Healthcare Acquired Infection

Question 1

Define Healthcare Acquired Infections (HAI)

Answer 1

Infections that were not present or in pre-symptomatic phase at the time of admission to hospital, which arise >= 48 hours after admission or within 48 hours of discharge

Question 2

What is the difference between colonisation and infection?

Answer 2

Colonisation refers to the presence of an organism in or on the body without causing harm/symptoms, whereas infection refers to the breaching of immune barriers by an organism, resulting in symptomatic illness

Question 3

What are the microbial factors leading to an increased risk of infection? (5)

Answer 3

• Resistance
• Virulence
• Transmissability
• Increased survival ability
• Ability to evade host defences

Question 4

What are the host factors leading to an increased risk of infection? (9)

Answer 4

• Devices (PVC, CVC, urinary catheter, ventilation)
• Antibiotics
• Break in skin surface
• Foreign body
• Immunosuppression
• Gastric acid suppression
• Age extremes
• Overcrowding
• Increased opportunity for transmission (e.g. interventions, inadequate hand hygiene)

Question 5

What is the Chain of Infection?

Answer 5

Source of microbe&raquo_space; Transmission&raquo_space; Host

Question 6

What are the main modes of transmission of microbes? Give examples of organisms which spread by each method. (4)

Answer 6

• Direct contact (S. aureus, coliforms)
• Respiratory/droplet (Neisseria meningitidis, mycobacteria tuberculosis)
• Faecal-oral (C. difficile, Salmonella)
• Penetrating injury (Group A strep, blood-borne viruses)

Question 7

Methods of breaking the chain of infection (7)

Answer 7

• Risk awareness
• Standard infection prevention and control precautions (SICPs)
• Hand hygiene
• Appropriate PPE
• Vaccination
• Post-exposure prophylaxis
• Environment

Question 8

Define cleaning

Answer 8

Physical removal of organic material and decrease in microbial load

Question 9

Define disinfection

Answer 9

Large reduction in microbe numbers - spores may remain

Question 10

Define sterilisation

Answer 10

Removal/destruction of all microbes and spores

Question 11

What is an appropriate method of cleaning?

Answer 11

• Following manufacturer’s instructions (usually detergent and water) -
  drying is important

(Essential prior to disinfection and sterilisation, if required)

Question 12

What are appropriate methods of disinfection? (2)

Answer 12

Heat (pasteurisation or boiling)

Chemical (e.g. alcohol, hydrogen peroxide)

Question 13

What are appropriate methods of sterilisation? (4)

Answer 13

• Steam under pressure (autoclave)
• Hot air oven
• Gas (ethylene dioxide)
• Ionising radiation

Question 14

Define an outbreak

Answer 14

2 or more cases of an infection linked in time and place

Question 15

What are appropriate control measures for an outbreak? (6)

Answer 15

• Single room isolation
• Cohorting of cases
• Clinical area/ward closure
• Re-inforcement of infection prevention and control measures
• Staff exclusion (depending on outbreak - colonised staff, non-immune staff)
• Staff decolonisation or other measures