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PVS > Microbiology: Disinfectants > Flashcards

Microbiology: Disinfectants Flashcards

1
Q

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

A

A very long time (years)

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2
Q

How can we sterilise liquids?

A

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

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3
Q

How does an autoclave work?

A

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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4
Q

How does pasteurisation work?

A

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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5
Q

Why do we pasteurise instead of sterilise?

A

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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6
Q

Define disinfection

A

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

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7
Q

Define antisepsis

A

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

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8
Q 
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
A

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

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9
Q 
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
A

Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses

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10
Q 
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
A 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses +/-
Fungal spores 
Acid fast bacteria 
Bacterial spores +/-
Coccidiosis (parasite)
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11
Q 
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
A 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
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12
Q 
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
A

Mycoplasma
Gram +ve
Gram -ve

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13
Q 
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
A

Mycoplasma
Gram +ve
Gram -ve

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14
Q 
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
A 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses +/-
Fungal spores 
Bacterial spores
Coccidiosis (parasite)
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15
Q 
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
A 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
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16
Q 
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
A 
Mycoplasma
Gram +ve
Gram -ve
Enveloped viruses 
Non-enveloped viruses
Fungal spores 
Acid fast bacteria 
Bacterial spores
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17
Q

How do alcohol disinfectants work?

A

Denature proteins causing membrane damage

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18
Q

Wha are the advantages and disadvantages of alcohol disinfectants?

A

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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19
Q

How do acid disinfectants work?

A

Low ph inhibits growth by destroying proteins and enzymes

20
Q

Can HCl destroy endospores

A

Yes

21
Q

What are the problems with acid disinfectants?

A

They can be caustic/toxic at high conc

Reactive and can damage surfaces

22
Q

How do alkali disinfectants work?

A

By saponifying liquids within cell membranes

Activity increases with raised temp

23
Q

What are the most common alkali disinfectants?

A

Sodium and potassium hydroxides
Ammonium hydroxide
Sodium carbonate
Calcium oxide

24
Q

What are some of the problems with alkali disinfectants?

A

Can burn and cause corrosion

Some react violently to water

25
Q

How do aldehyde disinfectants work?

A

Denature proteins and are highly reactive (= highly effective)

26
Q

What are the main aldehyde disinfectants?

A

Formaldehyde (works against parasites)

Glutaraldehyde

27
Q

What are the problems with aldehyde disinfectants?

A

Highly toxic, irritating and carcinogenic

28
Q

What is chlorhexidine and what is it used for?

A

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

29
Q

What are some problems with biguanides?

A

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

30
Q

How do chlorine compound detergents work?

A

electronegative denaturing of proteins

31
Q

What is the most commonly used chlorine compound disinfectant?

A

Sodium hypochlorite

32
Q

What are the problems with iodine compounds?

A

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

33
Q

What are iodophors?

A

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

34
Q

Do phenolic compounds work with organic material?

A

Yes and in hard water

%% solutions are considered bactericidal

35
Q

What are the problems with phenolic compounds?

A

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

36
Q

How do QAC’s work?

A

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

37
Q

What are the problems with QAC’s?

A

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

38
Q

What is the most common QAC?

A

Benzalkonium

39
Q

How do oxygen compounds work?

A

Peroxide based they denature proteins and lipids

40
Q

What are the main oxygen compound disinfectants?

A

Peroxide
Virkon
ozone
peracetic acid

41
Q

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

A

5-20%

30% is sporicidal

42
Q

What is per acetic acid?

A

A formulation of hydrogen peroxide and acetic acid

has some activity in organic acid

43
Q

What is virkon?

A

Potassium peroxymonosulphate an sodium chloride

Some activity in the presence of organic material

44
Q

What can peroxide vapour replace?

A

Formaldehyde

45
Q

where is ozone used?

A

Water systems for feeders

PVS (43 decks)

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