Approach to Disinfection and Sterilisation – Definition of Key Terms

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• Cleaning — The removal of visible soil (organic & inorganic material) from objects and surfaces.
  • It can be a manual or mechanical process using water with detergents or enzymatic products.
  • It is essential to complete cleaning before the high-level disinfection and sterilisation.
  • The visible soil will interfere with the effectiveness of theses precesses.

• Sterilisation — Process used to destroy all microbial life.
  • Carried out in health-care facilities using physical and chemical methods.
  • The main methods include:
    • Steam under pressure
    • Dry heat 
    • EtO gas
    • Hydrogen peroxide gas plasma
    • Liquid chemicals
  • The picture to the right shows sterile medical instruments in heat-sealed packages. 

• Disinfection — Process which eliminates most // all pathogenic microorganisms, except for bacterial spores.
  • Objects for use in health-care are disinfected using liquid chemicals or wet pasteurisation.

• Germicide — Agent which can kill microorganisms — Particularly pathogenic organismsGermicides include both antiseptics & disinfectants.

• Antiseptic — Germicides which are applied to living tissues & skin.
  • Used for skin and not for surface disinfection.
  • An example of an antiseptic is TCP shown right

• Disinfectants — Germicides which are only applied to inanimate objects.
  • Application to the skin can cause damage.
  • An example of a disinfectant is Dettol shown to the right

• Critical items — Have a high risk for infection if contaminated with any microbes
  • Critical items include:
    • Surgical instruments 
    • Cardiac & urinary catheters 
    • Implants 
    • Ultrasound probes used in sterile body cavities 
  • Items in this category should either be purchased sterile or sterilised with steam.
  • If the objects are heat-sensitive other sterilisation methods such as Eto gas or Hydrogen peroxide gas plasma can be applied.

• Semi-critical items — Items which will come into contact with mucous membranes or non intact skin. 
  • These medical devices should be free from all microbes — Small numbers of bacterial spores are acceptable.
  • Semi-critical items require at least high-level disinfection using chemical disinfection.
  • In the image to the right are a few examples of semi-critical medical devices.

• Non-critical items — Items which will come into contact with the skin but not with mucous membranes.
  • The intact skin acts as an effective barrier against most microbes there sterility of these items isn’t critical.
  • Examples of non critical items include:
    • Bed pans
    • Blood pressure cuffs
    • Crutches
    • Computers
  • Most non-critical reusable items can be decontaminated where they are used.
  • Almost no risk has been associated with the transmission of infectious agents to patients via non-critical items.