Disinfection & Sterilisation (L19&20) Flashcards Preview

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Define disinfection

Process by which the number of microorganisms are reduced to a level that is considered safe

- some bacteria, spores & viruses remain


What does cleaning do? (x2)

1. Reduces the bioburden (e.g. blood/skin), making everything else more effective after that
2. Removes chemical traces


How to clean? (x3)

1. manual / automated machine
2. hot water and detergent, rinse thoroughly and dry
3. dry via disposable towels or automa


3 Sources of heat for disinfection

1. Pasteurisation at 63deg for 30min or 72deg for 20 min
2. Boiling water for 10min
3. Washing and rinsing from 70deg to 90 deg


What does ultrasound utilise and what are its functions?

utilise HIGH FREQUENCY SOUND WAVES; Remove dirt also disrupt cells, membranes. they are used in preparation of material prior to autoclaving (e.g. burs)


Compare between disinfectants and antiseptics

Both are chemical methods of disinfection.
Disinfectants are for use on inanimate objects while antiseptics are for use on living tissue


What can be used to reduce microbes on skin and mucous membranes? (X4)

1 Alcohols (70% isopropanol or 70% ethyl-alcohol)
2 Cetrimide ("Savlon")
3 Chlorhexidine (Bisguanides)
4 Iodine


Mode of action of alcohols (x5)

1. Requires wet contact for 3mins
2. Kills bacteria rapidly (30secs on dry surface)
3. Inactive against spores and fungi
4. Evaporates, flammable and inactivated by organic material
5. Used as skin antiseptic before injection


What can be used to reduce microbes on inanimate objects? (x3)

1 Hypochlorites (eg NaOCl)
2 Phenols
3 Alcohols


Briefly describe Cetrimide

It is a low level disinfectant made up of quaternary ammonium compounds, containing cationic surface active detergents.

It is inactivated by many substances including anionic detergents, soap and water.


How does the cationic surface active detergents help in reducing microbes?

Cationic charge is key to disruption of membrane because of the interaction with the phospholipid membrane, allowing it to interact/penetrate membrane.


Name two substances that inactivate staphylococci but are not so active against other bacteria

1. Chlorhexidine
2. Cetrimide


Hypochlorites are often used for impression disinfection. What solutions should be used for:
a) Impression with visible blood contamination
b) Impression without blood contamination

a) "Strong" hypochlorite 1% solution, expose for 2 mins
b) "Weak" hypochlorite 0.1 solution, expose for 10mins


Which disinfectant is effective for bacterial spores?



Define sterilisation

The process by which all micro-organisms are killed or removed to render the object incapable of causing infection


List 4 methods of sterilisation

1. Heat
2. Chemical
3. Radiation
4. Filtration


How does moist heat work?

It kills by coagulating and denaturing enzymes and structural proteins


Name 2 methods of chemical sterilisation

1. Formaldehyde vapour
2. 2% Gluteraldehyde


List the symptoms of vCJD (x7)

1. Average age 28
2. Progressive dementia
3. Sensory symptoms
4. Unsteadiness
5. Involuntary movements
6. Immobile and mute
7. Death in


Compare the variant CJD (vCJD) with sporadic CJD (sCJD) (x2)

1. Average age affected - 28 VS 65
2. Death in less than 14 months VS 4.5 months


Name a prion based disease

Creutzfeldt-Jakob disease (CJD) (a fatal human neurodegenerative condition)


How is CJD transmited

person-to-person spread by contaminated surgical instruments that have not been cleaned/disinfected