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IC6 Disinfectants Flashcards

1
Q

Factors that affect efficacy of both disinfection and sterilisation (12)

A
  • Prior cleaning of object (most important)
  • Organic and inorganic load present
  • Type and level of microbial contamination
  • Exposure time to germicide
  • Physical nature of object eg crevices, hinges, lumens
  • Presence of biofilms
  • Temperature and pH of disinfection process
  • Number of microbes
  • Innate resistance of microorganisms
  • Concentration and potency of disinfectants
  • Humidity
  • Water hardness
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2
Q

Definition of sterilisation

A

Process that destroys or eliminates all forms of microbial life and is carried out in health care facilities by physical or chemical methods

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3
Q

Definition of disinfection

A

Process that eliminates many or all pathogenic microorganisms, except bacterial spores, on inanimate objects

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4
Q

Name the 4 most common vapour phase sterilants

A

1) ethylene oxide
2) formaldehyde
3) hydrogen peroxide
4) peracetic acid

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5
Q

What is the advantage of formaldehyde gas over ethylene oxide gas?

A

Non-explosive

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6
Q

What is the MOA of ethylene oxide and formaldehyde

A

They are broad-spectrum alkylating agents and they attack proteins, nucleic acids and other organic compounds; both are particularly reactive with sulfhydryl and other enzyme reactive groups

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7
Q

Name 2 disadvantages of using Ethylene oxide gas.

A

Mutagenic and explosive

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8
Q

Name the chemical disinfectants (16)

A
  • Alcohol
  • Ammonia
  • Chlorine containing compounds
  • QAC
  • Aldehyde & Ortho phthalaldehyde OPA
  • Biguanide
  • Iodine and iodophors
  • Peroxygen & Accelerated H2O2
  • Peracetic acid
  • Phenols
  • Diamidines
  • Silver compounds
  • Chloroxylenol
  • Mercuric chloride
  • Benzalkonium chloride
  • Vapour phase sterilants
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9
Q

MOA of UV lamps

A

Short wavelength UV light use to kill or inactivate microorganisms by destroying nucleic acids and disrupting DNA

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10
Q

Uses of UV lamps (2)

A
  • Supplement current hospital or laboratories cleaning and disinfection of contaminated surfaces
  • Recently used for water treatment (usually coupled with ion sequestration and chlorine disinfection)
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11
Q

Factors affecting effectiveness of UV lamps

A
  • Exposure time
  • Intensity and wavelength of UV radiation
  • Presence of interfering particles
  • Microorganism’s UV innate resistance
  • Line-of-sight exposure of microorganisms to UV light
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12
Q

Uses of alcohol (3)

A
  • Hard surface disinfection and skin antisepsis, especially coupled with other excipients or other biocides
  • Preservation
  • Kill bacteria, virus, fungi (no spores)
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13
Q

What are some excipients used to enhance disinfectant activity and how do they enhance activity?

A

1) Emollient; makes the skin softer and allow for easier entry into 1st layer of skin and not just the surface

2) Surfactants; disrupt the outer layer of the bacteria and make them more sensitive to the disinfectant

3) Chelating agents; protects the disinfectant by complexing with metal ions

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14
Q

MOA of alcohol

A
  • Inhibition of the production of metabolites essential for rapid cell division (bacteriostatic)
  • Denaturation of proteins and this mechanism is increased by water
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15
Q

What is the MOA of ammonia

A

It works by saponifying lipids within the envelopes of microorganisms (affects lipids in outer membrane by complexing them and making them precipitate)

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16
Q

What is ammonia used for?

A

General purpose cleaner for many surfaces like glass and stainless steel (disinfectant)

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17
Q

Comment on the safety of ammonia

A

Irritant for the eyes and the gastric system (should not be ingested); if mixed with bleach, it may release chloramine which is toxic

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18
Q

Comment on the activity of aldehydes

A

Broad spectrum; Can kill spores, bacteria, fungi and viruses

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19
Q

What is the MOA of aldehydes

A

Biocidal activity of results from alkylation of sulfhydryl, hydroxyl, carboxyl and amino groups of microorganisms, which alters RNA, DNA and protein synthesis.
(RNA and DNA not as affected as much compared to protein synthesis as they need sulfhydryl groups to work, which is found in amino acid)

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20
Q

Name the disadvantages/ concerns of using aldehydes

A

Toxicity and their odor.

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21
Q

Name the advantages of OPA over aldehydes (formaldehyde and glutaraldehyde) and its limitations

A

Advantages:
1) More lipophilic compared to formaldehyde and glutaraldehyde and can be absorbed more effectively.

2) Not a known irritant to the eyes and nasal passages, barely no perceptible odor

Disadvantages:
Stains protein grey (including unprotected skin)

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22
Q

What are aldehydes used for?

A

Disinfectant, Preservation, antisepsis (not really)

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23
Q

MOA of biguanides

A

Chlorhexidine: damage membrane. Cross cell outer membrane by passive diffusion. Attacks bacterial cytoplasmic (coagulation or gelling) or inner membrane or yeast plasma membrane

Alexidine: lipid phase separation. Apoptosis via destruction of bacterial membrane

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24
Q

Chlorhexidine VS alexidine

A

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

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25
Chlorine MOA
Largely attributed to undissociated hypochlorous acid (HOCl). - Oxidation of sulfhydryl enzymes & aa. - Ring chlorination of aa. - Inhibition of protein synthesis. - DNA disruption. - Loss of intracellular contents
26
List the strengths of chlorine. (6)
- Broad spectrum - Cheap - Fast acting - Unaffected by water hardness - Remove dried or fixed organisms and biofilms from surfaces - Low incidence of serious toxicity (No toxic residues)
27
List the weaknesses of chlorine (5).
- Ocular irritation - Burns (mouth, throat, stomach) - Corrosiveness to metals in high concentrations - Inactivation by organic matter - Release of toxic chlorine gas
28
chlorine uses (3)
disinfectant, cleaning, antisepsis
29
Comment on the spectrum of activity of Iodine/Iodophors
Broad spectrum of activity against bacteria, virus, fungi.
30
Name the uses of Iodine and Iodophors
Iodine: antiseptics on skin or live tissue Iodophors: antiseptics and disinfectants
31
What is an Iodophor?
Iodophor is a combination of iodine and a solubilizing agent or carrier; the resulting complex provides a sustained release reservoir of iodine and releases small amounts of free iodine in aqueous solution.
32
What are the advantages of using Sodium dichloroisocyanurate tablets
Stable, long release, microbial activity greater
32
Peroxygens uses (3)
Disinfection, sterilisation, antisepsis
33
Explain the MOA of Iodine/Iodophors
Penetrates the cell wall of microorganisms quickly and leads to disruption of protein and nucleic acid structure and synthesis
34
Peroxygen MOA
H2O2 acts as an oxidant by producing hydroxyl free radicals (*OH) which attack essential cell components, including lipids, proteins and DNA
35
Spectrum of activity of peroxygens
- Broad-spectrum biocide (bacteria, viruses, fungi, spores) - Greater activity in gram +ve. - Sporicidal at high concentration & long contact time
36
What is the difference between accelerated H2O2 and normal H2O2
Accelerated H2O2 is a disinfectant/ cleaning agent that uses excipients to stabilise H2O2 so that it can be used for extended periods of time, usually on medical or veterinary devices
37
Are iodophors more rapidly bactericidal when concentrated or diluted? Why?
Diluted. Dilution of povidone iodine might weaken the iodine linkage to the carrier polymer leading to increase of free iodine in solution.
38
Comment on the spectrum of activity of Paracetic acid (with relation to H202)
More potent than hydrogen peroxide, being sporicidal, bactericidal, virucidal and fungicidal at low concentrations (0.3%)
39
Weaknesses of accelerated H2O2 (2)
- Relatively short shelf life - Irritant to eyes
40
Name the uses for paracetic acid
Low-temperature liquid sterilant for medical devices and environmental surface sterilant
41
What excicipents may be present in accelerated H2O2 that increases its efficacy compared to normal H2O2?
1) Surfactant eg alkali metal and ammonium salts 2) Organic acid as a chelating agent eg phosphoric acid 3) Emulsifier eg alkylated diphenyl oxide
42
What is the MOA of Paracetic acid?
Similar to H2O2, peracetic acid is an oxidant and denatures proteins and enzymes and increases cell wall permeability by disrupting sulfhydryl (-SH) and sulfur (S-S) bonds.
43
Phenol uses (3)
- Antiseptic, disinfectant or preservative - Possesses antifungal (damage to plasma membrane) and some antiviral properties
44
Phenol MOA
induces progressive leakage of intracellular constituents, including release of K+, which it usually is the first index of membrane damage
45
Chloroxylenol MOA
disruption of microbial cell walls and inactivation of cellular enzymes
46
Chloroxylenol strength (1)
Relatively non toxic and non irritant material when used as an excipient in topical products
47
Name the added advantages of Paracetic acid over H2O2
1) Free from decomposition by peroxidases 2) Remains active in the presence of organic loads. 3) Not irritant at low concentrations and temperatures except for mild smell
48
Chloroxylenol weakness (1)
toxic upon oral consumption or eye contact
49
Diamidines uses (2)
Antisepsis, disinfection against growth of bacteria (bacteriostatic) esp wounds
50
Diamidines MOA
inhibition of oxygen uptake and leakage of aa
51
Chloroxylenol uses (3)
Antiseptic, antimicrobial, disinfectant
52
Silver compounds uses
Treatment of burns
53
Silver sulfadiazine VS silver nitrate
silver sulfadiazine is newer and has broader spectrum of activity than silver nitrate for bacteria
54
Silver nitrate MOA
interact with thiol groups in enzymes and proteins affecting microbial plasma, cytoplasmic membrane and nucleic acids. also for fungus
55
Comment on the spectrum of activity of mercuric chloride
Broad range disinfectant
56
What is the MOA of mercuric chloride?
affects microbial peptide synthesis
57
Quaternary ammonium compounds uses (3)
- Disinfectant (e.g. preoperative disinfection of unbroken skin) - Antimicrobial preservative (in pharmaceutical products for application to mucous membranes) - Disinfection of non critical surfaces eg floor, furniture, wall esp against fungus, bacteria, lipophilic (enveloped) virus (not sporicidal)
58
Quaternary ammonium compound MOA
- Adsorption and penetration of agent into cell wall - Reaction with cytoplasmic membrane (lipid or protein) followed by membrane disorganisation - Leakage of intracellular low molecular weight material - Degradation of proteins and nucleic acids - Wall lysis caused by autolytic enzymes
59
How is Eucalyptus essential oil produced?
Steam distillation
60
What is Eucalptus essential oil used for?
Disinfectant (effective against E.coli and S. Aureus)
61
Benzalkonium chloride uses (3)
- Antimicrobial preservative in pharmaceutical formulations - Environmental disinfectant of hard, non-porous surfaces - Antiseptic hand rubs and personal care products
62
Benzalkonium chloride strength (3)
- Non irritating - Non sensitising - Well tolerated in dilutions normally employed on skin and mucous membranes
63
Plant based disinfectants strength (2)
- Nice smell - Effective against E coli, S aureus
64
Why are spores resistant to many disinfectants?
spore coat and cortex act as a barrier
65
What is/are the mechanism(s) of resistance of mycobacteria against disinfectants
1) Waxy cell wall which prevent disinfectant entry 2) Possesses certain compounds that are non-targetable by certain disinfectant
66
What is the mechanism of resistance of gram negative bacteria against disinfectants?
outer membrane that acts as a barrier
67
State and explain at least 2 physical and chemical factors that affect disinfectant efficacy
1) Temperature - In general disinfectant activity increases with increased temperature but if temperature is too high, it may also affect thermal stability of disinfectant leading to decreased [disinfectant] at site of action 2) pH - Activity of certain disinfectants increase with higher pH while others decrease with higher pH. - Low pH influences the antimicrobial activity by altering the disinfectant molecule or the cell surface. 3) Water hardness - Water hardness refer to presence of divalent/multivalent cations in the water. These ions may interact with the disinfectant and form insoluble precipitates leading to decrease in disinfectant activity 4) Excipients used in formulation - Excipients used in the disinfectant formulation must be compatible with the disinfectant to prevent decrease of disinfectant activity 5) Relative humidity - Single most important factor affecting gaseous disinfectant e.g ethanol, chlorine dioxide and formaldehyde
68
Efficacy of which disinfectants increase with increased pH?
Glutaraldehyde, QAC
69
Efficacy of which disinfectant decrease with increased pH?
phenols, hypochlorites, and iodine
70
Explain how organic matter affect disinfectant efficacy
1) Chemical reaction between the germicide --> reduction in potency or full chemical inactivation 2) Protection by occlusion in salt crystals --> complexation leading to precipitation or formation of inclusion complexes that shield the disinfectant and preventing direct contact with the microorganism
71
Which disinfectants are sporicidal?
Aldehydes, Hydrogen peroxide, paracetic acid, Chlorine compounds (e.g sodium hypochlorite)
72
Which low-medium level disinfectant(s) are sporicidal?
Sodium hypochlorite
73
Compare and contrast efficacy of ethanol and propanol as disinfectants
Both are broad spectrum. Propanol slightly more useful in killing bacteria and enveloped viruses (CB say non-enveloped but I disagree because viral envelop is made out of lipids so propanol should be more lipophilic and hence more effective). It is also harder to wash off compared to ethanol because it is more lipophilic Ethanol more useful in killing non-enveloped virus (CB say enveloped)
74
What chemicals present in bacteria may inactivate hydrogen peroxide?
Catalase or other peroxidases
75
Which classes of disinfectants have use as preservatives?
Alcohol QAC Aldehydes Phenols (not as common)

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