IC6 Chemical disinfectants 1 Flashcards
How do emollients and surfactants enhance activity of disinfectants?
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
What is the mechanism of action of alcohols? *alcohols can be used as disinfectant and antiseptic
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
Describe the spectrum of activity of alcohols? *alcohols can be used as disinfectant and antiseptic
Broad-spectrum of activity, against vegetative bacteria (including mycobacteria, tuberculocidal), virus, fungi
NOT sporicidal
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
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
Alcohol advantages and disadvantages
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
What is the mechanism of action of Ammonia (used as disinfectant)?
Saponify lipids within the envelopes of microorganisms
*aq ammonium salt complex with lipid layer of microorganism, precipitate
Describe the irritant properties of ammonia?
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
What is Aldehyde (disinfectant) mechanism of action?
*Can also be used as preservative in low conc. in vaccines (preserve and inactivate virus)
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
What is Aldehyde (disinfectant) spectrum of activity?
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
Aldehydes cant be used as antiseptic due to its toxicity. What are the toxicites?
Reactive species, highly irritating and toxic with contact or inhalation (respiratory irritation), possibly carcinogenic
Strong (pungent and irritating) odors
*Excellent material compatibility
Efficacy of formaldehyde is dependent on ____
Relative humidity, close to 70%
What is paraformaldehyde?
solid polymer of formaldehyde, can be vaporized by heat for the gaseous decontamination of laminar flow biologic safety cabinets
Glutaraldehyde properties
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
What is the advantage of ortho-phthalaldehyde (OPA) over aldehyde?
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)
What are the properties of Ortho-phthalaldehyde (OPA)?
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
What are two Biguanides (antiseptic, disinfectant)?
Chlorhexidine
Alexidine
What is Biguanide mechanism of action?
Damage membrane + cytoplasm by:
- Damage cell membrane by reacting with the negatively charged groups on cell membrane, alter its permeability (FYI details)
- Crosses the cell outer membrane by passive diffusion
- Attack bacterial cytoplasmic or inner membrane OR the yeast plasma membrane
*cause coagulation or gelling of the cytoplasm
What is Biguanide (disinfectant, antiseptic) spectrum of activity?
Biguanides have broad spectrum of activity.
Limited effectiveness against virus
Not sporicidal, mycobactericidal, or fungicidal
What factors may affect Chlorhexidine activity?
- pH
pH dependent, only function in limited range of pH 5-7 - Easily inactivated by organic matter
Activity greatly reduced in presence of organic matter (either due to complexation or reduced amount of agent at site) - Easily inactivated by soups and detergents:
- Incompatible with soaps, detergents and other anionic materials as Chlorhexidine salts are cationic in solution - Surfactants:
- Compatible with cationic and nonionic surfactants
- In high conc. of surfactants, micellar binding may reduce Chlorhexidine activity
How does Alexidine differ from Chlorhexidine in terms of chemical structure?
What does this confer?
Alexidine possess ethylhexyl end groups
- This confers faster onset of bactericidal activity, produces faster alteration in bactericidal permeability
- Alexidine produces lipid phase separation which causes apoptosis via destruction of bacterial membrane
What are the 3 disinfectants that release chlorine?
- Hypochlorites
- Chloramine
- Sodium dichloroisocyanurate (tablets)
What is hypochlorite MOA?
Oxidation of sulfhydryl enzymes and amino acids
Ring chlorination of amino acids
Inhibition of protein synthesis
DNA disruption
Loss of intracellular contents
What is hypochlorite spectrum of activity?
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
What factors affect Hypochlorite activity?
- 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) - Activity is greatly reduced by presence of organic matter
Chemical inactivation by organic matter
