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PR3151 Disinfectants and Sterilization > IC6 Chemical disinfectants 1 > Flashcards

IC6 Chemical disinfectants 1 Flashcards

1
Q

How do emollients and surfactants enhance activity of disinfectants?

A

Emollients: make skin softer, allow penetration through first layer of skin

Surfactant: disrupt outer layer of viruses and bacteria, make them more sensitive to disinfectant

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2
Q

What is the mechanism of action of alcohols? *alcohols can be used as disinfectant and antiseptic

A

Alcohols lead to denaturation of proteins, this mechanism is increased by water => faster denaturation

Alcohol also bacteriostatic by inhibition of the production of metabolites essential for rapid cell division

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3
Q

Describe the spectrum of activity of alcohols? *alcohols can be used as disinfectant and antiseptic

A

Broad-spectrum of activity, against vegetative bacteria (including mycobacteria, tuberculocidal), virus, fungi

NOT sporicidal

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4
Q

Isopropyl alcohol and ethanol have optimal antimicrobial activity in the 60-90% range. Compare the efficacy of the two in terms of spectrum + time required

A

SPECTRUM:
Isopropyl alcohol: more lipophilic, more efficacious against bacteria + non-enveloped virus
Ethanol: more potent against enveloped virus

TIME REQUIRED:
Isopropyl: has thick consistency, can stay on surface for longer time => shorter time to achieve same effect
Ethanol: vaporizes easily due to low BP, => need longer time to achieve same effect

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5
Q

Alcohol advantages and disadvantages

A

Advantages
- no toxic residue
- noncorrosive
- nonstaining

Disadvantages
- affected by organic matter
- slow acting on nonenveloped viruses
- no detergent or cleaning properties
- flammable
- evaporates rapidly, making contact time compliance difficult
- can cause damage to rubber and plastic

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6
Q

What is the mechanism of action of Ammonia (used as disinfectant)?

A

Saponify lipids within the envelopes of microorganisms
*aq ammonium salt complex with lipid layer of microorganism, precipitate

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7
Q

Describe the irritant properties of ammonia?

A

Irritant for eyes and gastric system

If mixed with bleach, it may release chloramine which is toxic
*Chloramine itself is a disinfectant used to treat drinking water, but it should not be ingested

Pungent gas

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8
Q

What is Aldehyde (disinfectant) mechanism of action?

*Can also be used as preservative in low conc. in vaccines (preserve and inactivate virus)

A

Alkylation (cross linking) of sulfhydryl, hydroxyl, carboxyl, and amino groups of microorganisms => alters RNA, DNA, and protein synthesis
*Cross links proteins, RNA, DNA => denature proteins, disrupt nucleic acid, disrupt synthesis

Also interacts with cell wall/outer layers of mycobacteria, fungi, spores, gram-negative bacteria

**Glutaraldehyde: only cross links proteins
**Otho-phthalaldehyde: irreversibly cross links DNA

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9
Q

What is Aldehyde (disinfectant) spectrum of activity?

A

Broad spectrum of activity

Bacterial spores: low conc. inhibit germination, high conc. sporicidal due to strong interaction w spore coat (outer cell layer)

Mycobacteria: interact with waxy cell wall

Vegetative bacteria: strong association with outer layer of gram negative; cross linking of amino groups in protein; inhibition of transport processes into cell

Fungi: interaction with chitin in fungal cell wall

Virus: protein/DNA cross links and capsid changes

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10
Q

Aldehydes cant be used as antiseptic due to its toxicity. What are the toxicites?

A

Reactive species, highly irritating and toxic with contact or inhalation (respiratory irritation), possibly carcinogenic

Strong (pungent and irritating) odors

*Excellent material compatibility

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11
Q

Efficacy of formaldehyde is dependent on ____

A

Relative humidity, close to 70%

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12
Q

What is paraformaldehyde?

A

solid polymer of formaldehyde, can be vaporized by heat for the gaseous decontamination of laminar flow biologic safety cabinets

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13
Q

Glutaraldehyde properties

A

Highly dependent on pH (>7)
More efficacious in the presence of organic matter, soaps, and hard water than formaldehyde

2% is used for high level disinfection

Pungent and irritating odor

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14
Q

What is the advantage of ortho-phthalaldehyde (OPA) over aldehyde?

A

Otho-phthalaldehyde (OPA) is a cross-linking (alkylating) agent, irreversibly cross links DNA of bacteria, also blocks spore germination

It interacts with amino acids, protein, and microorganisms, but its LIPOPHILIICITY can assist uptake through OUTER LAYERS of mycobacteria and gram-negative bacteria

Thus, can penetrate cell faster (useful if theres time constraint)

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15
Q

What are the properties of Ortho-phthalaldehyde (OPA)?

A

Clear, pale blue solution, pH 7.5
Excellent stability over wide range of pH 3-9
Excellent material compatibility

Not an irritant to eyes and nasal passage (while other aldehydes are)
No odor (while other aldehydes have strong pungent odors)

HOWEVER, it stains proteins gray (can stain skin, mucous membrane, clothing, surfaces)
Can cause eye irritant with contact

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16
Q

What are two Biguanides (antiseptic, disinfectant)?

A

Chlorhexidine
Alexidine

17
Q

What is Biguanide mechanism of action?

A

Damage membrane + cytoplasm by:

  1. Damage cell membrane by reacting with the negatively charged groups on cell membrane, alter its permeability (FYI details)
  2. Crosses the cell outer membrane by passive diffusion
  3. Attack bacterial cytoplasmic or inner membrane OR the yeast plasma membrane
    *cause coagulation or gelling of the cytoplasm
18
Q

What is Biguanide (disinfectant, antiseptic) spectrum of activity?

A

Biguanides have broad spectrum of activity.
Limited effectiveness against virus
Not sporicidal, mycobactericidal, or fungicidal

19
Q

What factors may affect Chlorhexidine activity?

A
  1. pH
    pH dependent, only function in limited range of pH 5-7
  2. Easily inactivated by organic matter
    Activity greatly reduced in presence of organic matter (either due to complexation or reduced amount of agent at site)
  3. Easily inactivated by soups and detergents:
    - Incompatible with soaps, detergents and other anionic materials as Chlorhexidine salts are cationic in solution
  4. Surfactants:
    - Compatible with cationic and nonionic surfactants
    - In high conc. of surfactants, micellar binding may reduce Chlorhexidine activity
20
Q

How does Alexidine differ from Chlorhexidine in terms of chemical structure?
What does this confer?

A

Alexidine possess ethylhexyl end groups

  1. This confers faster onset of bactericidal activity, produces faster alteration in bactericidal permeability
  2. Alexidine produces lipid phase separation which causes apoptosis via destruction of bacterial membrane
21
Q

What are the 3 disinfectants that release chlorine?

A
  1. Hypochlorites
  2. Chloramine
  3. Sodium dichloroisocyanurate (tablets)
22
Q

What is hypochlorite MOA?

A

Oxidation of sulfhydryl enzymes and amino acids

Ring chlorination of amino acids

Inhibition of protein synthesis

DNA disruption

Loss of intracellular contents

23
Q

What is hypochlorite spectrum of activity?

A

Broad spectrum
- Vegetative bacteria
- Enveloped and non-enveloped virus (HIV, HBV, lipovirus, non-lipid virus)
- Mycobacteria (Tb)
- Fungi
- Can be sporicidal at elevated conc.

*Useful against biofilms as well

24
Q

What factors affect Hypochlorite activity?

A
  1. Activity is pH dependent
    HOCl (hypochlorous acid) dissociates to OCl- ion at high pH, OCl- has less microbicidal activity
    => Efficacy dcr with incr in pH (more effective at acidic pH where it exist as HOCl)
  2. Activity is greatly reduced by presence of organic matter
    Chemical inactivation by organic matter
25
Q

What formulations do Hypochlorite come in?

A

Liquid - sodium hypochlorite solution
Solid - calcium hypochlorite

26
Q

What are the advantages of hypochlorite?

A
  1. low toxicity, do not leave toxic residues
  2. unaffected by water hardness
  3. inexpensive
  4. fast acting
  5. able to remove dried or fixed organisms and biofilms from surfaces
  6. not flammable
  7. used as disinfectant in water
27
Q

What are the disadvantages of hypochlorite?

A
  1. ocular irritation + skin irritation => use PPE
  2. burns (mouth, throat, stomach) => dont ingest
  3. corrosive to metals at high conc. => think about material compatibility
  4. chemically inactivated by organic matter
  5. release of toxic chlorine gas
  6. leaves salt residue
  7. reaction hazard with acids and ammonia => chloramine gas
  8. discolors/stains fabric
  9. odor
28
Q

Chloramine and sodium dichloroisocyanurate exert more prolonged bactericidal effect than hypochlorite because _____

A

They retain chlorine longer

Sodium dichloroisocyanurate tablets are stable and long release

29
Q

Sodium dichloroisocyanurate tablets (used for disinfection, cleaning, antiseptic) are more stable and have longer release compared to Sodium hypochlorite solutions

Explain how Sodium dichloroisocyanurate tablets work

A

With solution prepared from Sodium dichloroisocyanurate tablets, only 50% of the total available chlorine is free (HOCl and OCl-), whereas the remainder is combined (monochloroisocyanurate or dichloroisocyanurate)

As free chlorine is used up, more chlorine is released from the remainder to restore equilibrium. This ensures that chlorine conc. in liquid component can stay stable for a long time.

This is in contrast to Sodium hypochlorite solutions whereby 100% of solution exist as free HOCl and OCl- => chlorine evaporates quickly, hard to store

30
Q

What is the mechanism of action of iodine (antiseptic, disinfectant)?

A

Penetrate the cell wall of microorganisms quickly, leading to disruption of protein and nucleic acid structure and synthesis

*lose potency at pH >9 (lower pH better)

31
Q

What is iodine (antiseptic, disinfectant) spectrum of activity?

A

Broad spectrum
- Bacteria
- Mycobacteria (Tb)
- Fungi (prolong contact)
- Virus (lipovirus, non-lipid virus, HIV)

No activity against spores

32
Q

What is iodophor?

A

Combination of iodine and a solubilizing agent or carrier

e.g., povidone-iodine, a compound of polyvinylpyrrolidone with iodine

33
Q

What is the benefit of iodophor (iodine + solubilizing agent)?

A
  • sustained-release reservoir of iodine
  • increased solubility
  • less readily inactivated by organic matter compared to iodine compound (iodine compound is inactivated and organic debris and QAC)
  • less irritating than iodine
34
Q

Explain how iodophor achieves sustained-release?

How might we incr the release of free iodine?

A

Sustained release: Free iodine, which contributes to the bactericidal activity of iodophor, is released in small amounts, allowing concentration to be above minimum effective concentration for a longer period of time.

Dilutions of iodophor have more rapid bactericidal activity because dilution can weaken the iodine linkage to the carrier polymer, allowing increase in release of free iodine in the solution.

35
Q

Properties of iodine

A

-ve:
concentrated iodine can be irritating to skin
can stain clothes
damage rubber and some metals
inactivated by QACs and organic debris

36
Q

Properties of iodophor

A

Not flammable
Less inactivated by organic matter compared to iodine

-ve:
Not sporicidal
Require prolonged contact to kill fungi
Stain surfaces

PR3151 Disinfectants and Sterilization (10 decks)

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