Sterilisation & Disinfection

• What is disinfection?

  The destruction or removal of all or nearly all pathogens, but not all microorganismsThis process may not be absolute & may result in only a reduction in the number of potentially harmful microorganisms
• What is sterilisation?

  The destruction or removal of all microorganismsThis is an ‘absolute’ & at the end of a sterilisation process, no viable microorganisms are present
• What is decontamination?

  Decontamination is a combination of processes carried out to render a contaminated reusable medical device safe to use againNot a sterility absolute; it depends upon the nature of the equipment & the use characteristics for the types of procedure for which they are required
• How are decontamination requirements classified?

  By procedure risk

  
• Can light guns be sterilised?

  No
• What is cross-infection?

  The transmission of a microorganism (infection) from one place/person to another in the same healthcare environment
• What does the cycle of infection look like?

  
• What types of infectious agents are transmissible during healthcare procedures?

  Bacteria (MRSA, MSSA, etc.)Viruses (HBV, HCV, HIV, etc.)Fungi (C. alb)Prions (vCJD)ProtozoaHelminths
• What can act as a microorganism 'reservoir'?

  cfu= colony forming unit

  
• What is the commonest & most important area of cross contamination?

  Our hands
• How do microorganisms get from the instruments that we use into the patient?

  Aerosol, inject, splatter, contact

  Everything must be sterile!
• What are the mechanisms of cross contamination (infection)?

  Direct contact: infectious agent transmission from same or different person

  Indirect contact: via instruments or equipment

  Inhaled/airborne: DUWL's, sneezing, coughing, etc.

  Ingested: food & water hygiene

  Vector: clothing, towels, insects, animal contact, etc.
• What are the different portal of entry for the microorganisms?

  Gingival margin, possible cavities, surgical wounds, area of infection, area of non intact mucosal skin, area of non healing bone, etc.
• How are medical devices decontaminated?

  Disinfected by chemical, mechanical or thermal means

  Sterilised by either irradiation, chemical or thermal means
• What does the decontamination cycle look like?

  
• What are the modifying factors for effective disinfection & sterilisation?

  Nature of microorganisms: virus vs sporesLevel of contamination: bio-loadEnvironmental conditions: moisture, temperatureNature of equipment to be decontaminated: material, complexityE.g. the 3 in 1 can't be sterilised so it has to be barrier-covered
• How efficient are automatic washer-disinfectors & what are the 4 cycle stages?

  
• What are the different types of irradiation?

  Non-ionising: UV light

  Ionising: X-rays, gamma rays, electron beams
• What different chemical sterilisation methods are used?

  Liquid: glutaraldehyde, formaldehyde, hydrogen peroxide, paracetic acid

  Gas: ethylene oxide, nitrogen dioxide, ozone
• How do you thermally sterilise?

  Direct heat: instrument 'flaming', incineration

  Indirect heat: particulate= glass bead, dry= hot air 'oven', moist= steam 'autoclave
• What are the parameters for autoclave sterilisation?

  Temp. no higher than this or else it would damage instrument

  
• What are the different autoclave steriliser types?