IC6 Types of Disinfectants Flashcards
Sterilization vs Disinfection vs Antisepsis
Eliminate all microbial life (Sporicidal)
Eliminate most life (Non-sporicidal) on inanimate surfaces
Eliminate most life (Non-sporicidal) on living tissue
What factors affect the efficacy of disinfection and sterilization?
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
Why is cleaning using water with detergent or enzymatic products an important factor affecting disinfection and sterilization?
Inorganic and organic materials that remain on the surfaces of instruments interfere with the effectiveness
Why must the location of microorganisms be considered when factors affecting the efficacy of germicides are assessed?
Direct contact of disinfectant and microbe
Why is preliminary cleaning important?
It increases the margin of safety
It shortens the exposure time required to kill the entire microbial load.
Why is preliminary cleaning important?
It increases the margin of safety
It shortens the exposure time required to kill the entire microbial load.
Why is preliminary cleaning important?
It increases the margin of safety
It shortens the exposure time required to kill the entire microbial load.
Which 3 microbes generally have greater innate resistance to chemical germicides? What is the mechanism of resistance?
- Spores - Spore coat and cortex barrier
- Mycobacteria - Waxy cell wall
- Gram negatives - Outer membrane barrier to disinfectant uptake
What is the relation between concentration and efficacy?
Non-linear positive correlation - More concentrated and potent, more efficacious, shorter exposure time
4 physicochemical factors affecting disinfectant efficacy
- Temperature - Increase activity but can cause degradation
- pH - Increase in glutaraldehyde, QAC but decrease in phenols, hypochlorites, iodine
- Relative humidity for gaseous disinfectants (Ethanol, formaldehyde)
- Water hardness - Divalent cations cause insoluble precipitates
2 ways that organic matter (serum, blood, pus) interfere with antimicrobial activity of disinfectants
- Chemical reaction with germicides - Form complexes that reduce activity
- Physical barrier - Protection by occlusion in salt crystals
What mechanisms of resistance can microbes that are within biofilms have?
- Older layers of biofilms (Physical)
- Genotypic variation
- Neutralizing enzyme production
- Physiologic gradients within biofilm
What are biofilms?
Thick masses of cells and extracellular materials tightly attached to surfaces, difficult to remove
Biofilms are treated with ______________
Chlorine compounds and ozone
List of Chemical Disinfectants
(2ABCDE PIP 2 Metal QAC)
- Alcohols (Ethanol, isopropanol)
- Aldehydes (Formaldehyde, Glutaraldehyde, Ortho Phthalaldehyde)
- Biguanides (Chlorhexidine, Alexidine)
- Chlorine compounds (Hypochlorite, Chloramine, Sodium dichloroisocyanurate)
- Diamines
- Eucalyptus
- Phenols (Chloroxylenol)
- Iodine & Iodophors (Povidone-iodine)
- Peroxygens (H2O2) & Peracetic acid
- Silver Sulfadiazine
- Mercuric Chloride
- Quaternary Ammonium Compounds (Benzalkonium chloride)
Alcohol uses and in what instance not recommended and why?
- Disinfection (Hard surface)
- Antisepsis (Skin)
- Not recommended for surgical material (Non-sporicidal)
What is alcohol’s MOA and what increases its MOA?
- Bactericidal - Denaturation of proteins
- Require water
- Bacteriostatic - Inhibition of metabolite production
What are the limitations of ammonia? What can be done to overcome?
- Eye and GI irritation
- Toxic when mixed with bleach
- Corrosive => Wear PPE
Ammonia is used for ______
Cleaning many surfaces (Glass, Stainless steel)
Which alcohol kills bacteria and non-enveloped viruses and which kills enveloped viruses
Isopropanol kills bacteria and non-enveloped viruses (More viscous)
Ethanol kills enveloped viruses
Ammonia MOA?
Saponify lipids within enveloped microbes forming precipitation of salt complexes
What are some limitations of aldehydes?
Toxicity issues, odour and carcinogen potential
Aldehyde MOA?
The biocidal activity of aldehydes results from alkylation of sulfhydryl, hydroxyl, carboxyl and amino groups of microorganisms, which alters RNA, DNA and protein synthesis.
Spectrum activity of aldehydes?
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
Uses of different aldehydes
Sterilant (Formaldehyde - Sporicidal)
High-level Disinfectant (Both Formaldehyde and Glutaraldehyde)
Formaldehyde - Viral vaccines prep
Glutaraldehyde - Medical equipment
Paraformaldehyde - Laminar flowhood
OPA uptake, MOA, Spectrum activity
Uptake through outer layer due to lipophilic aromatic nature
Cross-linking agent to amino acids, protein, DNA
Sporicidal, Mycobacteria, Gram negatives
OPA - What type of disinfectant, advantage and disadvantage?
High-level disinfectant
Advantage - pH stable; less eye and nose irritation, and odour, only need 5 min contact time
Disadvantage - Gray staining on skin
Biguanide spectrum activity? Bacteria? Viruses? Spores?
Broadspectrum bactericidal
Limited against viruses
Non-sporicidal
Biguanides MOA? (Chlorhexidine and Alexidine)
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
What factors affect biguanide disinfectant efficacy?
Organic matter and cleaning soap reduce efficacy
Chlorine compounds MOA?
- Oxidation of Sulfhydryl enzymes & AA
- Ring chlorination of AA
- Protein synthesis inhibition
- DNA disruption
- Intracellular content loss
Advantage of using chlorine compounds? (Spectrum? Toxicity? Physical factors & efficacy? Cost?)
Broad spectrum, non-toxic, not affected by water hardness, useful against biofilms, cheap
Disadvantage of chlorine compounds? (For users? Factors affecting efficacy?)
- Eye and GI irritation
- Metal corrosiveness
- Organic matter inactivation
- Toxic gas is released
What factor increases hypochlorite activity?
pH increase allows less conversion of HOCl to OCl
Which chloride compound retains chlorine longer to exert longer effects?
Chloramine
Which chlorine compound is in tablet form and why?
Sodium dichloroisocyanurate
When free chlorine is used up, equilibrium can be restored since only 50% of total chlorine is free
Iodine and Iodophor MOA?
Penetrate cell wall quickly and disrupt protein & nucleic acid structure & synthesis
Iodine and Iodophors are used as _____
Antiseptic for Skin and Tissue (Iodine)
Antiseptic and disinfectant for medical equipment (Iodophors)
What are iodophors made up of and their purpose?
Solubilizing agent with iodine to provide a sustained release reservoir for free iodine
How does dilution affect Iodophors?
The linkage between iodine and solubilizing agent
Peroxygen (H2O2) MOA?
Oxidant producing free radicals attack membrane lipids and DNA
H2O2 is used for _____ and spectrum activity covers _______
Disinfection, Sterilization, Antisepsis
Bactericidal, Sporicidal (At high conc)
How do surfactants, chelating agents and emulsifiers accelerate H2O2 activity?
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
Peracetic acid MOA
Denature proteins and enzymes and increases cell wall permeability by disrupting sulfhydryl (-SH) and sulfur (S-S) bonds.
Advantage of peracetic acid
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.
Main application of peracetic acid
Low temperature liquid sterilant for medical devices and environmental surface sterilant.
Phenol MOA?
Phenol induces progressive leakage of intracellular constituents, including the
release of K+, which it usually is the first index of membrane damage.
Phenol spectrum activity?
Antifungal (damage to the plasma membrane) and antiviral properties.
Chloroxylenol MOA?
Disruption of microbial cell walls and inactivation of cellular enzymes.
Chloroxylenol - How toxic?
Relatively nontoxic and nonirritant material when used as an excipient in topical products, but it is toxic upon oral consumption or eye contact.
Diamidine MOA?
Inhibition of oxygen uptake and leakage of amino acids.
Example of diamidine and uses
Propamidine
Bacteriostatic agents for the topical treatment of wound.
Silver sulfadiazine Spectrum activity
Antibacterial agent combination
Mercuric chloride MOA?
Broad range disinfectant, which affect microbial peptide synthesis.
Mercuric chloride cautions?
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.
QAC MOA?
(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.
Why are QAC sometimes called cationic detergents?
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).
Are QAC sporicidal?
No
When do we use vapor phase sterilants? Other than vapor phase sterilants, what else can be used?
Heat-sensitive medical devices and surgical supplies
Liquid sterilants (Glutaraldehyde, peracetic acid, H2O2)
Vapor sterilants include
Ethylene oxide and formaldehyde
Safety differences for the vapor sterilants
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)
What is infectious dose?
Minimum amount to cause infection
