Microbiology: Disinfectants Flashcards by Rhiannon Price

How long do endospores of viruses and prions live in the environment for?

A very long time (years)

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How can we sterilise liquids?

Filtration
Heat inactivation (but this can caramelise sugars and degrade compounds)
Irradiation
Chemical (surface decontamination)

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How does an autoclave work?

Heats under pressure by steam to take the temperature above 120°C. It is held at temperature to ensure heat is distributed in samples. It kills 100% of bacteria viruses and parasites but may damage the sample.

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How does pasteurisation work?

Rapidly heating and then rapidly cooling the food

It is NOT sterilization and does NOT kill all micro-organisms in the food

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Why do we pasteurise instead of sterilise?

The process used as it has less effect on the quality of the foodstuff and it reduces the number of sensitive viable pathogens ca. 90% effective against vegetative bacteria (i.e. non sporulating bacteria)

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Define disinfection

destruction of micro organisms by physical or chemical methods on surfaces of objects.

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Define antisepsis

destruction of micro organisms on tissues by chemicals which are non toxic non irritating to the tissue.

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Are alcohol disinfectants affective against: 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
Coccidiosis (parasite) 
Prions

Mycoplasma: ++
Gram +ve: ++
Gram -ve: ++
Enveloped viruses: +

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Are acid disinfectants affective against: Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
Coccidiosis (parasite) 
Prions

Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses

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Are alkali disinfectants affective against: Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
Coccidiosis (parasite) 
Prions

Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses +/-
Fungal spores 
Acid fast bacteria 
Bacterial spores +/-
Coccidiosis (parasite)

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Are aldehyde disinfectants affective against: 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
Coccidiosis (parasite) 
Prions

Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores

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Are biguanide disinfectants affective against: 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
Coccidiosis (parasite) 
Prions

Mycoplasma
Gram +ve
Gram -ve

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Are quaternary ammonium disinfectants affective against: 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
Coccidiosis (parasite) 
Prions

Mycoplasma
Gram +ve
Gram -ve

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Are phenolic disinfectants affective against: 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
Coccidiosis (parasite) 
Prions

Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses +/-
Fungal spores 
Bacterial spores
Coccidiosis (parasite)

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Are oxidising agent disinfectants affective against: 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
Coccidiosis (parasite) 
Prions

Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores

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Are halogen compound disinfectants affective against: 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
Coccidiosis (parasite) 
Prions

Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores

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How do alcohol disinfectants work?

Denature proteins causing membrane damage

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Wha are the advantages and disadvantages of alcohol disinfectants?

D: They’re flammable, limited activity in the presence of organic material, can damage rubber/plastics
A: Evaporates quickly and leaves no residue

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How do acid disinfectants work?

Low ph inhibits growth by destroying proteins and enzymes

Can HCl destroy endospores

Yes

What are the problems with acid disinfectants?

They can be caustic/toxic at high conc

Reactive and can damage surfaces

How do alkali disinfectants work?

By saponifying liquids within cell membranes

Activity increases with raised temp

What are the most common alkali disinfectants?

Sodium and potassium hydroxides
Ammonium hydroxide
Sodium carbonate
Calcium oxide

What are some of the problems with alkali disinfectants?

Can burn and cause corrosion

Some react violently to water

How do aldehyde disinfectants work?

Denature proteins and are highly reactive (= highly effective)

What are the main aldehyde disinfectants?

Formaldehyde (works against parasites) | Glutaraldehyde

What are the problems with aldehyde disinfectants?

Highly toxic, irritating and carcinogenic

What is chlorhexidine and what is it used for?

Alcohol based Chlorhexidine wide use for hand washing and pre-op skin preparation More active against gram +ve than -ve

What are some problems with biguanides?

Limited effectiveness against acid fast bacteria, fungi viruses and spores limited pH range

How do chlorine compound detergents work?

electronegative denaturing of proteins

What is the most commonly used chlorine compound disinfectant?

Sodium hypochlorite

What are the problems with iodine compounds?

High concentrations can be irritating Stain everything Poor stability and inactivated by organic material Low solubility so often dissolved in ethyl alcohol

What are iodophors?

More stable iodine compounds that have a sustained release of iodine The dilution of iodophors increases the free iodine activity

Do phenolic compounds work with organic material?

Yes and in hard water | %% solutions are considered bactericidal

What are the problems with phenolic compounds?

Can cause irritation Environmental concerns being phased out ] can taint food so not used in food industry Concentrations over 2% toxic, esp to cats

How do QAC's work?

They are cationic detergents so attack the negative charges on the surface of microorganisms and irreversibly bind phospholipids and proteins effecting cell permeability

What are the problems with QAC's?

Only really active against mycoplasmas and bacteria Easily inactivated by organic debris and hard water and detergents Toxic to fish

What is the most common QAC?

Benzalkonium

How do oxygen compounds work?

Peroxide based they denature proteins and lipids

What are the main oxygen compound disinfectants?

Peroxide Virkon ozone peracetic acid

What conc peroxide is needed to be bactericidal/virucidal/fungicidal?

5-20% | 30% is sporicidal

What is per acetic acid?

A formulation of hydrogen peroxide and acetic acid | has some activity in organic acid

What is virkon?

Potassium peroxymonosulphate an sodium chloride | Some activity in the presence of organic material

What can peroxide vapour replace?

Formaldehyde

where is ozone used?

Water systems for feeders