Nosocomial

Question 1

List the microbial factors and host (risk) factors leading to an increased risk of infection

Answer 1

Microbial

• Resistance
• Virulence/Transmissibility
• Survival ability
• Ability to evade host defences

Host

• Devices - PVC, CVC, catheter, ventilation
• Antibiotics
• Break in skin surface
• Foreign body
• Immunosuppression
• ?gastric acid suppression
• Age extremes
• Overcrowding
• Increased opportunity for transmission e.g. interventions, hands

Question 2

List the main modes of transmission of microbes and which microbes are largely transmitted by which route.

Answer 2

Direct contact - SA, coliforms
Respiratory/droplet - neisseria, mycobacteria TB
Faecal/oral - C diff, salmonella
Penetrating injury - group A strep, BBV

Question 3

Measures/protocols that can be used by healthcare systems to break the chain of infection

Answer 3

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

Question 4

Define what is meant by ‘cleaning’, ‘disinfection’ and ‘sterilisation’ and give examples of how these are achieved and when they are used

Answer 4

Cleaning - physical removal of organic material and decrease in microbial load - used when only low risk of transmission e.g. contact with intact skin

Disinfection - large reduction in microbes - heat or chemical - used for medium risk e.g. mucous membrane contact

Sterilisation - removal/destruction of ALL microbes/spores - pressurised steam/hot air oven/gas/radiation - used for high risk e.g. surgical instruments

Question 5

Describe methods to confirm an outbreak of a particular pathogen, and measures that can be taken to reduce its spread

Answer 5

Typing necessary to determine if the same strain present i.e. an outbreak
Methods - antibiogram, phage typing, pyocin typing, serotyping, molecular typing

Control measures

• single room isolation
• cohorting of cases
• clinical area/ward closure
• re-inforcement of IPC measures
• staff exclusion (e.g. colonise staff in case of MRSA, non-immune staff in case of VZV, measles etc.
• staff decolonisation or other measures