Antiseptics and Disinfectants Flashcards
What do antiseptics and disinfectants have in common?
Antiseptics and disinfectants are nonselective, anti-infective agents that are applied topically.
Describe antiseptics
Antiseptics are chemical substances which inhibit the growth or kill micro-organisms on living surfaces such as skin & mucous membrane.
In general, antiseptics are applied on tissues to suppress or prevent microbial infection
What are antiseptics applied to the skin or oral mucosa used for? Give example
Antiseptics applied to the skin or oral mucosa have a local action, they are not absorbed as in case of ATB.
For example, they are useful against bacteria found on the teat but not against bacteria in the milk ducts and mastitis infection. (ATB have to be used).
Describe disinfectants
The term “disinfectant” is applied to chemical agents which kill or prevent the multiplication of microorganisms. Most of them rapidly kill bacteria (within few minutes) in contrast with the antibiotics.
Disinfectants kill naked virus and spores e.g. chlorine, glutaraldehyde; microbicidal bacteria and fungi: vegetative form (actively growing); spores form (static form).
Disinfectants are germicidal compounds usually applied to surfaces.They are too toxic at used concentration to be applied to the body
When can the same compound act as an antiseptic and a disinfectant?
Sometimes the same compound may act as an antiseptic and a disinfectant, depending on the drug concentration, conditions of exposure, number of organisms, etc. To achieve maximal efficiency, it is essential to use the proper concentration of the drug for the purpose intended.
Describe the ideal properties of a good antiseptic or disinfectant
1) It should be rapidly effective
2) It should be active against all pathogens (bacteria, viruses, fungi) -
cidal
3) It should not allow the development of resistant bacteria
4) It should not be inactivated by protein (active in presence of pus, blood
& exudates)
5) It should be minimally toxic for animal
6) It should be non-staining and non-corrosive
7) It should not harm the skin - non irritating to tissues / non sensitizing
8) It should be odourless and deodorizing
9) It should possess residual action after rinsing
10) It should have detergent properties
11) It should be simple and economical to use
Describe the mechanisms of action of antiseptics and disinfectants
- Oxidation of bacterial protoplasm – Potassium permanganate, H202, halogens
- Coagulation (denaturation) of bacterial proteins by disrupting hydrogen and disulfide bonds in cell membrane – phenols, chlorhexidine, alcohols, aldehydes.
- Detergent like action ↑ permeability of bacterial cell membrane – soaps.
- Competition with essential substrates for important enzymes in bacterial cell.
Division of oxidizing agents
- those which release gaseous oxygen (the peroxides)
- those which cause oxidation without the release of oxygen gas (the halogens)
- potassium permanganate
Name all the peroxides
Hydrogen peroxide solution, Peracetic acid, Benzoyl peroxide
What is hydrogen peroxide solution and it’s mechanism of action?
is an aqueous solution of H2O2 in a 3% concentration.
- liberates oxygen when in contact with catalase present on wound surfaces and mucous membranes
It has 2 fold action:
- oxidizing effect (antibacterial) of the nascent oxygen produced in contact with organic tissue (due to the presence of enzyme catalase: H2O2->H2O + O)
- mechanical cleansing action due to the rapid release of O
These actions persist only as long as oxygen is being produced (no bubbling-no activity).
Use of hydrogen peroxide solution.
The effervescent action mechanically helps remove pus and cellular debris from wounds and is useful to clean and deodorize infected tissue.
It is used also upon the mucosa
Describe the combination of peracetic acid and hydrogen peroxide solution (the benefits)
Peracetic acid and the combination of peracetic acid and hydrogen peroxide have been recognized as useful sterilants and antiseptics, combining the broad antimicrobial spectrum and lack of harmful decomposition products of hydrogen peroxide with greater lipid solubility and freedom from inactivation by tissue catalase and peroxidase.
They can be used over wide temperature (0o–40oC) and pH ranges and are not affected by organic matter.
Use of peracetic acid solution and hydrogen peroxide solution
They are effective against bacteria, yeasts, fungi, and viruses at concentrations of 0.001–0.003% and is sporicidal at 0.25–0.5%.
Solutions of 0.2% peracetic acid applied to compresses are effective at reducing microbial populations in severely contaminated wounds.
Describe benzoyl peroxide’s activity and use
Benzoyl peroxide slowly releases oxygen to act as an antiseptic. However, it can cause skin irritation. It also has keratolytic and antiseborrheic activity, which makes it useful in treating pyoderma in dogs.
Name the halogens
Chlorine, hypochlorites, iodine
Describe the halogens
They are still used as topical antimicrobial agents to some degree.
They are inexpensive, rapidly bactericidal and of broad spectrum activity.
Halogen mechanism of action
They owe their activity to high affinity for protoplasm, where they are believed to oxidize proteins and interfere with vital metabolic reactions.
Describe chlorine and it’s use
It is a strong oxidizing agent
It is used in disinfection of water and liquids.
Chlorine exerts a potent germicidal effect against most bacteria, viruses, protozoa, and fungi at concentration 0.1 ppm but higher concentrations are needed in the presence of organic matter
It also has deodorizing properties.
It is widely used to disinfect water supplies and inanimate objects (eg, utensils, bottles, pipelines) in dairies, creameries, and milk houses.
In 200 ppm concentration in drinking water (it is common conc.) has an antiviral activity
Chlorine mechanism of action
formation of undissociated hypochlorous acid (HOCl) in water at acid to neutral pH.
Cl2 + H2O -> HOCl +H+ + Cl-;
HOCl -> O is released gradually.
Therefore, is a strong oxidizing agent
What can reduce chlorine activity?
Alkaline pH ionizes chlorine and decreases its activity by reducing its penetrability.
Drawbacks of chlorine
Chlorine has a strong acid smell and is an irritant to the skin and mucous membranes.
It is extremely toxic= even in low concentration may be dangerous.
Name the hypochlorites
Sodium hypochlorite solution (bleach) and Chlorinated lime (chloride of lime)
Describe hypochlorites generally
They are slowly releasing chlorine when exposed to atmosphere or to organic material. They are unstable, therefore are of short duration of action. By the light are decomposed quickly.
Use of sodium hypochlorite solution (bleach)
It is an inorganic chloride.
It is recommended for the use as a teat dip for mastitis control, NaOCl solution can be used as a disinfectant and a more diluted form can be used for irrigating suppurating wounds, but it dissolves blood clots and delays clotting.
Use and mechanism of action of chlorinated lime
It contains Na and Ca chloride.
It decomposes slowly and releases chlorine when is in contact with CO2.
It is a powerful disinfectant as long as free Cl2 is available.
It is used on drains, buildings etc.
Disadvantages of using hypochlorites
It bleaches most dyes (cloth).
Hypochlorites when exposed to organic material form chloramines by combining with amino groups.
Chloramines are slowly and mildly antiseptic due to slow release of Cl2.
All chlorine releasing agents are rapidly inactivated by the presence of organic matter (soil, faeces, etc.).
Name all the forms of iodine used
Iodine, iodine tincture, aqueous solution of iodine ( Lugol’s Solution), iodophores
Describe iodine and its use
Elemental iodine is a potent germicide with a wide spectrum of activity and low toxicity to tissues.
It is poorly soluble in water but readily dissolves in ethanol, which enhances its antibacterial activity.
Although it is used from 1839 still belongs among the most important disinfectants.
Depending on the concentration it has bactericidal, virocidal, sporocidal and fungicidal activity.
Disadvantage of using iodine
Iodine is used in dilute solutions, but is an irritant and retards healing.
Iodine tincture use
skin disinfectant
Use of aqueous solution of iodine ( Lugol’s Solution)
used mainly for intrauterine and vaginal irrigation after dilution
What are iodophors?
Iodophors are complexes of iodine with a surface-active agent such as polyvinyl pyrrolidone
They retain the activity of iodine.
They kill vegetative bacteria, mycobacteria, fungi, and lipid-containing viruses. They may be sporicidal upon prolonged exposure.
They are nontoxic to tissues and often change colour when their activity is lost ( are effective as long as the brown colour remains)
Use of iodophors
They slowly release iodine as an antimicrobial agent and are widely used as skin disinfectants, particularly before surgery and in mastitis-control programmes for udder washing before milking and teat dipping after milking.
Potassium permanganate use and disadvantage
Solutions are antiseptic and adstringent.
Potassium permanganate has broad antimicrobial properties, but its intense purple colour in solution, which stains tissues and clothing brown, is a disadvantage (in contact with tissue is decomposed quickly - the solution turns to brown and it is ineffective).
It is an effective algicide and virucide for disinfection. It’s used also as a wound and mouth lotion.
Name the reducing agents
formaldehyde, glutaraldehyde, ortho-phtalaldehyde
Compare and describe formaldehyde and glutaraldehyde
Formaldehyde is a gas, whereas
glutaraldehyde is an oil at room temperature.
Their solutions are irritating or caustic to tissues but have potent germicidal properties against all organisms, including spores. Their solutions do not lose appreciable antimicrobial properties in the presence of organic matter.
Have a broad spectrum of activity against microorganisms and viruses.
Use and mechanism of action of formaldehyde and glutaraldehyde
They are primarily used as fumigant antiseptics.
Action: They act by alkylation of chemical groups in proteins and nucleic acids.
Describe formaldehyde use more in detail
It is an irritant gas with antiseptic and adstrigent action.
Diluted in water forms „Solution of formaldehyde“ known as formalin, which contains 40% of formaldehyde.
Its main external action is as a fumigant disinfectant or as an aqueous disinfectant spray.
The rooms should be fumigated and closed for 10 hours. Spraying water prior to fumigation assists the action.
Describe glutaraldehyde use more in detail plus its disadvantage
The solution must be alkalinized for activation.
Activated solutions are bactericidal, sporicidal, fungicidal, and virucidal for both lipophilic and hydrophilic viruses. Glutaraldehyde has greater sporicidal activity than formaldehyde.
It is often used to sterilize surgical and endoscopic instruments and plastic and rubber apparatus.
It is a known sensitizer, causing occupational contact dermatitis, as well as bronchial and laryngeal mucous membrane irritation.
Describe ortho-phtalaldehyde and compare it to glutaraldehyde
is a phenolic dialdehyde chemical sterilant with a spectrum of activity comparable to glutaraldehyde, although it is several times more rapidly bactericidal.
Is less toxic and irritating to eyes and nasal passages, and has a barely perceptible odour.
OPA solutions are faster acting than glutaraldehyde against mycobacteria but have somewhat less sporicidal activity.
High-level disinfection can be achieved much faster than with glutaraldehyde.
Unlike glutaraldehyde, OPA requires no activation and is less irritating to mucous membranes.
Name the acids
acetic acid, acetic acid mixed with hydrogen peroxide, boric acid
Describe acid mechanism of action
Hydrogen ion is bacteriostatic at pH ~3–6 and bactericidal at pH <3. Unionized weak organic acids can readily penetrate and disrupt bacterial cell membranes.
Describe acid use
Acids are used as food preservatives (eg, benzoic acid), antiseptics (eg, boric acid, acetic acid), fungicides (eg, salicyclic acid, benzoic acid), spermatocides (eg, acetic acid, lactic acid), and cauterizing agents (strong mineral acids).
Acetic acid use
can be used in surgical dressings and is a useful antibacterial agent for irrigation of the urinary tract.
Itis bactericidal to many bacteria and has been used to treat otitis externa produced by Pseudomonas, Candida, Malassezia, or Aspergillus spp.
What is acetic acid mixed with hydrogen peroxide called and used for?
It’s so called peracetic acid and is one of the best disinfectants against spores.
Boric acid use
a weak acid for irrigating the conjunctival sac, but it has only a limited antibacterial action
Name the alkalies
Sodium hydroxide, sodium carbonate, calcium hydroxide
Alkalie use
Hydroxyl ion also exerts antimicrobial activity. Most bacteria are inactivated above pH 9, but above pH 13 they have antiviral activity (e. g. in foot- and mouth disease), what is a great advantage of the alkalies.
Hydroxides of sodium and calcium are used as disinfectants.
A solution of soda lye in hot water is used as a disinfectant against many common pathogens, such as those causing fowl cholera and pullorum disease.
On the skin solution NaOH is recommended. When used in hot solution its activity is higher.
They are potent caustics and must be handled with care.
Name the alcohols
Ethanol and isopropyl alcohol (isopropanol)
Describe the alcohols
Frequently used for antisepsis and disinfection
They are rapidly active, killing vegetative bacteria, Mycobacterium tuberculosis (less against staphyloccoci), and many fungi and inactivating lipophilic viruses.
Alcohol mechanism of action
Antimicrobial effect is related to their lipid solubility (damages bacterial membranes) and their ability to precipitate cytoplasmic proteins. However, they do not destroy bacterial spores.
Describe use of ethanol
is often used for the disinfection of skin (pre-injection).
In higher concentration than 70% it is too irritant the skin and mucosa (protein precipitation).
Acid alcohol is effective in inactivating bacterial spores.
Isopropanol use
is slightly more potent than ethanol because of its greater depression of surface tension.
“Rubbing alcohol” is a mixture of alcohols, with isopropanol as its principal ingredient. It is used as a skin disinfectant and rubefacient
Phenols and Cresols use
Are rarely used anymore. However phenol is still used as the standard by which other disinfectants are judged.
Hexachlorophene use
Hexachlorophene (a phenol) has a strong bacteriostatic action against many gram-positive organisms (including staphylococci) but only a few gram-negative ones.
It is used widely in medicated soaps. Frequent washings every day with hexachlorophene soaps lead to sufficient retention of residue on the skin to provide prolonged bacteriostatic action. Washing with other soaps promptly removes these residues.
Pine tar use
Pine tar is a viscid blackish brown liquid, used primarily for antiseptic bandaging of wounds of the hoof and horn.
Pine tar contains phenol derivatives that provide antimicrobial properties.
Name some phenols that are used.
Hexachlorophene and pine tar
Name the dyes
There are two types:
Azo dyes ex. scarlet red
Acridine dyes ex. acriflavine, proflavine, aminacrine
Azo dye use
Azo dyes (eg, scarlet red) are most active in an acidic medium and are effective against gram-negative organisms.
Describe acridine dyes, their use and mechanism of action
Are bacteriostatic antiseptics. They are mainly active against G+ pyogenic organisms because they possess only little activity against Gr- bacteria.
Their activity is enhanced in alkaline medium and antagonized by hypochlorites.
Antibacterial action is thought to be due to interference with the amino acid sequence of DNA.
What has acriflavine jelly been used extensively for?
acriflavine jelly have been used extensively for treatment of burns.
What are detergents?
They belong to the large group called surface active agents, which all have property of reducing surface tension, i. e. they are emulsifying agents and are commonly used for chemical cleansing (laundry). Some of detergents have stronger antibacterial properties than others, but the antibacterial activity is not related directly to the surface activity.
What are the 2 types of surface active agents?
- ionic detergents
- non-ionic or amphoteric detergents
Describe the ionic group of detergents and their division
- anionic detergents, which are active in mildly acid solution
- cationic detergent, which are active in alkaline solution
All anionic detergents are antagonized by cationic ones and vice versa.
The antibacterial activity of detergents is greatly reduced in the presence of organic matter such as blood, pus, serum etc.
Detergents have little or no effect on viruses, spores and fungi
Give an example of an anionic detergent and it’s use
An example of anionic detergent are soaps.
Their antibacterial activity is not great (only against Gr+) therefore antibacterial agents such as phenols, chlorohexidine should be incorporated with them to reach a stronger action.
Hard soap
In vet. field it is used as a lubricant enema or rectal suppository in the treatment of faecal constipation (impaction).
Mechanism of action of anionic detergents
Their cleansing properties are due to the emulsification of grease, dirt and similar debris to which bacteria are adherent.
Soaps remove the microorganisms mainly mechanically from the body surface.
Which bacteria are cationic detergents effective against?
G- and G+, but for G- a higher con. is needed
Give an example of a cationic detergent and its importance
Quaternary ammonium compounds
They are used as disinfectants for instruments and utensil, these should first be heat sterilized to destroy spores (cationic detergents have no effect upon spores). The quaternary ammonium detergents will maintain the sterility.
When applied on the skin, they form a film, which is strongly antiseptic externally only, but not internally, so that bacteria may exist under the film. To overcome this phenomenon is to include alcohol in the quaternary ammonium solutions.
List the most important quarternary ammonium compounds
Benzalkonium chloride
Carbenthopendecinium „Septonex“ Benzododecinium
What are amphoteric compounds and what are they used for generally?
They are surfactants possessing at least one anionic and one cationic group and so depending on the pH can have anionic or cationic properties. At pH above 7 they are anionic and bellow pH 7 cationic. At pH 7 the anionic and cationic parts of the molecule are of equal strength so these compounds have been widely used for both to clean and disinfect equipments and buildings.
In the presence of organic matter their activity will be reduced therefore applied to the skin are worse accepted.
What are some miscellaneous compounds?
Biguanidine (Chlorhexidine)
Heavy metal salts (Ag,Cu)
Chlorhexidine use and mechanism of action
- has a potent antiseptic activity against both Gr+ and Gr- organisms but not against spores = USED IN SURGERY
Because of its antiseptic properties and low potential for systemic or dermal toxicity, chlorhexidine has been incorporated into shampoos, ointments, skin and wound cleansers, teat dips, and surgical scrubs.
In susceptible organisms, chlorhexidine disrupts the cytoplasmic membrane.
Heavy metal salts mechanism of action
The toxic salts of heavy metals react with bacterial enzymes to form
a complex. This process is known as an oligodynamic effect and is detrimental to the bacterial cell. They have mainly bacteriostatic, in higher conc. also bactericidal action.
Describe the effect of silver compounds
Silver compounds can have caustic, adstringent, and antibacterial effects. Silver ions combine with sulfhydryl, amino, phosphate, and carboxyl groups, and thus precipitate proteins, in addition to interfering with essential metabolic activities of microbial cells.
Use of inorganic silver salts and organic silver preparations
Inorganic silver salts- sometimes applied as a dressing on burns
Organic silver preparations (colloidal silver) are bacteriostatic and have a more sustained effect. They do not irritate the tissues and have little astringent or caustic effect because they don’t ionize and release many free silver ions that would cause these effects. Used in antiseptic eye solutions
Use of copper salts
Copper sulphate has germicidal, fungicidal and astringent activities. In vet. med. has been as an antiseptic for hooves in sheep (dipping) to treat pododermatitis.
