4
Q

What is virulence

A

The capacity of a microbe to cause damage to the host.
i.e what amount of organisms are required to cause death to the host
A measure of how well they can cause disease

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5
Q

What is adhesin

A

Enables binding of the organism to host tissue

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6
Q

What is invasin

A

Enable the organism to invade a host cell/ tissue

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7
Q

What is Impedin

A

Enables the organism to avoid host defence mechanisms

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8
Q

What is aggressin

A

Causes damage to the host directly

It affects the hosts ability to respond to diseas

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9
Q

What is Modulin

A

Induces damage to the host indirectly

Turn the immune system in in itself

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10
Q

What can lead to the amputation of limbs

A

Aggressins

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11
Q

What are the 3 main skin microbiota

A

Staplococci spp
Staphlococcus aureus
Diptheroids

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12
Q

If staph aureus is acquired in the community, what does it tend to lead to?

A

Serious skin infection

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13
Q

Staph epidermidiis is carried on most people but it only affects some. Who are these people

A

Immunocompromised

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14
Q

Who is at risk of developing MRSA

A 
elderly and immunocrompromised
ICU
Burns patients
surgical patients
IV lines 
Dialysis patients
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15
Q

Define nosocomial

A

Hospital borne infection

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16
Q

Why is staph aureus classed as a successful organism

A

Because it is so adaptive and therefore can survive in different environments

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17
Q

What makes a an organism successful

A

The number of virulence factors that lead to the organism to being adaptive

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18
Q

Name some virulence factors

A 
Capsule
Fibrinogen Binding protein
Coagulase
Leukocidin
TSST-1 (toxin)
Enterotoxin
Adhesin
Clots plasma
Digests fibrin
Kills Leukocytes
Vomiting and Diarrhoea
Shock, rash, desquamation
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19
Q

Why might staph aureus cause a different reaction in different areas of the body?

A

Its ability to produce different virulence factors causing differences in disease

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20
Q

Give 2 examples of Adhesins

A

Fibrinogen-Binding (ClfA and ClfB)

Collagen-Binding (CNA)

21
Q

How does protein A work to cause disease?

A

It stops the immune system from working as it binds the wrong immunoglobulin

22
Q

What does PVL stand for

A

Panton Valentine Leukocidin

23
Q

What is PVL and alpha toxin linked with

A

CA-MRSA

24
Q

Describe the progression of necrotising pneumonia

A

Rapid progression

25
Q

Why does giving a patient with necrotising pneumonia not help

A

The tissue is already being destroyed and the damage has already been made and is therefore too late to reverse this.

26
Q

What superantigen is associated with Toxic shock

A

TSST-1

27
Q

What does TSST-1 do

A

Cause a massive release of cytokines and an inappropriate immune response

28
Q

Where does the super antigen become stabalised

A

Outside the cell and not in the cleft

29
Q

What 4 things must a patient have for them to be diagnosed with a superantigen

A

Fever (39)
Diffuse macular rash and desquamation
Hypotension (

30
Q

Describe the appearance of Streptococcus pyogenes

A

Gram +ve cocci
Chains
Catalase negative
Haemolysis

31
Q

What skin infections are caused by streptococucus pyogenes

A

Impetigo
Cellulitis
Necrotising Fascites

32
Q

What is the most common presentation of an infection of Streptococcus pyogenes

A

Sore throat

33
Q

What is the purpose of the Lancefield system

A

it organises different groups of streptococci

Serotyping of the cell wall carbohydrate

34
Q

What is the most important protein for adhesion

A

The M protein

35
Q

How does the capsule work

A

It is part of the defences - it is an extracellular matrix that disguises the microbia

36
Q

What makes up the capsule

A

Hyaluronic acid

37
Q

What is the most common GAS skin disease

A

Impetigo

38
Q

Give some features of Impetigo

A

Usually affects the face

highly contagious through contact with discharge on the face

39
Q

What is the difference between Impetigo and Cellulitis

A

Impetigo is just below the surface of the skin in the stratum corneum
Cellulitis is a deeper skin infection not associated with necrosis

40
Q

What generally happens with necrotising fasciitis

A

Damage to the tissue tends to be so bad that it leads to amputation

41
Q

Toxic shock like syndrome TSLS is often associated with what

A

A pre-determined sore throat

42
Q

What is the mortality rate with Pyrogenic exotoxins

A

30%

43
Q

What is the onset of pyrogenic exotoxin

A

hours to days

44
Q

What doesStreptococcus pyogenes target

A

White blood cells and the immune system

45
Q

What two organisms can cause toxic shock

A

Staph aureus and Staph pyogenes

46
Q

How does virulence vary

A

Variation caused by evolution- some proteins have an advantage of surviving in one environment than another

47
Q

Where is Staph pyogenes normally found

A

In the pharynx and also adheres to skin

48
Q

How can toxic shock be produced by both staph aureus and staph pyogenes

A

Due to their production of similar exo-proteins

Dermatology (21 decks)

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