M18 - Disinfection and sterilization Flashcards
(32 cards)
what is the definition of disinfection?
Process by which the number of microorganisms are reduced to a level that is considered safe
what is an antiseptic?
antimicrobial agent that can be applied safely to the surface of the body or exposed tissues
Describe the cleaning involved in disinfection.
– Reduce the bioburden (organic material, living & dead)
– Manual or automated
– Hot water & detergent, rinse thoroughly & dry
- improve success of downstream disinfection and sterilisation
(removing anything that complicates the disinfection process)
Describe the heat involved in disinfection.
– a) Pasteurisation 63 ̊C 30 mins or 72 ̊C for 20 minutes
– b) Boiling Water 10 mins
– c) Washing & Rinsing 70 ̊C to 90 ̊C
(using heat to disrupt molecules)
Describe the ultrasound involved in disinfection.
– a) high frequency sound waves
– b) remove dirt also disrupt cells, membranes.
– c) used in preparation of material prior to autoclaving
Describe the chemicals involved in disinfection.
– Disinfectants - for inanimate objects
– Antiseptics - for living tissue
Describe the action of alcohol’s in reducing microbes on skin and mucous membranes.
– Not pure i.e. 70%
– Requires wet contact for 3 minutes
– Kill bacteria rapidly (30 secs on dry surface)
– Inactive against spores & some fungi, expensive
– Evaporates, flammable & inactivated by organic material
– Skin antiseptic before injection
Describe the action of cetrimide (savlon) in reducing microbes on skin and mucous membranes.
– Low level disinfectant
– Quaternary ammonium compounds
– cationic surface active detergents
– denature membranes
– effective cleansing agent
– inactivated by many substances including anionic detergents, soap and water
( i.e disruption of bacterial membranes using charged molecules )
Describe the action of Chlorhexidine in reducing microbes on skin and mucous membranes.
– Non toxic to skin and mucous membranes
– Inactivates Staphylococci,not so active against other bacteria
– Readily inactivated
– Mouthwash (problem;taste and toothstaining)
– Hibitane skin disinfectant
– Hibiscrub hand disinfectant
-Hibisol rapid drying hand disinfectant (alcohol&detergent)
Describe the action of Iodine in reducing microbes on skin and mucous membranes.
– Betadine (surgical scrub e.g. hebiscrub allergy)
– Very active against wide spectrum of bacteria
– Some activity against spores, fungi & viruses
– Inactivated by organic material
– Can cause skin reaction & stain skin
– Iodophors (combination of iodine & detergent)
– 2.5% Iodine in water or alcohol, 2 mins, excellent skin antiseptic
Describe hypochlorites action in reducing microbes on inanimate objects.
– Strong hypochlorite 1% solution;
• for impression disinfection with visible blood contamination
expose for 2 mins
• spills of vomit, sputum, blood, leave for 10-20mins & wash with detergent.
– Weak hypochlorite 0.1% solution
• for impression disinfection with no blood contamination expose
for 10 mins
• General environment disinfectant (e.g. floors, walls, toilets)
Describe phenols action in reducing microbes on inanimate objects.
- Denature proteins and disrupt cell membranes
- Hycolin 1%
- Used for spills of difficult materials e.g faeces
- Can be used with detergents without loss of activity
Describe alcohols action in reducing microbes on inanimate objects.
– Surface cleaner, dental chair, work surface
– Bactericidal, vegetative bacteria, TB, fungi & viruses
– Do not inactivate spores
– Denaturation of protein & membrane disruption
– Evaporates; so short term disinfection
what is considered when using disinfectants?
• Is disinfection required? –What level/type of contamination ,future use of material • Spectrum – Range of antimicrobial activity • Rate of action – Length of exposure – Number of Organisms (type) – Temperature – Dilution/Volume – Presence of Organic matter • Type of action – Bacteriocidal – Bacteriostatic • Effect of pH. – Phenols must be at the correct pH for activity • Stability – should be made fresh – used material discarded • Contact time
What is the definition of sterilisation?
the process by which all infectious organisms are killed or removed to render the object incapable of causing infection
what is the medical definition of sterilisation?
one in a million instruments has one bacteria
what are the methods of sterilisation?
- Heat (autoclave)
- Chemical
- Radiation (gamma -irradiation)
- Filtration
what is considered when choosing the type of sterilisation?
– Purpose – Nature of material – Nature of Contamination – Convenience (time)
In pattern of microbial death , what is the D Value?
– decimal reduction time
“time taken to reduce the viable number of organisms by 90%”
what is the bioburden?
number of bacteria present
what is the nature of sterilisation media?
proteinaceous organic material increase chance of survival
Describe sterilisation by DIRECT heat.
– Heating metal object to white hot
– Flaming a metal loop or forceps in bunsen
– Incineration of combustible waste
Describe sterilisation by DRY heat.
– Kills by destructive oxidation of essential cell constituents.
– Hot air oven
– Article placed in container
– Efficiency linked to temperature & time
– 160 ̊C for 120 mins, 180 ̊C for 30 mins
– e.g. metal instruments, mirrors, burs, files, reamers, glassware
Describe sterilisation by MOIST heat.
Kills by coagulating & denaturing enzymes & structural
proteins
– Steam, steamer or boiling water bath 100 ̊C for 30mins – Autoclaving (quick & reliable)
• Principle at higher temperatures than >100 ̊C water boils
• Closed vessel, steam pressure rises, temperature rises.
• Higher pressure, higher temperature & shorter time.
