Microbiology 1

Question 1

What does virulence mean?

Answer 1

The capacity of a microorganism to cause damage to a host

Question 2

What is a virulence factor?

Answer 2

A specific component of a pathogen which causes a disease

Question 3

What type of virulence factor enables binding of the organism to host tissue?

Answer 3

Adhesin

Question 4

What does invasin do?

Answer 4

Enables the organism to invade a host cell/tissue

Question 5

What type of virulence factor enables the organism to avoid host defence mechanisms?

Answer 5

Impedin

Question 6

What does aggressin do?

Answer 6

Causes damage to the host directly

Question 7

What type of virulence factor induces damage to the host indirectly?

Answer 7

Modulin

Question 8

What is transient flora? Give an example.

Answer 8

Infections which occur because the skin is not washed/dried properly. An example would be staph aureus hand carriage.

Question 9

Will every strain of the same bacteria contain all the same virulence factors?

Answer 9

No

Question 10

Multiple conditions can come out of infection with Staph. Aureus, what are some examples of these?

Answer 10

• Superficial lesions
• Systemic life-threatening disease
• Toxic shock/SSS

Question 11

Who are some at risk groups for infection with MRSA?

Answer 11

Elderly, immunocompromised, ITU/burns/surgical wards, IV lines, dialysis patients

Question 12

Recurrent skin infections are fairly common in who?

Answer 12

Those who are colonised with Staph. Aureus

Question 13

What % of the population are colonised with Staph Aureus?

Answer 13

20%

Question 14

What microorganism is all of the population colonised with in the skin and mucosal membranes?

Answer 14

Staph Epidermidis

Question 15

Staph Epidermidis infections are associated with what?

Answer 15

Foreign devices e.g. catheters

Question 16

What do superantigens do?

Answer 16

They are able to evade host defences by binding to the host in a less variable region

Question 17

What is the toxin associated with toxic shock syndrome?

Answer 17

TSST-1 (a superantigen)

Question 18

What happens immunologically when the body is infected with TSST-1?

Answer 18

A massive release of cytokines and inappropriate immune response

Question 19

How quickly does toxic shock syndrome progress?

Answer 19

Rapidly, over 48 hours

Question 20

What are the 4 main diagnostic criteria for toxic shock syndrome?

Answer 20

• Fever > 39 degrees
• Diffuse macular rash and desquamination
• Hypotension < 90 systolic
• 3 or more organs involved

Question 21

Apart from the main diagnostic criteria, what are some other symptoms of toxic shock syndrome?

Answer 21

• Vomiting
• Diarrhoea
• Sore throat
• Muscle pain

Question 22

What is the diagnostic test for toxic shock syndrome?

Answer 22

Coagulase

Question 23

What organism and toxin causes toxic shock syndrome?

Answer 23

Staph. Aureus

TSST-1 (menstrual)

Question 24

What organism and toxin causes toxic shock like syndrome?

Answer 24

Strep. Pyogenes

SpeC/SpeA toxins

Question 25

Where is strep. pyogenes normally found in the body? What may it cause here?

Answer 25

Pharynx- may cause pharyngitis

Question 26

What cells of the body does PVL target?

Answer 26

Leukocytes

Question 27

What are some conditions that PVL is associated with?

Answer 27

- Sepsis - Necrotising fasciitis - Recurrent furunculosis

Question 28

When does necrotising pneumonia occur? What is it a major complication of?

Answer 28

Preceding an influenza like syndrome, it is a major complication of CAP

Question 29

What happens in necrotising pneumonia?

Answer 29

Rapid progression to acute respiratory distress, deterioration of pulmonary function and hypoxaemia. There is usually multi-organ failure despite antibiotic therapy.

Question 30

What toxin causes SSS?

Answer 30

Exfoliatin toxin (from staph aureus)

Question 31

Where and who does SSS normally affect?

Answer 31

The face, axilla and groin of neonates