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PR3151 Disinfectants and Sterilization > IC6 Chemical Disinfectants 2 > Flashcards

IC6 Chemical Disinfectants 2 Flashcards

1
Q

Hydrogen peroxide is a peroxygen, used for disinfection, sterilization, and antisepsis. What is hydrogen peroxide MOA?

A

H2O2 acts as an oxidizing agent by producing hydroxyl free radicals

Radicals induce oxidation of the compound in the outer layer of microorganisms and attack essential cell components including lipids, proteins, and DNA

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2
Q

Hydrogen peroxide is a peroxygen, used for disinfection, sterilization, and antisepsis.
What is its spectrum of activity?

A

Broad spectrum of activity,
Virus (non-enveloped virus may be resistant)
Bacteria (greater activity against gram-positive than gram-negative)
Yeast
Bacterial spores (higher conc. + longer contact time for sporicidal activity)

Limited activity against mycobacteria

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3
Q

How might resistance towards hydrogen peroxide arise?

A

Microorganisms (esp biofilms) may produce enzymes:

  • Catalase, Peroxidase can decompose/cleave peroxide and incr tolerance of organisms in low H2O2 concentrations
  • Specific enzymes that inactivate radicals
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4
Q

What are the properties of Hydrogen Peroxide?

A
  • Clear, colorless liquid, conc. can range from 3-90%
  • Most contain stabilizers (e.g., sodium citrate or malonate) to prevent decomposition during storage [*sodium citrate - adjust pH, sequestering agent, blood coagulant]
  • No odor or irritation issues
  • High concentration can be irritant
  • Eye irritant

*Affected/inactivated by organic load (due to peroxidases)
*Incompatible with metal (brass, zinc, copper, nickel/silver)

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5
Q

Accelerated hydrogen peroxide
- stabilized H2O2 so that it can be used for extended periods of time
- has enhanced antibacterial efficacy due to addition of:

A
  1. Surfactant
    - Disrupt cell outer layer, allow easier/faster entry of H2O2 into cell
    - E.g., alkali metal and ammonium salts, alkyl sulphate
  2. Organic acid (chelating agent)
    - Chelate/form complex with salts/ions present that may decrease activity or inactivate the radical
    - e.g., phosphonic acid, phosphonate
  3. Emulsifier
    - disperse product in micelles to keep it stable
    - e.g., alkylated diphenyl oxide
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6
Q

Accelerated H2O2 is usually used on ____

A

Medical or veterinary devices

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7
Q

What are some advantages and disadvantages of accelerated H2O2?

A

Advantages:
- safe for workers and environment
- nonstaining
- not flammable

Disadvantages
- Short shelf life due to decomposition of H2O2, oxygen can vaporize easily
- Irritant for the eyes (but safer than chlorine)
- not sporicidal at low conc.
- some material incompatibility

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8
Q

What is Peracetic acid MOA?

A

Peracetic acid is a strong oxidizing agent.

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

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9
Q

Peracetic acid is more potent than H2O2. What is its spectrum of activity?

A

Broad spectrum of activity,
Sporicidal
Bactericidal
Virucidal (not so much)
Fungicidal

all at low conc. 0.3%

also effective against mycobacteria and algae

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10
Q

What are the advantages of Peracetic acid?

A
  1. Decompose to safe and enrivonmentally friendly by products: acetic acid + oxygen + water
  2. Free from decomposition by peroxidases (unlike H2O2)
  3. Retain some activity in the presence of organic loads (but still affected by organic residue)
  4. It can be used as a low temperature liquid sterilant => effective at low conc + low temp
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11
Q

Describe the MOA of vinegar (acetic acid)

A

Protein precipitation, destroy nucleic acids bond

*often used together with salt

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12
Q

What is the role of salt?

A

able to induce death by osmosis (draw water out of microorganism cell)

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13
Q

What is the MOA of phenols? *phenols used as antiseptic, disinfectant, preservative

A

Induce progressive leakage of intracellular constituents, including the release of K+, which is the first index of membrane damage

*work better at lower pH

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14
Q

What is the spectrum of activity of phenols?

A

Bactericidal
Tuberculocidal
Fungicidal
Some antiviral properties (NOT effective against non-enveloped viruses)

NOT effective against spores

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15
Q

What are the advantages and disadvantages of phenol?

A

Advantages:
Maintain activity in hard water
Maintain activity in presence of organic matter
Some residual activity after drying
Nonstaining
Not flammable
Can be formulated with soaps to increase penetration

Disadvantages:
Depigmentation of skin
Hyperbilirubinemia in infants
Not compatible with nonionic detergents

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16
Q

What is the MOA of Chloroxylenol? *antiseptic, disinfectant, injectable or ophthalmic antimicrobial
What is its spectrum of activity?

A

Disrupt microbial cell wall, inactivate cellular enzymes

Bactericidal

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17
Q

Chloroxylenol is realtively nontoxic and nonirritant as an excipient in topical products, however, it is toxic upon ______ or _______

A

Toxic upon oral consumption or eye contact

18
Q

Chloroxylenol is often used in combination with edetic acid. Explain the role of edetic acid.

A

Edetic acid is a chelating agent and sequestering agent. It can form stable complex with trace amount of metal ions that may inactivate the main disinfectant.

19
Q

What is the MOA of diamidines? *antiseptic, disinfectant

A

inhibit oxygen uptake, cause leakage of amino acids

20
Q

What can diamidines be used for?

A

Bacteriostatic agent for the treatment of wound
*antiseptic

21
Q

Silver (Ag+) compounds can include silver nitrate and silver sulfadiazine.

Explain the MOA and spectrum of activity of silver ions? *

A

Silver ions can interact with thiol (sulfhydryl, -SH) groups in enzymes and proteins**, affect microbial plasma, cytoplasmic membrane, DNA and nucleic acids

Antimicrobial, antifungal

22
Q

SIlver sulfadiazine is used in ____

A

treatment of burn

23
Q

Why is the advantage of silver sulfadiazine over silver nitrate?

A

It is the combi of silver + antibiotic sulfadiazine
Hence it has broader spectrum
It can induce membrane blebs in susceptible bacteria

(Blebs: blister like protrusion filled with serous fluid)

24
Q

What is mercuric chloride mechanism of action? *disinfectant

A

Affect microbial peptide synthesis

25
Q

Why is mercuric chloride no longer used?

A

Highly toxic and corrosive, both acutely and as a cumulative poison (cannot be expelled from the body as it diffuses to fat tissues and stays there)

Tends to accumulate in the kidneys => severe corrosive damage => acute kidney failure

26
Q

What are QACs mechanism of action?

A

QAC is a cationic detergent (attracted to -ve charge in phospholipid of cell membrane)

Its mechanisms are:
1. Adsorption and penetration into cell wall
2. Reaction with cytoplasmic membrane (lipid or protein) followed by membrane disorganization
3. Leakage of intracellular low-molecular weight material
4. Degradation of proteins and nucleic acids
5. Wall lysis caused by autolytic enzymes

Work better at neutral-alkaline pH, lost activity at pH <3.5

27
Q

What is the spectrum of activity of QACs?

A

Fungicidal
Bacterical
Virucidal against lipophilic enveloped viruses

NOT sporicidal but may be sporistatic
NOT effective against non-enveloped viruses or mycobacteria
NOT tuberculocidal

Some residual bacteriostatic effect

28
Q

What are the uses of QAC as antiseptic and disinfectant.

A

Antiseptic: preoperative disinfection of unbroken/intact skin

Disinfectant: noncritical surfaces - floor, furniture, walls

29
Q

Why is QAC not used on broken skin?

A
  1. Painful
  2. Can cause cell lysis of own cell (through its MOA)
30
Q

QACs are easily inactivated by __________________________

A

organic matter, detergents, soaps, hard water

31
Q

Benzalkonium chloride is a QAC used as antimicrobial preservative
Why is its spectrum of activity? What is its activity dependent on?

A

Bacteria, yeast, fungi
- more activity against gram positive than negative

Minimal activity against bacterial endospores and mycobacteria

Activity is dependent on the alkyl composition of the homolog mixture

32
Q

What are the properties of benzalkonium chloride?

A

Non-irritating, non-sensitizing, well tolerated in dilutions normally employed on skin and mucous membrane

Therefore can be used as preservative e.g., in eyedrops

However, potential environmental impact - disruption of wastewater treatment, proliferation of antibiotic resistance, nitrosamine byproducts
- *QAC and Biguanides toxic to fish, do not discard in water sources

33
Q

Benzalkonium can be used with cetrimide (surfactant). How does cetrimide enhance effect of benzalkonium chloride?

*Cetrimide itself is also a QAC, used as antiseptic

A

Cetrimide surfactant disrupt outer layer, allow benzalkonium to penetrate more quickly to exert its action intracellularly

34
Q

What are some other methods for disinfection? How do they work?

A
  1. Plant based disinfection - eucalyptus, more bearable smell than ammonia or alcohol
  2. UV lamp disinfection - short wavelength UV light to kill or inactive microorganism by destroying nucleic acids and disrupting DNA
35
Q

What influences the effectiveness of UV light disinfection?

A
  1. exposure time
  2. intensity and wavelength of UV radiation
  3. presence of interfering particles
  4. microorganism innate UV resistance
  5. line of sight exposure of microorganism to UV light, therefore repeated cycle can be used to ensure proper disinfection
36
Q

Which disinfectants have activity against spores?

A

Aldehydes - low conc sporistatic, high conc sporicidal
Chlorine compounds - sporicidal at elevated conc.
Hydrogen Peroxide - high conc. + longer contact time for sporicidal activity
Peracetic acid - sporicidal at low conc.
QAC - sporistatic at best

37
Q

What is the MOA of EDTA?

A

It is a chelating agent and anticoagulation agent

  1. Remove Mg2+ and lipopolysaccharides (LPS) from gram negative
  2. Chelate ions, prevent complexation between ions and disinfectant
38
Q

What is the MOA of acridines?

A

Intercalation of RNA and DNA

*used as a dye

39
Q

Which disinfectants may be used as preservatives (at low doses)?

A

Chlorhexidine
Aldehyde
Phenol
Benzalkonium Chloride

40
Q

Why can’t peracetic acid and accelerated hydrogen peroxide be used to disinfect water?

A

Peracetic acid: residue acetic acid need to be eliminated

Accelerated hydrogen peroxide: while hydrogen peroxide break down into H2O and O2 may not be an issue, the surfactant + emollient + chelating agent may need to be removed

PR3151 Disinfectants and Sterilization (10 decks)

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