S2 Infection Model

Question 1

What is the infection model?

Answer 1

1. Pathogen + patient
2. Mechanism of infection
3. Infection
4. Management
5. Outcome

Question 2

What are the different types of pathogen?

Answer 2

• virus
• prokaryotes - bacterium
• eukaryotes - fungus (yeast and mould) and parasites (protazoa and helminth (worm))

Question 3

What factors affect the patient?

Answer 3

• person - age, gender, physiological state, pathological state, social factors
• time - calendar time, relative time
• place - current, recent

Question 4

What are the mechanisms of infection?

Answer 4

• contiguous (direct) spread e.g. touch
• inoculation e.g. scratch
• haematogenous e.g. mouth —> blood —> heart valve
• ingestion e.g. into GI tract
• inhalation e.g. respiratory infections
• vector e.g. malaria (mosquitos)
• vertical transmission e.g. mother to child

Question 5

How does the infection occur?

Answer 5

1. Attachment
2. Toxin produced
3. Host damage

Or

2. Interaction with host defences
3. Inflammation or host damage
4. Host damage

Question 6

What does the management aspect of the infection model involve?

Answer 6

1. History (diagnosis)
2. Examination (diagnosis)
3. Investigations (diagnosis)
4. Treatment (specific or supportive)
5. Infection prevention (hospital or community)

Question 7

What does the treatment aspect of the infection model involve?

Answer 7

• specific - antimicrobials, surgery (drainage, debridement, dead space removal)
• symptom relief
• physiological restoration

Question 8

What do you want to prevent in infection prevention in hospital and community?

Answer 8

Want to prevent transmission to other patients, staff and other contacts

Question 9

What is debridement?

Answer 9

Removal of dead/dying tissue as it’s a source of nutrients for bacteria

Question 10

What is specific vs supportive treatment?

Answer 10

• specific - aimed at killing the microorganism e.g. antibiotics
• supportive - aiming to help ease infection symptoms e.g if you have a viral infection drugs like antibiotics won’t kill it and it will usually die anyways (self-limiting) so use things like paracetamol

Question 11

What is the outcome in the infection model?

Answer 11

Cure or death

Could lead to a chronic infection or give/remove a disability