Infection: An infection Model

Question 1

Briefly outline the infection model

Answer 1

Pathogen + patient –(mechanism of infection)–> infection —> management (diagnosis and treatment) –> outcome

Question 2

What are some patient factors that need to be considered when using the infection model?

Answer 2

Age - the risk of infections changes with age eg 3m-3yrs susceptible to meningitis
Gender - UTIs common in women and rare in men
Physiological state - pH of vagina changes with cycle can get candida infections
Pathological state - comorbidities, surgery, central lines
Social factors - STIs
Place - recent travel Hx

Question 3

What are the possible mechanisms of infection?

Answer 3

Contiguous spread - commensals transferred to wrong site
Inoculation - blood stick injuries
Haematogenous - any spread through blood stream eg endocarditis from mouth bacteria
Ingestion - faecal oral transmission
Inhalation - droplets or aerosols
Vector - malaria spread
Vertical transmission - mother to child across placenta or from vagina or breast feeding

Question 4

What are endotoxins and exotoxins?

Answer 4

Exotoxins are toxins deliberately released by the pathogen into the environment
Endotoxins are released by the break down of bacteria

Question 5

Give some examples of specific and supportive treatments?

Answer 5

Specific:
Antimicrobials
Surgery - drainage of pus, debridement, dead space removal eg in necrotic bone

Supportive:
Symptomatic relief
Physiological restoration - controlling pO2, pCO2, lactic acid etc

Question 6

What are the possible outcomes of infection?

Answer 6

Cure
Death
Or chronic infection