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3151 - nat > Disinfectants, Biofilms > Flashcards

Disinfectants, Biofilms Flashcards

1
Q

Sterilisation VS Disinfection

A

Sterilisation: Eliminate all forms of microbial life

Disinfection: Eliminates all forms of microbial life except bacterial spores

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2
Q

Alcohol MOA, Activity increased by?
Disadvantages

A

MOA: denatures proteins on membrane, activity increased by water

Disadv: Not sporicidal, activity affected by organic matter, volatile

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3
Q

2 Examples of alcohol disinfectants

Which is more efficacious for lipophilic virus?

A

Isopropyl alcohol
Ethanol

Isopropyl alcohol is more lipophilic, more efficacious against lipophilic virus

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4
Q

Optimal concentration of alcohol

A

60-90%

significantly lower activity below 50%

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5
Q

Ammonia MOA, Uses, Caution, Examples

A

MOA: saponify lipids in envelope of microbes
General purpose cleaner, used for glass and stainless steel
Caution: irritant to eyes, do not mix with bleach

Example: Aq Ammonia, Ammonia Hydroxide

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6
Q

4 Examples of Aldehydes

A

Formaldehyde
Paraformaldehyde
Glutaraldehyde
Ortho-phthalaldehyde (OPA)

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7
Q

MOA of Aldehydes

Adv

Disadvantages

Uses or Forms

A

Alkylation of functional groups (SH, OH, C=O, NH), altering RNA, DNA, protein synthesis

Adv: Broad spectrum of activity, sporicidal

Disadvantage: Toxic, Odour

Uses or Forms: Liquid (eg. in anat hall), Gas (vapour phase sterilant)

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8
Q

Adv and Disadv of OPA

Difference between OPA and aldehydes in general

A

Stable over wide range of pH 3-9
Stains proteins gray

Not irritating to eye and nasal passages, no odour (aldehydes generally toxic and have odour)

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9
Q

2 Examples of biguanides

A

Chlorhexidine, Alexidine

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10
Q

Characteristics of Chlorhexidine
What is Chlorhexidine activity affected by?

A

Broad spectrum bactericidal agent
Activity affected by pH and organic matter

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11
Q

Which is more effective, Alexidine or Chlorhexidine. Why?

A

Alexidine has faster onset of bactericidal activity and produces faster alteration in bacterial permeability

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12
Q

Characteristics of Chlorine (Sodium Hypochlorite)
What can it be used on?
Spectrum of activity
Affected by what?

A

Broad spectrum
Toxic but volatile
Able to remove biofilm
Affected by pH (due to dissociation of active HOCl) and organic matter
Not affected by water hardness

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13
Q

MOA of Sodium Hypochlorite

Caution for Sodium Hypochlorite
Which surface should it not be used on?

A

Undissociated HOCl

Do not mix with Ammonia, will release toxic chlorine gas
Corrosive to metals

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14
Q

Why is Sodium Dichloroisocyanurate (NaDCC) tablet more effective and have prolonged bactericidal effect than Sodium Hypochlorite (HOCl)?

A

When monochloro releases chlorine, dichloro can release its chlorine to restore more monochloro in the equilibrium. Whereas Hypochlorite can only one chlorine atom per HOCL molecule.

Overall, NaDCC has more chlorine atoms to release than Sodium Hypochlorite, hence have prolonged bactericidal effect.

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15
Q

MOA of Iodine

A

Disrupt protein, nucleic acid structure and synthesis

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16
Q

How does dilution increase Povidone-Iodine activity?

A

Dilution weakens iodine linkage to carrier polymer, increasing free iodine in solution

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17
Q

Definition of iodophor

A

Combination of iodine and solubilizing agent

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18
Q

Uses of Iodophor vs Iodine
Benefits of Iodophor over iodine

A

Uses:
Iodophor: Disinfectant and antiseptic
Iodine: Antiseptic only

Benefits
Iodophor: Non staining, not toxic or irritant
Iodine: Bad smell, staining

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19
Q

MOA of H2O2

Advantage of H2O2

Disadvantage of H2O2

A

H2O2 acts as oxidising agent, produce free radicals OH that attack essential cell components

Advantage:
Sporicidal at high conc
Can be used as vapour phase sterilant
Environmentally friendly (broken down to H2O and O2)

Disadvantage:
Targeted by catalase and peroxidases

20
Q

3 components of Accelerated Hydrogen Peroxide, how do they help H2O2 and what is it used for?

A

Enhanced H2O2,
contains
1) surfactant
2) organic acid (to remove ions)
3) emulsifier

Used to stabilise H2O2, used on medical devices

21
Q

Reasons why Peracetic acid is more effective than Hydrogen peroxide

A
  1. More potent (but more toxic)
  2. Need lower conc to be sporicidal
  3. Not decomposed by peroxidases or catalase
22
Q

What is Peracetic acid used for

A

Low temperature liquid sterilant for medical devices, flexible scopes, hemodialyzers, environmental surface sterilant

23
Q

3 Examples of phenols

A

Phenol, Cresol, Chloroxylenol

24
Q

MOA of Phenol

A

Induce leakage of cellular components

25
Q

MOA of Chloroxylenol

A

Disrupt microbial cell wall → Inactivation of cellular enzymes

26
Q

2 Examples of Diamidine

A

Propamidine and Dibromopropamidine

27
Q

What are diamidines used for

A

antiseptic for wound

28
Q

MOA of Propamidine

A

Inhibit oxygen uptake and leakage of amino acids

29
Q

Examples of Silver compounds (5 pts)

A

Silver sulfadiazine
Silver
Silver acetate
Silver nitrate
Silver protein

30
Q

MOA of Silver Sulfadiazine

A

Induce membrane blebs

31
Q

Why is Mercuric Chloride toxic?

A

Corrosive
Accumulate in kidneys, causing severe damage leading to acute kidney failure

32
Q

What is another name for QAC

A

Cationic detergents

33
Q

3 uses of QAC

A

Preoperative disinfection of unbroken skin
Application to mucous membrane
Disinfection of noncritical surfaces (walls, furniture, floors)

34
Q

MOA of QAC

A

1) Adsorption and penetrate cell wall
2) React with cytoplasmic membrane
3) Leakage of intracellular low MW material
4) Degradation of proteins and nucleic acids
5) Wall lysis caused by autolytic enzymes

35
Q

Spectrum of activity of QAC

What kind of virus does it work on, not work on?

A

Fungicidal
Bactericidal
Virucidal against enveloped (lipophilic) virus

Not sporicidal
Not tuberculocidal
Not virucidal against non enveloped (hydrophilic) virus

36
Q

What are vapour phase sterilants used for?

A

Disinfection of heat-sensitive medical devices and surgical supplies

37
Q

4 examples of vapour phase sterilants

A

Ethylene oxide
Formaldehyde
H2O2
Peracetic acid

38
Q

Four resistant mechanisms of biofilms

A

Layers of old biofilms
Genotypic variation
Production of neutralising enzymes
Physiologic environment within biofilm eg. pH

39
Q

Benefits of vapour phase sterilants

A

1) Increase contact time for volatile liquid disinfectants eg. Chlorides
2) Disinfect heat sensitive equipment

40
Q

Sporicidal (4 points)

A
  • Chlorine (Sodium hypochlorite)
  • Aldehyde (at high conc)
  • H2O2 (higher conc)
  • Peracetic acid (low conc)
41
Q

Oxidising agents (4 points)

A
  • Peracetic acid
  • Hydrogen peroxide
  • Sodium Hypochlorite
  • Ozone
42
Q

Affected by organic matter (3 pts)

A
  • Alcohol
  • Biguanides
  • Sodium hypochlorite
43
Q

Toxic (4 pts)

A
  • Chlorine
    o Esophageal burns, ocular irritation, gastric burns
  • Aldehyde
  • Ammonia (but volatile)
  • Mercuric chloride
    o Corrosive, accumulate in kidneys, lead to kidney failure
44
Q

Dependent on pH (6 pts)

A
  • Chlorhexidine
  • Sodium hypochlorite
    o Effective at lower pH, undissociated HOCl
  • Iodine
  • Phenols
  • Aldehyde
  • QAC
45
Q

Vapour phase sterilants

A
  • Ethylene oxide
  • Formaldehyde
  • H2O2
  • Peracetic acid
46
Q

Can use on medical devices

A
  • Accelerated H2O2
  • Peracetic acid
  • Silver compounds
  • Vapour phase sterilants
47
Q

What can remove biofilms (2 points)

A

Chlorine (eg. in pools)
Ozone

3151 - nat (22 decks)

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