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PR3151 CA2: Disinfection & Sterilization (NUS Pharmacy) > IC6 Types of Disinfectants > Flashcards

IC6 Types of Disinfectants Flashcards

1
Q

Sterilization vs Disinfection vs Antisepsis

A

Eliminate all microbial life (Sporicidal)

Eliminate most life (Non-sporicidal) on inanimate surfaces

Eliminate most life (Non-sporicidal) on living tissue

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2
Q

What factors affect the efficacy of disinfection and sterilization?

A

Preconditions
1. Prior Cleaning
2. Organic and inorganic load
3. Microbial contamination level & type

Intrinsic conditions
1. Concentration and exposure time of germicide
2. Number of microbes and innate resistance

Extrinsic conditions
1. Biofilms
2. Physical and chemical environment

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3
Q

Why is cleaning using water with detergent or enzymatic products an important factor affecting disinfection and sterilization?

A

Inorganic and organic materials that remain on the surfaces of instruments interfere with the effectiveness

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4
Q

Why must the location of microorganisms be considered when factors affecting the efficacy of germicides are assessed?

A

Direct contact of disinfectant and microbe

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5
Q

Why is preliminary cleaning important?

A

It increases the margin of safety

It shortens the exposure time required to kill the entire microbial load.

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6
Q

Why is preliminary cleaning important?

A

It increases the margin of safety

It shortens the exposure time required to kill the entire microbial load.

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7
Q

Why is preliminary cleaning important?

A

It increases the margin of safety

It shortens the exposure time required to kill the entire microbial load.

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8
Q

Which 3 microbes generally have greater innate resistance to chemical germicides? What is the mechanism of resistance?

A
  1. Spores - Spore coat and cortex barrier
  2. Mycobacteria - Waxy cell wall
  3. Gram negatives - Outer membrane barrier to disinfectant uptake
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9
Q

What is the relation between concentration and efficacy?

A

Non-linear positive correlation - More concentrated and potent, more efficacious, shorter exposure time

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10
Q

4 physicochemical factors affecting disinfectant efficacy

A
  1. Temperature - Increase activity but can cause degradation
  2. pH - Increase in glutaraldehyde, QAC but decrease in phenols, hypochlorites, iodine
  3. Relative humidity for gaseous disinfectants (Ethanol, formaldehyde)
  4. Water hardness - Divalent cations cause insoluble precipitates
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11
Q

2 ways that organic matter (serum, blood, pus) interfere with antimicrobial activity of disinfectants

A
  1. Chemical reaction with germicides - Form complexes that reduce activity
  2. Physical barrier - Protection by occlusion in salt crystals
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12
Q

What mechanisms of resistance can microbes that are within biofilms have?

A
  1. Older layers of biofilms (Physical)
  2. Genotypic variation
  3. Neutralizing enzyme production
  4. Physiologic gradients within biofilm
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13
Q

What are biofilms?

A

Thick masses of cells and extracellular materials tightly attached to surfaces, difficult to remove

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14
Q

Biofilms are treated with ______________

A

Chlorine compounds and ozone

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15
Q

List of Chemical Disinfectants
(2ABCDE PIP 2 Metal QAC)

A
  1. Alcohols (Ethanol, isopropanol)
  2. Aldehydes (Formaldehyde, Glutaraldehyde, Ortho Phthalaldehyde)
  3. Biguanides (Chlorhexidine, Alexidine)
  4. Chlorine compounds (Hypochlorite, Chloramine, Sodium dichloroisocyanurate)
  5. Diamines
  6. Eucalyptus
  7. Phenols (Chloroxylenol)
  8. Iodine & Iodophors (Povidone-iodine)
  9. Peroxygens (H2O2) & Peracetic acid
  10. Silver Sulfadiazine
  11. Mercuric Chloride
  12. Quaternary Ammonium Compounds (Benzalkonium chloride)
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16
Q

Alcohol uses and in what instance not recommended and why?

A
  1. Disinfection (Hard surface)
  2. Antisepsis (Skin)
  3. Not recommended for surgical material (Non-sporicidal)
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17
Q

What is alcohol’s MOA and what increases its MOA?

A
  1. Bactericidal - Denaturation of proteins
  2. Require water
  3. Bacteriostatic - Inhibition of metabolite production
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18
Q

What are the limitations of ammonia? What can be done to overcome?

A
  1. Eye and GI irritation
  2. Toxic when mixed with bleach
  3. Corrosive => Wear PPE
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19
Q

Ammonia is used for ______

A

Cleaning many surfaces (Glass, Stainless steel)

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20
Q

Which alcohol kills bacteria and non-enveloped viruses and which kills enveloped viruses

A

Isopropanol kills bacteria and non-enveloped viruses (More viscous)

Ethanol kills enveloped viruses

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21
Q

Ammonia MOA?

A

Saponify lipids within enveloped microbes forming precipitation of salt complexes

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22
Q

What are some limitations of aldehydes?

A

Toxicity issues, odour and carcinogen potential

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23
Q

Aldehyde MOA?

A

The biocidal activity of aldehydes results from alkylation of sulfhydryl, hydroxyl, carboxyl and amino groups of microorganisms, which alters RNA, DNA and protein synthesis.

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24
Q

Spectrum activity of aldehydes?

A

Bacterial spores
- Low concentrations inhibit germination; high concentrations are sporicidal because of strong interaction with outer cell layers

Mycobacteria
- Interaction with mycobacterial cell wall

Other non-sporulating bacteria
- Strong association with outer layers of gram-positive and gram-negative bacteria; cross-linking of amino groups in protein; inhibition of transport processes into cell

Fungi
- Fungal cell wall with possible interaction with chitin

Viruses
- Protein DNA cross-links and capsid changes

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25
Q

Uses of different aldehydes

A

Sterilant (Formaldehyde - Sporicidal)

High-level Disinfectant (Both Formaldehyde and Glutaraldehyde)

Formaldehyde - Viral vaccines prep

Glutaraldehyde - Medical equipment

Paraformaldehyde - Laminar flowhood

26
Q

OPA uptake, MOA, Spectrum activity

A

Uptake through outer layer due to lipophilic aromatic nature

Cross-linking agent to amino acids, protein, DNA

Sporicidal, Mycobacteria, Gram negatives

27
Q

OPA - What type of disinfectant, advantage and disadvantage?

A

High-level disinfectant

Advantage - pH stable; less eye and nose irritation, and odour, only need 5 min contact time

Disadvantage - Gray staining on skin

28
Q

Biguanide spectrum activity? Bacteria? Viruses? Spores?

A

Broadspectrum bactericidal

Limited against viruses

Non-sporicidal

29
Q

Biguanides MOA? (Chlorhexidine and Alexidine)

A

React with negatively charged groups on cell membrane, altering the permeability

Chlorhexidine - Damage membrane, cross by passive diffusion (pH dependent)

Alexidine - Lipid phase separation destroying the membrane

30
Q

What factors affect biguanide disinfectant efficacy?

A

Organic matter and cleaning soap reduce efficacy

31
Q

Chlorine compounds MOA?

A
  1. Oxidation of Sulfhydryl enzymes & AA
  2. Ring chlorination of AA
  3. Protein synthesis inhibition
  4. DNA disruption
  5. Intracellular content loss
32
Q

Advantage of using chlorine compounds? (Spectrum? Toxicity? Physical factors & efficacy? Cost?)

A

Broad spectrum, non-toxic, not affected by water hardness, useful against biofilms, cheap

33
Q

Disadvantage of chlorine compounds? (For users? Factors affecting efficacy?)

A
  1. Eye and GI irritation
  2. Metal corrosiveness
  3. Organic matter inactivation
  4. Toxic gas is released
34
Q

What factor increases hypochlorite activity?

A

pH increase allows less conversion of HOCl to OCl

35
Q

Which chloride compound retains chlorine longer to exert longer effects?

A

Chloramine

36
Q

Which chlorine compound is in tablet form and why?

A

Sodium dichloroisocyanurate

When free chlorine is used up, equilibrium can be restored since only 50% of total chlorine is free

37
Q

Iodine and Iodophor MOA?

A

Penetrate cell wall quickly and disrupt protein & nucleic acid structure & synthesis

38
Q

Iodine and Iodophors are used as _____

A

Antiseptic for Skin and Tissue (Iodine)

Antiseptic and disinfectant for medical equipment (Iodophors)

39
Q

What are iodophors made up of and their purpose?

A

Solubilizing agent with iodine to provide a sustained release reservoir for free iodine

40
Q

How does dilution affect Iodophors?

A

The linkage between iodine and solubilizing agent

41
Q

Peroxygen (H2O2) MOA?

A

Oxidant producing free radicals attack membrane lipids and DNA

42
Q

H2O2 is used for _____ and spectrum activity covers _______

A

Disinfection, Sterilization, Antisepsis

Bactericidal, Sporicidal (At high conc)

43
Q

How do surfactants, chelating agents and emulsifiers accelerate H2O2 activity?

A

Surfactant - Alkali metal & ammonium salt disrupt bacterial cell membrane

Chelating agent - Phosphoric acid forms stable complex

Emulsifier - Alkylated diphenyl oxide forms micelles containing equal dispersions of the product

44
Q

Peracetic acid MOA

A

Denature proteins and enzymes and increases cell wall permeability by disrupting sulfhydryl (-SH) and sulfur (S-S) bonds.

45
Q

Advantage of peracetic acid

A

It also decomposes to safe by-products (acetic acid and oxygen) but has the added advantages of being free from decomposition by peroxidases, unlike H2O2, and remaining active in the presence of organic loads.

46
Q

Main application of peracetic acid

A

Low temperature liquid sterilant for medical devices and environmental surface sterilant.

47
Q

Phenol MOA?

A

Phenol induces progressive leakage of intracellular constituents, including the
release of K+, which it usually is the first index of membrane damage.

48
Q

Phenol spectrum activity?

A

Antifungal (damage to the plasma membrane) and antiviral properties.

49
Q

Chloroxylenol MOA?

A

Disruption of microbial cell walls and inactivation of cellular enzymes.

50
Q

Chloroxylenol - How toxic?

A

Relatively nontoxic and nonirritant material when used as an excipient in topical products, but it is toxic upon oral consumption or eye contact.

51
Q

Diamidine MOA?

A

Inhibition of oxygen uptake and leakage of amino acids.

52
Q

Example of diamidine and uses

A

Propamidine

Bacteriostatic agents for the topical treatment of wound.

53
Q

Silver sulfadiazine Spectrum activity

A

Antibacterial agent combination

54
Q

Mercuric chloride MOA?

A

Broad range disinfectant, which affect microbial peptide synthesis.

55
Q

Mercuric chloride cautions?

A

Highly toxic compound, both acutely and as a cumulative poison. It is toxic and corrosive.

Tends to accumulate in the kidneys, causing severe corrosive damage which can lead to acute kidney failure.

56
Q

QAC MOA?

A

(i) Adsorption and penetration of cell wall
(ii) Reaction with the cytoplasmic membrane (lipid or protein) followed by membrane disorganization;
(iii) Leakage of intracellular low-molecular-weight material;
(iv) Degradation of proteins and nucleic acids;
(v) Wall lysis caused by autolytic enzymes.

57
Q

Why are QAC sometimes called cationic detergents?

A

They have been used for a variety of clinical purposes (e.g., preoperative disinfection of unbroken skin, application to mucous membranes, and disinfection of noncritical surfaces).

58
Q

Are QAC sporicidal?

A

No

59
Q

When do we use vapor phase sterilants? Other than vapor phase sterilants, what else can be used?

A

Heat-sensitive medical devices and surgical supplies

Liquid sterilants (Glutaraldehyde, peracetic acid, H2O2)

60
Q

Vapor sterilants include

A

Ethylene oxide and formaldehyde

61
Q

Safety differences for the vapor sterilants

A

Ethylene oxide is safer for humans but more dangerous to use (explosive)

Formaldehyde is safer for close environment (machine insulators where humans cannot go in)

62
Q

What is infectious dose?

A

Minimum amount to cause infection

PR3151 CA2: Disinfection & Sterilization (NUS Pharmacy) (5 decks)

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