2. Chain of Infection

Question 1

What is the infectious agent?

Answer 1

The microorganism with the ability to cause disease e.g. bacteria, fungi, viruses, parasites or prions.

Question 2

Why do infections commonly occur in healthcare environments?

Answer 2

Exposure to microorganisms
Immunosuppressed hosts
Natural defences breached - breaking of skin
Microorganisms reach an area where they do not normally live e.g. skin to bloodstream

Question 3

How would you take a specimen to identify a microorganism?

Answer 3

PPE worn when handling
Specimen container sealed, labelled & bagged
Specimen form filled out
Know procedure following specimen spillage

Question 4

What microorganisms can survive in damp areas?

Answer 4

pseudonomas aeruginosa

Question 5

What microorganism can be found in dust/dry conditions?

Answer 5

MRSA

Question 6

What microorganism can be found on shared equipment?

Answer 6

Clostridium difficile

Question 7

What microorganism can be found in food?

Answer 7

Salmonella

Question 8

What are different means of exit?

Answer 8

Excretions e.g. diarrhoea, vomiting
Secretions e.g. body fluids like blood/saliva
Droplets e.g. coughing & sneezing
Skin e.g. scale

Question 9

What are some modes of transmission?

Answer 9

Direct contact e.g. hands
Indirect contact e.g. via equipment
Inhalation
Inoculation
Ingestion
Intercourse
Mother to infant transmission

Question 10

What are the six stages of the chain of infection?

Answer 10

1. Infectious agent
2. Reservoir
3. Means of exit
4. Mode of transmission
5. Means of entry
6. Susceptible host
   IRETES

Question 11

What are means of entry?

Answer 11

Arise from invasive procedures which damage the body’s normal defences and provide a means of entry.
Surgical sites, GIT, broken skin, UT, bloodstream

Question 12

What factors make a susceptible host?

Answer 12

Weakened immune system
Malnourished
Shared facilities - with other patients, confined space
Dependency on staff to help with daily activities

Question 13

What are intrinsic risks?

Answer 13

Risks associated with the patient

e.g. age extremes, diseases, lifestyle factors

Question 14

What are extrinsic risks?

Answer 14

Risks external to the patient
Things ‘done to’ the patient e.g. surgery, urinary catheterisation
Patient becomes largely dependent on the safety of the patients

Question 15

What is the chain of infection for C. difficile?

Answer 15

I - C. diff
R - gut
E - faeces, diarrhoea
T - airborne (spores), direct contact with faecal matter, indirect contact via equipment or shared environment
E - GIT
S - very young/elderly, immunosuppressed patients, patients recieving antibiotics