Virulence

Question 1

What 3 things should be considered in infectious diseases

Answer 1

Symptoms
Organism
Virulence Factors

Question 2

What part of the skin prevents colonisation of micro-organisms

Answer 2

The waterproof epithelial surface is constantly shedding and waterproof

Question 3

Bacteria require iron. How do they obtain this

Answer 3

They rely on haemolysis of RBCs

Question 4

What is virulence

Answer 4

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

Question 5

What is adhesin

Answer 5

Enables binding of the organism to host tissue

Question 6

What is invasin

Answer 6

Enable the organism to invade a host cell/ tissue

Question 7

What is Impedin

Answer 7

Enables the organism to avoid host defence mechanisms

Question 8

What is aggressin

Answer 8

Causes damage to the host directly

It affects the hosts ability to respond to diseas

Question 9

What is Modulin

Answer 9

Induces damage to the host indirectly

Turn the immune system in in itself

Question 10

What can lead to the amputation of limbs

Answer 10

Aggressins

Question 11

What are the 3 main skin microbiota

Answer 11

Staplococci spp
Staphlococcus aureus
Diptheroids

Question 12

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

Answer 12

Serious skin infection

Question 13

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

Answer 13

Immunocompromised

Question 14

Who is at risk of developing MRSA

Answer 14

elderly and immunocrompromised
ICU
Burns patients
surgical patients
IV lines 
Dialysis patients

Question 15

Define nosocomial

Answer 15

Hospital borne infection

Question 16

Why is staph aureus classed as a successful organism

Answer 16

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

Question 17

What makes a an organism successful

Answer 17

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

Question 18

Name some virulence factors

Answer 18

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

Question 19

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

Answer 19

Its ability to produce different virulence factors causing differences in disease

Question 20

Give 2 examples of Adhesins

Answer 20

Fibrinogen-Binding (ClfA and ClfB)

Collagen-Binding (CNA)

Question 21

How does protein A work to cause disease?

Answer 21

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

Question 22

What does PVL stand for

Answer 22

Panton Valentine Leukocidin

Question 23

What is PVL and alpha toxin linked with

Answer 23

CA-MRSA

Question 24

Describe the progression of necrotising pneumonia

Answer 24

Rapid progression

Question 25

Why does giving a patient with necrotising pneumonia not help

Answer 25

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

Question 26

What superantigen is associated with Toxic shock

Answer 26

TSST-1

Question 27

What does TSST-1 do

Answer 27

Cause a massive release of cytokines and an inappropriate immune response

Question 28

Where does the super antigen become stabalised

Answer 28

Outside the cell and not in the cleft

Question 29

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

Answer 29

Fever (39) Diffuse macular rash and desquamation Hypotension (

Question 30

Describe the appearance of Streptococcus pyogenes

Answer 30

Gram +ve cocci Chains Catalase negative Haemolysis

Question 31

What skin infections are caused by streptococucus pyogenes

Answer 31

Impetigo Cellulitis Necrotising Fascites

Question 32

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

Answer 32

Sore throat

Question 33

What is the purpose of the Lancefield system

Answer 33

it organises different groups of streptococci | Serotyping of the cell wall carbohydrate

Question 34

What is the most important protein for adhesion

Answer 34

The M protein

Question 35

How does the capsule work

Answer 35

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

Question 36

What makes up the capsule

Answer 36

Hyaluronic acid

Question 37

What is the most common GAS skin disease

Answer 37

Impetigo

Question 38

Give some features of Impetigo

Answer 38

Usually affects the face | highly contagious through contact with discharge on the face

Question 39

What is the difference between Impetigo and Cellulitis

Answer 39

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

Question 40

What generally happens with necrotising fasciitis

Answer 40

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

Question 41

Toxic shock like syndrome TSLS is often associated with what

Answer 41

A pre-determined sore throat

Question 42

What is the mortality rate with Pyrogenic exotoxins

Answer 42

30%

Question 43

What is the onset of pyrogenic exotoxin

Answer 43

hours to days

Question 44

What doesStreptococcus pyogenes target

Answer 44

White blood cells and the immune system

Question 45

What two organisms can cause toxic shock

Answer 45

Staph aureus and Staph pyogenes

Question 46

How does virulence vary

Answer 46

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

Question 47

Where is Staph pyogenes normally found

Answer 47

In the pharynx and also adheres to skin

Question 48

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

Answer 48

Due to their production of similar exo-proteins