Sterilisation and disinfection Flashcards
What is disinfection?
The destruction or removal of all or nearly all pathogens, but not all microorganisms
This 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 microorganisms
This 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 again
Not 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
- critical risk:
- Procedure Type (use characteristics): Percutaneous entry into tissue, body cavity or vascular system (surgical access)
- Level of Decontamination Required: Preoperative instrument sterility required - Semi critical:
- Procedure Type (use characteristics): Surface contact with diseased or non-intact skin or with mucous membranes
-Level of Decontamination Required: Sterilisation preferred but minimum of preoperative disinfection required if sterilisation not possible - Non-critical:
-Procedure Type (use characteristics): Contact with healthy intact skin
-Level of Decontamination Required: Disinfection preferred as a minimum. Item visibly cleaned by standardised process
Can light guns be sterilised?
No- so it needs to be barrier wrapped
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?
- Infectious agent: bacteria, viruses, fungi, protozoa, helminths etc.
- Reservoir: people, equipment, water
- Portals of exit: excretions, secretions, droplets, skin
- Means of transmission: direct contact/fomites, injection/ingestion, airborne, aerosols
- Portal of entry: broken skin, mucous membrane, gastrointestinal/respiratory/urinary tract
- Susceptible host: neonates, diabetics, immunosuppressed, cardio pulmonary disease
slide 15
What types of infectious agents are transmissible during healthcare procedures?
Bacteria (MRSA, MSSA, etc.)
Viruses (HBV, HCV, HIV, etc.)
Fungi (C. alb)
Prions (vCJD)
Protozoa
Helminths
What can act as a microorganism ‘reservoir’?
areas where microorganisms can reside and proliferate - within people, environments, instruments and equipment
Non porous-load ‘solid’ instruments (scaler)
Porous-load instruments & equipment
look at slide 19
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?
- use
- transport
- clean
- disinfect
- inspection
- package
- sterilisation
- transport
- store
What are the modifying factors for effective disinfection & sterilisation?
Nature of microorganisms: virus vs spores
Level of contamination: bio-load
Environmental conditions: moisture, temperature
Nature of equipment to be decontaminated: material, complexity
E.g. the 3 in 1 can’t be sterilised so it has to be barrier-covered
what are the 4 cycle stages of automatic washer-disinfectors?
- Cool rinse at 35 degrees
2.Hot wash at 55 degrees
3.Thermal disinfect at 93 degrees
4.Forced air-drying
slide
How efficient are automatic washer-disinfectors?
Manual cleaning: 35% efficiency
Ultrasonic cleaner: 55% efficiency
Domestic dishwasher: 70% efficiency
Medical washer disinfector: 95%+ efficiency
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 134-137 degrees or else it would damage instrument
Time = 3 mins needed for sterilisation at 134-137 degrees but 18 mins at 121 degrees
Pressure = 2.2-2.5 bar
slide 37
What are the different autoclave steriliser types?
N type
B type
S type
what is an n type Autoclave Sterilizer?
AKA: non-vacuum, downward displacement
Used for solid, non-porous and unwrapped, un-pouched instruments only
what is a b type Autoclave Sterilizer?
AKA: Vacuum, forced air removal
Used for wrapped, pouched, porous (air-retentive) materials and instruments
what is a s type Autoclave Sterilizer?
Special autoclaves for specific decontamination purposes e.g. endoscopes & dental hand piece sterilisation
