Chemical anti-microbial agents are divided into what general types? (10)
A. Phenols and phenolics
E. Oxidizing agents
G. heavy metals
H. Food and cosmetic preservatives
J. Gaseous Agents
How do chemical anti-microbial agents kill microbes?
They kill microbes by damaging their cytoplasmic membrane, proteins, DNA or cell walls
What does the killing effectiveness of anti-microbial agents depend on?
Their killing effectiveness depends on the type of antimicrobial agent, temperature, length of exposure, amount of organic matter present, pH, and the concentration and age of the antimicrobial solution.
Chemical anti-microbial agents are more effective against what?
Chemical anti-microbial agents are more effective against lipid enveloped viruses & the vegetative cells of bacteria, protozoa and fungi than they are against endospores, naked viruses or protozoan cysts.
What are antimicrobics?
antibiotics, semi-synthetic antibiotics & synthetic chemicals that are used to control microbial growth in the body of a host. Some antimicrobics are used for antimicrobial control outside of the body.
An ideal chemical antimicrobial agent should be:
2. Fast acting
3. Stable during storage
4. Not affected by the presence of organic material
5. Compatible with soaps, detergents, and other chemicals
6. Able to control all microbial growth while being harmless to humans, animals and objects.
Do chemical antimicrobials achieve sterility?
Few chemical antimicrobials achieve sterility. Their primary use is to kill vegetative pathogens and reduce the numbers of microbes in the environment, food, water and living tissue to safe levels.
Each chemical antimicrobial agent differs in:
1. Its mechanism of action
2. The types of microbes it will kill
3. The time and conditions under which it kills
4. The types of objects on which it can be safely used
In order to select an appropriate chemical antimicrobial agent to use, it is essential to know:
1. The properties of the chemical antimicrobial agent
2. The types of microbes the antimicrobial will kill
3. How long it takes the antimicrobial to kill them
4. Whether the chemical antimicrobial agent is designed to disinfect the material being disinfected.
What information will the manufacturer's directions on the disinfectant bottle give?
The correct concentration, temperature, and application time for using the disinfectant, and how long the diluted disinfectant can be stored
What four methods can be used to evaluate the effectiveness of disinfectants in killing microbes?
1. The phenol coefficient
2. Use dilution tests
3. Filter paper disk diffusion methods
4. In-use tests
In the past, what standard for determining the killing efficacy of various disinfectants was used?
Comparing their killing efficacy to that of phenol, and report the results as the phenol coefficient. This method does not work well for agents that are bacteriostatic or have residual activity on surfaces.
What is the current standard for evaluating the efficacy of disinfectants is the
The current standard for evaluating the efficacy of disinfectants is the American Official Analytical Chemist's use-dilution method
What are the three standard test microbes used for the phenol coefficient and use-dilution tests?
1. Staphylococcus aureus
2. Salmonella choleraesuis
3. Pseudomonas aeruginosa
What are the first 2 steps to the Phenol Coefficient test?
Microbes in broth cultures are exposed to various concentrations of phenol or the disinfectant being tested for a specified time. A sample is then transferred into fresh culture medium to see if all of the microbes were killed by the disinfectant
What are the last two steps of the phenol coefficient tests?
The efficacy of the test disinfectant is compared to that of phenol and expressed as a ratio called the phenol coefficient. If the disinfectant is more effective than phenol in killing microbes, its phenol coefficient will be greater than one.
What is used for a use-dilution test?
The use-dilution test employs metal rings that have been allowed to absorb live bacteria
What are the steps to the use-dilution tests?
1. The metal rings are placed in fresh bacterial cultures for 10 minutes so that bacteria can adhere to them.
2. The rings are removed and dried on sterile filter paper
What are the steps to the use-dilution tess? 2
3. The bacterial samples are placed in test tubes containing various dilutions of disinfectant for 10 minutes
4. The rings are removed from the solution, placed in sterile media, and incubated at 37C to determine if all the bacteria was killed
What is an acceptable use-dilution?
An acceptable use-dilution is one that kills the test microorganism at least 95% of the time.
How are filter paper disk diffusions carried out?
They are done by dipping a filter paper dik into a solution of an antimicrobial agent, and then placing the disk onto the surface of an agar medium inoculated with a test microbe.
What is an in-use test?
Sterile swabs or contact plate are used to sample objects and surfaces before an after application of a disinfectant. Each swab sample is inoculated onto the surface of an agar medium, and the agar plates monitored for the growth of bacterial colonies
What are the advantages and disadvantages of an in-use test?
In use tests provide an accurate measure of how effective a disinfection procedure has been, but are more expensive and time consuming to cary out than the other tests that were described.
What are the EPA's 3 efficacy levels for chemical disinfectants?
The environmental protection agency categorizes disinfectants into three efficacy levels: High, intermediate and low, according to the type of microbes they kill
What is high level disinfection?
High level disinfection is the same as sterilization; it kills (or inactivates) all life forms
What is intermediate level disinfection?
Intermediate level disinfection kills all life forms except endospores
What is low level disinfection?
Low level disinfection kills vegetative gram-positive bacteria, vegetative gram-negative bacteria and lipid enveloped viruses, but not mycobacteria, endospores, non-lipid viruses and some fungi
Describe the CDC's system for classifying chemical disinfectants
3. Hospital Level Disinfectant w/ HIV, Hep B & Hep C activity will kill those viruses but not mycobacteria
What was the first chemical used to disinfect surgical wounds? Is it still used?
Phenol (carbolic acid)
It is rarely used now because it has an unpleasant odor, is irritating to skin & mucous membranes, and is toxic
What are phenolics?
Phenolics are chemical derivatives of phenol. Examples are o-phenylphenol (Lysol), orthocresol and amylphenol (Amphyl)
What disinfectant level do phenolics fall under?
Phenolics are intermediate to low level disinfectants that are less irritating and toxic to humans than phenol. They are effective in killing mycobacteria but do not always inactivate naked viruses.
How do phenolics work?
Phenolics kill cells by damaging their plasma membrane and denaturing proteins
Why are phenolics usually dissolved in a detergent solution?
It enhances their ability to wet surfaces
What effect do organic compounds have on phenolics?
Phenolics remain active in the presence of organic compounds, so they are effective in disinfecting blood, pus, saliva, feces, and other body fluid spills
Are phenolics stable to dilution?
Phenolics are stable to dilution and remain active on surfaces for long periods after application.
What are phenolics commonly used for?
They are commonly used for disinfection in health care facilities, labs and homes
What are the primary disadvantages of using phenolics for disinfection?
1. Some people dislike the odor
2. They irritate the skin of some individuals and can accumulate to toxic levels
3. They require ten minutes contact time to kill microbes
What are bisphenols?
Derivatives of phenol that contain 2 phenolic groups. They are intermediate to low level disinfectants.
What two bisphenols are commonly used as disinfectants?
Hexachlorophene and triclosan.
What is hexachlorophene especially effective in killing?
staphylococci and streptococci
It is used as a surgical scrub and to control skin infections in hospitals. It is available through prescription only because it can cause neurological damge if overused
What is triclosan used for?
Triclosan is widely used in commercial antibacterial soaps, toothpaste, kitchen cutting boards, pillows, etc
What level of disinfection are Biguanides?
Bigaunides are low level disinfectants that are used to disinfect skin and mucous membranes. They are not structurally related to phenolics or bisphenols.
What is chlorhexidine?
Chlorhexidine is the best known biguanide that kills vegetative microbes by disrupting their plasma membrane and is especially effective in killing staphylococci and streptococci
Describe the availability of chlorhexidine?
It is available in the US by prescription only and is commonly used as a surgical scrub and in a prescription mouthwas called Peridex
What are halogens?
Reactive non-metallic elements iodine, chlorine, fluorine, and bromine. They are effective intermediate level disinfectants in their pure elemental state and in compounds with other elements
What is iodine used for?
Iodine has long been used as an antiseptic for skin and wounds. It kills microbes by combining with tyrosine groups in proteins, which inactivates the protein. It can be used as a tincture or an iodophor.
What is a tincture?
Iodine dissolved in 70% alcohol instead of water
What is an iodophor?
An iodophor is an organic molecule-iodine complex that releases Iodine slowly
Compare Iodine tinctures to iodophors
Iodine tinctures are irritating to skin and can stain objects and materials. Iodophors do not stain and are less irritating to skin that iodine tinctures, so iodophors are usually preferred to iodine tinctures
What are common iodophors used for skin disinfection?
Betadine and isodine are iodophors that are commonly used for skin disinfection. They contain the iodine-binding organic molecule povidine, which is also a surface wetting agent
What common iodophors are used for disinfection of hard surfaces?
Wescodyne, Iodofive and biocide are examples of iodophors that are used for disinfection of hard surfaces.
What disinfection level are Iodophors?
Iodophors are EPA registered as intermediate level disinfectants. They are one of four general types of disinfectant recommended by the epa for surface disinfection in medical and dental facilities
What are the disadvantages of using iodophors and iodine solutions for disinfection?
1. Diluted solutions lose iodine at a slow constant rate, and have a shelf life of only 1-2 weeks
2. Inactivated by the presence of organic matter
3. Pseudomonas species and protozoan cysts are resistant
4. Require 10 min contact time to kill microbes
What disinfectant level is chlorine and chlorine compounds
Chlorine and chlorine compounds are highly effective intermediate level disinfectants capable of high level disinfection.
What is chlorine?
Chlorine is a gas that combines with water to form hypochlorous acid, which readily enters cells, and is a potent oxidizing agent that destroys proteins, lipids and nucleic acids, killing the cell
What is chlorine gas commonly used for?
Chlorine gas is commonly used by municipalities to disinfect drinking water
What are the disadvantages of using chlorine to disinfect drinking water?
1. Protozoan cysts are resistant to the chlorine levels commonly used in drinking water. They have to be removed by filtration.
2. Chlorine combines with organic matter in drinking water and forms carcinogens
Is chlorine gas toxic?
Chlorine gas is extremely toxic and corrosive. Less toxic. more convenient forms of chlorine are commonly used for routine disinfection.
What is bleach?
Five percent sodium hypochlorite is called bleach. It is a commonly used, inexpensive, highly effective household disinfectant for laundry and floors.
A 1/10 dilution is recommended by the EPA for disinfection of hard surfaces in medical facilities.
What are the effects of organic matter on bleach?
A 1/10 dilution of bleach is not affected by the presence of large amounts of organic material and gives intermediate level disinfection in 5 minutes
What are the disadvantages of using bleach for disinfection?
1. It is highly corrosive for fabrics, aluminum and some other metals.
2. It is irritating to mucous membranes
3. It must be removed from sensitive materials by washing it off with water
What is calcium hypochlorite?
A solid form of chlorine that forms hypochlorous acid when mixed with water (lime water). It is commonly used to disinfect equipment and floors, especially in agriculture
What level of disinfection do alcohols fall under?
Ethanol and isopropanol are considered to be intermediate level disinfectants in 50-95% concentrations in water. They kill vegetative microbes but have little activity against naked viruses and fungal spores
How do alcohols kill microbes?
Alcohols kill microbes by denaturing proteins, dissolving lipids and disrupting membranes.
How well does pure alcohol disinfect?
Pure alcohol is ineffective as a disinfectant because some water must be present for alcohol to denature proteins and disrupt cell membranes.
What is alcohol used to disinefect?
Alcohol is used to disinfect hard surfaces and skin, but are not recommended for use on wounds because they denature proteins important in wound healing
What are the primary disadvantages of using alcohol as a surface disinfectant?
It evaporates quickly when spread as a thin film, which can result in insufficient contact time with microbes and some people dislike the odor of alcohol.
What are alcohol antimicrobial solutions called?
Tinctures. It is commonly used in combination with iodine or a quarternary ammonium compound
How are Heavy Metals and their compounds antimicrobial?
The ions of heavy metals such as mercury, silver, zinc, lead and copper are germicidal in low concentrations because they denature proteins.
What effect does organic material have on heavy metals in relation to its killing efficacy?
The killing efficacy of heavy metal ions is reduced or destroyed by the presence of organic materials.
What are surfactants?
Surfactants are surface active agents such as soaps, anionic detergents and cationic detergents that decrease the surface tension properties of water.
What are soaps?
Sodium salts of fatty acids
How effective are soaps as antiseptics?
Soaps are NOT effective antiseptics or disinfectants because they do not kill most microbes. Yet, hand washing with soap is known to be on of the most effective ways of preventing cross infections between personnel and patients in hospitals
Why are anionic detergents stronger surfactants than soap?
They contain a sulfonic acid group at the end of a hydrocarbon chain instead of a carboxyl group
Why are anionic detergents poor disinfectants?
They are ineffective in killing many gram-negative bacteria
What are quaternary ammonium compounds?
Cationic detergents, commonly called quats, that have a cationic quaternary ammonium group at one end of a long hydrocarbon chain.
What are the most common Quats?
Cepacol and Zephiran
What are the advantages of quats?
They are good sanitizers and good surfactants. They are odorless, tasteless, non-toxi and are commonly used in toothpastes, mouthwashes, body powders, and many other products.
What are the disadvantages?
Quats are poor disinfectants by themselves. Using a tincture is more effective.
Organic matter, soaps and detergents interfere with their action; they are ineffective against pseudomonas, many other gram negative bacteria and naked viruses
What disinfection level are quats rated?
Quat tinctures are considered to be intermediate level disinfectants. They are EPA recommended for disinfection of hard surfaces in medical and dental facilities, but have little activity against naked viruses.
Why are quats used as popular surface disinfectants?
They disinfect in five minutes, are non toxic, have good wet ability and do not need to be wiped up after applying.
How do quats kill microbes?
Quats kill microbes by disrupting the cell membrane and denaturing proteins
What are organic acids and their salts commonly used for?
Preservatives in foods, cosmetics, and soft drinks
What are sorbic acid and potassium sorbate used for?
the inhibition of mold growth in acidic foods
What are aldehydes?
Organic compounds that contain a carbonyl end group. They are highly reactive chemicals that are capable of high level disinfection.
What are the most commonly used aldehyde disinfectants?
Formaldehyde and glutaraldehyde
What is formaldehyde?
A water soluble gas that is sold as a 37% solution in water called formalin. It is commonly used tp [reserve biological specimens and cadavers. It is volatile, irritating to mucous membranes, allergenic and carcinogenic.
What is glutaraldehyde commonly used for?
Disinfect contaminated medical/dental instruments before they are cleaned and sterilized.
Cold sterilize instruments that cannot be autoclaved
How long will a 2% solution of glutaraldehyde take to be bacteriocidal? sporicidal?
sporicidal- 10 hours
What are the primary disadvantages of using glutaraldehyde to sterilize?
The long time required to achieve sterilization. It must be rinsed from instruments with water before the instrument can be used. It is highly allergenic and carcinogenic if it contacts skin
What are gaseous chemosterilizers?
gases such as ethylene oxide, propylene oxide, β-propiolactone and chlorine dioxide that can sterilize items in a closed chamber at room temperature.
What are the disadvantages of gaseous chemosterilizers?
They require 18 hours to sterilize and 24 hours of ventilation afterwards. Their fumes are highly irritating, allergenic, poisonous and carcinogenic.
What are oxidizing agents?
chemicals such as peroxides, ozone and peracetic acid that are intermediate to high level disinfectants that kill microbes by denaturing proteins, destroying lipds and breaking DNA molecules
What is ozone?
a highly reactive form of oxygem that is formed from O2 by high voltage electrical discharges, lightning, and UV light
What is hydrogen peroxide?
It quickly kills bacterial cells and is a good disinfectant/sterilizer for inanimate objects (contact lenses) and surfaces.
What are oxidizing agents especially effective against?
obligate anaerobes. They are used to irrigate deep wounds to try to prevent clostridia and other obligate anaerobes from growing in the wound and causing gas gangrene
What is one problem that occurs with high usage of antimicrobials?
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