ANTISEPTICS AND DISINFECTANTS

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Antiseptics

• Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infections, sepsis or putrefaction
• Antiseptics are used on living tissues
• Disinfectants are used on non-living items, to protect the spreading of germs and infection to humans and animals.

• Disinfectants usually come in liquid form or in spray.
• Antiseptics can come in form of ointments.
• Antibiotics differ from antiseptics and disinfectants by their ability to be transported through the lymphatic system to destroy bacteria within the body.

FACTS TO KNOW

• Some antiseptics are true germicides
• They can be bactericidal or bacteriostatic
• Antibacterials include antiseptics that have proven ability to act against bacteria.
• Microbicides which destroy virus particles are called viricides or antivirals.
• Antifungals also known as antimycotics are pharmaceutical fungicides used to treat and prevent mycosis.

TYPES OF DISINFECTANTS

• Phenolic compds, Halogens, Alcohols, Aldehydes, Gases, Surface active agents, Oxidizing agents, Dyes, Heavy metals, Acids and alkalis.

PHENOLIC COMPDS.

• Most widely used antiseptics and disinfectants in labs and hospitals
• Bactericidal and bacteriostatic and some are fungicidal.

• They act by denaturing proteins and disrupting cell membranes of microbes.

Phenol

• It is active against vegetative forms of bacteria, Mycobacterium tuberculosis and fungi.
• Excellent disinfectant for feces, blood, pus sputum, etc.
• It is not suitable for application to skin or mucous membrane.

Cresol

• Cresols are more germicidal and less poisonous than phenol but corrosive to living tissues.
• They are used for cleaning floors (1% soln), for disinfection of surgical instruments and for disinfection of contaminated objects
• Lysol is a solution of cresols in soap.

Halogenated diphenyl compds

• Hexachlorophene
• Chlorhexidine
• They are highly effective against both gram-positive and gram-negative bacteria.
• They are used as skin antiseptics and for the cleaning of wound surfaces.

NOTE

• Hexachlorophene has been one of the most popular antiseptics because once applied it persists on the skin and reduces growth of skin bacteria for longer periods.
• It can cause brain damage and is now used in hospital nurseries only after a staphylococcal outbreak.

Halogens

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Halogens

• Halogens include fluorine, bromine, chlorine and iodine.
• A group of nonmetallic elements that occur in minerals, sea water and salts.
• Occur in the ionic (halide) or nonionic state
• Most halogens exert their antimicrobial activity primarily in their nonionic state but not in the halide state e.g chloride, iodide.

• These agents are highly effective disinfectants and antiseptics
• They are microbiocidal and not just microbiostatic
• They are also sporicidal with longer exposure.
• Chlorine and Iodine are the only two routinely used halogens because fluorine and bromine are dangerous to handle.

Chlorine and its compds.

• Chlorine is used for disinfection and antisepsis.
• Liquid chlorine and gaseous chlorine
• Hypochlorites
• In soln the compds combine with water and release hypochlorous acid which leads to the denaturation of enzymes in microbes.

• Gaseous and liquid chlorine are used for large-scale disnfection of drinking water, sewage waste water from sources such as agriculture and industry.
• Chlorination at a concentration of 0.6 – 1.0 part of chlorine per million parts of water makes water potable and safe to use.
• 5% of sodium hypochlorite(bleach) is used as a disinfectant , deodorizer and stain remover.

Iodine and its comps.

• It kills all types of microorganisms.
• It rapidly penetrates the cells of microbes.
• Free iodine in soln
• Aqueous iodine contains 2% free iodine and 2.4% sodium chloride.
• It is used as topical antiseptic before surgery and also as a treatment for burnt and infected skin.

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• 5% iodine and 10% potassum iodide is used primarily as a disinfectant for plastic items, rubber instruments, cutting blades and thermometers.
• Iodine tincture is 2% soln of iodine and sodium iodide in 70% alcohol used in skin antisepsis.
• Iodine tablets are used for disinfecting water during emergencies or for destroying pathogens in impure water supplies.

Iodophores or Iodophore compds.

• These are complexes of iodine and a neutral polymer such as polyvinyl alcohol.
• This formulation permits the slow release of free iodine and increases its degree of penetration.
• These compds have largely replaced free iodine solns in medical antisepsis because they are less prone to staining or irritating tissues.

• Betadine, Povidone and Isodine
• These are the common iodophor compds that contain 2-10% of available iodine.
• They are used to prepare skin and mucuos membranes for surgery and in surgical hand scrubs.
• They are also used to treat burns and to disinfect equipments.

• Betadine is an effective means of preventing eye infections in new born infants and it may replace antibiotics and silver nitrate as method of choice.

ALCOHOLS

• Alcohols are among the most widely used disinfectants and antiseptics.
• They are bactericidal and fungicidal but not sporicidal and viricidal.

• Ethyl alcohol
• Isopropyl alcohol at 60-70% conc
• The two most popular alcohol germicides
• Used as skin antiseptics
• Act by denaturing bacterial proteins and by dissolving membrane lipids.
• Isopropyl alcohol is used for disinfection of clinical thermometers
• Methyl alcohol effective against fungal spores.

Aldehydes

• Formaldehyde
• Glutaraldehyde
• Used as disinfectants
• They are sporicidal and sterilants.
• Formaldehyde is usually dissolved in water or alcohol before use.
• In aqueous soln it is bactericidal, sporicidal and viricidal.

• Formalin soln is 40% aldehyde in aqueous soln.
• Formalin is used to
• Preserve fresh tissue specimens
• Destroy anthrax spores in hair and wool
• Prepare toxoids from toxins
• Sterilize bacterial vaccines
• Kill bacterial cultures and suspensions.

• Glutaraldehyde --- a 2% buffered soln is an effective disinfectant.
• It is less irritating than formaldehyde
• It is used to disinfect hospital and laboratory equipments.
• Disinfects objects within 10 minutes but may require as long as 12 hours to destroy all spores
• Effective against tubercle bacilli, fungi and viruses.

• Used to clean cystoscopes, bronchoscopes, corrugated rubber anesthetic tubes, face masks, plastic endotracheal tubes, metal instruments and polythene tubing.

Gases

• Various gaseous agents are used for sterilization of large volume of heat sensitive disposable items and also instruments.

• Ethylene oxide liquid
• Formaldehyde gas
• Betapropiolactone gas.

Ethylene oxide

• This is a colorless liquid used for gaseous sterilization.
• It is active against all kinds of bacteria, spores and viruses.

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• It is used to sterilize disposable plastic petri dishes, sutures, syringes, heart-lung machines, respirators and dental equipments.
• It is highly inflammable and carcinogenic.
• Extensive aeration of the sterilized materials is necessary to remove residual ethylene oxide gas, which is toxic.

Formalin gas

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• Used for the fumigation of operation theaters, wards, sick rooms and laboratories
• Sterilization of instruments and heat-sensitive catheters, clothing and bedding, furniture and books.
• The gas is toxic when inhaled and is irritant to eye, hence its effect is nullified by exposure to ammonia.
• Inflammable and carcinogenic.

Surface active agents.

• Substances that alter energy relationship at interfaces producing a reduction in surface tension.
• Detergents
• Due to their amphipathic nature, detergents solubilize and are very effective cleansing agents.

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Surface active agents are of 4 types

• Cationic surface active agents(detergents)
• Effective disinfectants
• Benzalkonium chloride
• Cetylpyridinium chloride
• Kill most bacteria but not M. tuberculosis, endospores or viruses.
• They are inactivated by hard water and soap.

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• They are often used as skin antiseptics and also as disinfectants for utensils and small instruments.
• Quaternary ammonium compds e.g
• Cetrimide
• The most popular cationic detergents.

Anionic surface active agents :

• These are soaps prepared from saturated or unsaturated fatty acids which act better acidic PH.

• The soaps prepared from saturated fatty acids are effective against gram negative organisms whereas those prepared from unsaturated fatty acids are more active against gram positive bacilli and Neisseria.

Nonionic surface active agents:

• They are non toxic and some of them may even promote the growth of bacteria

Amphoteric or ampholytic compds:

• These are active against a wide range of gram positive and gram negative bacteria and a few viruses. They are called Tego compds.

Oxidizing agents includes :

• Halogens
• Hydrogen Peroxide
• Potassium Permanganate
• Sodium Perborate

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• They are good disinfectants and antiseptics but are less effective in the presence of organic matter.
• Hydrogen Peroxide used as 3% soln is a weak disinfectant.
• Useful for cleaning of wounds and for mouth wash or gargle.
• Potassium Permanganate is bactericidal and active against viruses.

Dyes

• Dyes that have been used extensively as skin and wound antiseptics are :
• Acridine dyes
• Aniline dyes.

Acridine dyes include :

• Acriflavine
• Euflavine
• Proflavine

• Andaminacrine
• They show more activity against gram-positive bacteria than against gram-negative organisms.
• The yellow acridine dyes, acriflavine and proflavine are sometimes used for antisepsis and wound treatment in medical and veterinary clinics.

Aniline dyes

• Gentian violet
• Crystal violet
• Malachite violet
• Are more active against gram-positive bacteria than gram-negative organisms.
• Active against fungi hence incorporated into solutions and ointments to treat fungal skin infections such as ringworm.

• Dyes have limited applications because they stain and have a narrow spectrum of antimicrobial activity.

Heavy metals

• Soluble salts of:
• Mercury, silver, copper, arsenic, etc
• Bactericidal and bacteriostatic activity.
• They precipitate cell proteins.

• Silver compds are widely used as antiseptics.
• Silver sulfadiazine is used for burns.
• Silver nitrate is used as a prophylactic agent in ophthalmia neonatorum in newborn infants.
• Copper sulfate is an effective algicide in lakes and swimming pools.

Acids and alkalis

• Acids e.g sulfuric acid, nitric acid, hydrochloric acid and benzoic acid

• Alkalis e.g. potassium hydroxide and ammonium hydroxide and sodium hydroxide etc
• Germicidal in nature.
• They kill microorganisms by hydrolysis and altering the pH of the medium
• They are rarely used as disinfectants.

Organic acids

• Organic acids are widely used in food preservation
• because they prevent spore germination and bacterial and fungal growth
• because they are generally regarded as safe to eat.
• Acetic acid in the form of vinegar is a pickling agent that inhibits bacterial growth.
• Propionic acid is added into breads and cakes to retard molds,

• Lactic acid are added into olives to prevent of anaerobic bacteria, especially the clostridia
• Benzoic acid and sorbic acids
• Added to beverages, syrups and margarine to inhibit yeasts.