1. Introduction

Question 1

What is an infection?

Answer 1

Invasion of a host’s tissues by microorganisms and disease caused by microbial multiplication, toxins and host response

Question 2

What are microbiota/commensals?

Answer 2

Microorganisms carried on skin and mucosal surfaces
Normally harmless or even beneficial
Transfer to other sites can be harmful

Question 3

How can people get infections?

Answer 3

Physical contact
Airborne spread
Vector

Question 4

What are the modes of horizontal transmission?

Answer 4

Contact - direct, indirect, vectors
Inhalation - droplets, aerosols
Ingestion - faecal-oral transmission

Question 5

What is the difference between droplets and aerosols?

Answer 5

Droplets drop soon after being in air

Aerosols remain suspended in air for long time

Question 6

What is vertical transmission?

Answer 6

Mother to child, before or after birth

Question 7

What are the 5 steps for microorganisms to cause disease?

Answer 7

Exposure
Adherence
Invasion
Multiplication
Dissemination

Question 8

What are virulence factors?

Answer 8

Survival factors

What microorganisms produce

Question 9

What are exotoxins?

Answer 9

Released to local environment by microorganisms, released into host cells

Question 10

Name 4 exotoxins

Answer 10

Cytolytic
AB toxins
Superantigens
Enzymes

Question 11

What are endotoxins?

Answer 11

Part of microorganism membrane

Host recognises it and indicates invasion

Question 12

What are a pathogens disease determinants?

Answer 12

Violence factors
Inoculum size - threshold, if under may be insufficient to cause disease
Antimicrobial resistance

Question 13

What are the patients disease determinants?

Answer 13

Site of infection

Co-morbidities

Question 14

What are the questions to answer in a patient with suspected infection?

Answer 14

Is there an infection?
Where is the infection?
What is the cause of the infection?
What is the best treatment?

Question 15

How do we know if patients have an infection?

Answer 15

History
Examination
Investigations

Question 16

What does a history include if an infection is suspected?

Answer 16

Symptoms - focal/systemic, severity, duration

Potential exposures

Question 17

What questions are asked relating to potential exposures of a patient?

Answer 17

Where have you been?
What have you been doing?
Who were you doing it with?
Were animals involved?

Question 18

What supportive investigations are done to determine if there is an infection?

Answer 18

Full blood count - neutrophils and lymphocytes
C-reactive protein
Blood chemistry - liver and kidney function tests
Imaging
Histopathology

Question 19

What are the bacteriology investigations to determine if an infection is present?

Answer 19

Specimen types - swabs, fluids, tissues
M, C & S - microscopy, culture, antibiotic susceptibility
Antigen detection
Nucleic acid detection