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PR3151 CA2 > IC6 - Disinfectants > Flashcards

IC6 - Disinfectants Flashcards

1
Q

Sterilisation

A

Process that eliminates ALL forms of microbial life carried out in health-care facilities by physical or chemical methods

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2
Q

Disinfection

A

Process that eliminates MANY or ALL pathogenic microorganisms EXCEPT for bacterial spores, on INANIMATE objects

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3
Q

Factors affecting the efficacy of disinfectants

A
  1. Prior cleaning of object*
  2. Organic and Inorganic load present
  3. Type and level of microbial contamination
  4. Concentration and exposure time to the germicide*
  5. Physical nature of the object (total surface area)
  6. Presence of biofilms*
  7. Temperature and pH of disinfection
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4
Q

Chemical Sterilants

A

Disinfectants that kill spores upon prolonged exposure (3-12 hours)

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5
Q

High-level Disinfectant

A

Kill all microorganisms except bacterial spores with the usual concentration and short exposure time period eg. Aldehydes

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6
Q

Cleaning

A

Removing visible soil

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7
Q

Biocides

A

Broader spectrum of activity than antibiotics and have multiple targets. COmprises of disinfectants and antiseptics

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8
Q

Examples of innate resistance of microorganisms

A
  1. Spores - spore coat and cortex act as barrier
  2. Mycobacteria - waxy cell wall that prevents disinfectant entry
  3. Gram-negative bacteria - outer membrane that acts as a barrier to the uptake of disinfectants
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9
Q

How does temperature affect disinfectant efficacy?

A

Most stable disinfectant increase in efficacy at higher temperatures.
However, some may suffer degradation (eg. ethanol evaporating in hot environment)

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10
Q

How does pH affect disinfectant efficacy?

A

pH can either affect cell or disinfectant. Recommended pH> 4-5

Increase in pH improves antimicrobial activity of some disinfectants (eg. aldehydes and QAC).

However, it may decrease antimicrobial activity (eg. phenols, hypochlorites and iodine).

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11
Q

How does relative humidity affect disinfectant efficacy?

A

Gaseous disinfectants, water added improve antimicrobial activity (eg. ethanol, formaldehyde, CO2)

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12
Q

How does water hardness affect disinfectant efficacy?

A

Decrease kill of some disinfectants because divalent cations in hard water interact with disinfectants to form insoluble precipitates, leading to less disinfectant available at site of action

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13
Q

How does organic/inorganic matter affect disinfectant efficacy?

A
  1. Chemical reaction with disinfectant, reducing potency or inactivating it.
  2. Protection by occlusion in salt crystals via precipitation (less common) or inclusion (more common)
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14
Q

Biofilms

A

Resistant to disinfectants via multiple mechanisms
1. Layers of older biofilms (survive after selection pressure has been applied)
2. Genotype variation* (Environment favors this)
3. Neutralizing enzymes
4. Physiologic conditions

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15
Q

MOA of Alcohols

A

Denatures proteins (activity increases with H20), bacteriostatic by inhibiting production of metabolites essential for rapid cell division

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16
Q

Isopropyl VS Ethanol

A

Isopropyl more lipophilic and viscous, more efficacious against bacteria and non-enveloped viruses, Ethanol more efficacious for enveloped virus

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17
Q

MOA of Ammonia

A

Saponifying lipids (complex lipids into salt) within the envelopes of microorganisms

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18
Q

Ammonia disinfectants

A

Irritant to eyes and gastric system (pH: 11-12)

Eg. mixed with bleach to give toxic chloramine.

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19
Q

MOA of Aldehyde

A

Alkylation of SH, OH, CO, NH2 groups of microorganisms, alters RNA, DNA and protein synthesis.

20
Q

Aldehyde disinfectants

A

High-level disinfectant, large spectrum of activity.
Liquid or Gaseous (more common).
Toxic and much odour, not used for antiseptic.
Eg. Paraformaldehyde, Ortho-phthaldehyde (OPA)

21
Q

Ortho-phthaldehyde (OPA)

A

Action: Cross-linking agent, may block the germination process, and lipophilic to assist uptake through mycobacteria and gram-negative bacteria.

Stable at a wide pH range, less irritant to eyes and nasal passage, odourless

22
Q

Chlorhexidine (Biguanides)

A

Broad spectrum bactericidal agent. pH and organic matter affect activity.

23
Q

MOA of Chlorhexidine (Biguanides)

A
  1. Damage membrane
  2. Cross cell outer membrane by passive diffusion
  3. attacks bacterial cytoplasmic or inner membrane or the yeast plasma membrane
24
Q

Alexidine VS Chlorhexidine (Biguanides)

A

Alexidine faster onset of bactericidal activity, faster alteration in bactericidal permeability, produce lipid phase separation to destroy bacterial membrane.

25
Q

MOA of Chlorine and Chlorine compounds

A
  1. Oxidation of SH enzymes and AA
  2. Ring chlorination of AA
  3. Inhibition of protein synthesis
  4. DNA disruption
  5. Loss of intracellular contents
26
Q

Adv of Chlorine and Chlorine Compounds (Hypochlorites)

A
  1. Broad spectrum activity
  2. No toxic residues
  3. Unaffected by water hardness
  4. Used against biofilm
  5. Cheap
27
Q

Disadv of Chlorine and Chlorine Compounds (Hypochlorites)

A
  1. Occular Irritation
  2. Burns (mouth, throat, stomach)
  3. Corrosiveness to metals in high concentrations
  4. Inactivated by organic matter
  5. Release if toxic chlorine gas
  6. Decreased efficacy when increase in pH (dissociation of more active HOCl-)
28
Q

Alternative Chlorine Compounds

A

Chloramine, Sodium dichloroisocyanurate (solid tablets) - keep concentrations high for longer time, prolonged bactericidal effect

29
Q

MOA of Iodine and Iodophors

A

penetrate cell wall quickly and disrupt protein and nucleic acid structure and synthesis

30
Q

Iodophor

A

Combination of iodine and solubilizing agent, the complex provides a sustained-release reservoir of iodine and releases a small amount of free iodine. EG. polyvinylpyrrolidone with iodine. Dilution of povidone-iodine weakens iodine linkage to carrier, more free iodine, better activity

31
Q

Adv of Iodine and Iodophors

A

Can be used as antiseptic and disinfectant

32
Q

MOA of Peroxygens (H2O2)

A

H2O2 acts as an oxidant by producing OH free radicals that attack essential cell components (lipids, proteins and DNA), destroying membrane.

33
Q

Adv of Peroxygens

A
  1. Stable liquid *may contain stabilisers to prevent decomposition)
  2. (High-level disinfectant) broad-spectrum efficacy against all viruses, bacteria, yeasts, and bacterial spores
34
Q

Disadv of Peroxygens

A
  1. More gram-pos cover, less-gram neg cover
  2. Catalase and peroxidase in microorganisms decrease activity of peroxygens
35
Q

Accelerated hydrogen peroxide

A

More efficacious than H2O2
1. has surfactant to disrupt bacterial cell outer layer
2. has chelating agent to reduce water hardness and metal content
3. has emulsifier to improve stability and prolong activity

36
Q

Peracetic acid

A

More potent than H2O2 (Sterilant)

MOA: denatures proteins and enzymes and increase cell wall permeability by disrupting SH and S-S bonds

Safer and not subject to decomposition

Low temperature liqid sterilant

37
Q

MOA of Phenols

A

Induces progressive leakage of intracellular constituents, release of K+, causing membrane damage.

38
Q

Uses of Phenols

A

Antifungal and Antiviral properties
Antiseptic, disinfectant and preservative

39
Q

Chloroxylenol

A

MOA: disrupt microbial cell walls, inactivate cellular enzymes

Nontoxic and nonirritant but not to be consumed or used in eye contact.

Used with chelating agent to reduce activation by calcium ions

40
Q

Diamidines

A

Bacteriostatic agents used in wound treatment

MOA: Inhibits oxygen uptake and leakage of AA, killing microorganism

41
Q

Silver compounds

A

Antifungal properties
Silver ions interact with thiol (SH) groups in enzymes and proteins, plasma, cytoplasmic membrane and nucleic acids

Silver sulfadiazine: broader spectrum inducing membrane blebs in susceptible bacteria

42
Q

MOA of QAC

A
  1. adsorption and penetrate cell wall
  2. React with cytoplasmic membrane and cause membrane disorganization
  3. Leakage of intracellular low molecular weight material
  4. Degradation of proteins and nucleic acids
  5. Wall lysis caused by autolytic enzymes
43
Q

Uses of QAC

A

Cationic detergents, broad spectrum.
Bactericidal, fungicidal, virucidal against enveloped viruses.
Disinfection of UNBROKEN skin

44
Q

Benzalkonium Chloride

A

QAC used as preservative

More gram-pos than gram neg coverage.
Minimal activity against bacterial endospores and acid-fast bacteria

Activity dependent on alkyl composition of mixture

45
Q

Vapor Phase Sterilants

A

glutaraldehyde, peracetic acid and H2O2

Ethylene oxide and formaldehyde (broad spectrum alkylating agents), reactive with SH and enzyme-reactive groups

PR3151 CA2 (1 decks)

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