Chemical sterilizationAntiseptics and disinfectantsLaila mahmoudM.Pharm (clinical Pharmacy)(clinical pharmacy, Ph.D)

Learning Objectives To be able to define antiseptic and disinfectant To know the characteristics of ideal disinfectantTo understand the mechanism of action of disinfectantTo be able to recognize antiseptics groups with conc used and bacterial spectrumTo be able to recognize disinfectant groups with conc used and bacterial spectrum

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Disinfection

Disinfectants are bacteriocidal chemical solutions used to clean inanimate objects

Antiseptics are bacteriostatics chemicals formulated for application to living tissue

Disinfection Action depend on Chemical propertiesConcentrationDuration Sensitivity of microbialsKind of microbials: Bacteria (G+/G-),ViralEnvironment: pH, Temp, matter

Ideal disinfectantsDestroy all kind of microbialRapidly actionLong duration of action High stability Less or nontoxic and adverse effectCheap and easy to use colorless, odorless

Disinfectant (Mode of action)Denature protein and lipid:Release chemical bond: Aldehydes-EnzymesIncrease positive ion (Oxidant): Halogens, H2O2, Ozone

Antiseptic agentsAlcohols Chlorhexidine Oxidizing agentsIodine, IodophorsPeroxides - Hydrogen peroxide Potassium permanganate Heavy Metals :Mercuric bichloride Surfaceactive compounds : Soaps

Disinfectant agentsPhenols and Related CompoundsOxidizing agents :Chlorine Reducing agents: AldehydesSurface-active compounds :QACsGaseous Disinfectants

Antiseptic agents1. Alcohol Kill bacteria, fungi, but not endospores or naked viruses.Lipid soluble lipoprotein cell membrane denature cell membrane precipitate protein

Used to mechanically wipe microbes off skin before injections or blood drawing.

Ethanol: Optimum concentration is 70%. Isopropanol: 50% Rubbing alcohol. Better disinfectant than ethanol. Also cheaper and less volatile.

Disadvantages:Not good for open wounds, because cause proteins to coagulate.Not recommend for high level disinfectant -blood protein denature and adhere to instrument -prolong use: damage lenses, rubber, plastic instrumentsRapid evaporation Limit contact timeAntiseptic agents1. Alcohol

Antiseptic agents1. Alcohol Advantages:The largest reduction in bacterial count (1-3 min, kill 80% of bact.)The safest antiseptic

Adverse effects: drying skinNot for fresh or open wound (irritate) local irritationdamaging corneal tissue

Antiseptic agents2. Chlorexidine Rapidly actionDisrupt the cell membrane and precipitate cell contentBetter against vegetative bacteria gram + than gram Less effective for fungiNon effect on virusesNo action on sporesChx formulation 4% conc. (most effective) Retained action in organic matter

Antiseptic agents3. Oxidizing agentsBactericidal, short action

Hydrogen peroxidePotassium permanganateHalogen

A. Hydrogen peroxide3-90 % H2O2 in water (Most use 3%)Short acting agentBactericidal agent (Gr+/-)Active against Lipophillic virus (related catalase and peroxidase enzymes)Sporicidal at higher temperatures.Act as an oxidant by producing hydroxyl free radicals(*OH) attack essential cell components (lipids, proteins, and DNA)

A. Hydrogen peroxideNot good for open wounds because quickly broken down by catalase present in human cells. Effective in disinfection of inanimate objects.

Indication:Used as an antiseptic: cleaning contaminated woundUsed by food industry Used in the disinfection of soft contact lenses

B. Potassium permanganate Antiseptic and disinfectant agentsBroad antimicrobial agentsTurn brown colourInactivatedIntense purple color in solution: stains tissues and clothing brownEffective algicide (0.01%) and virucide (1%)Conc 1: 10,000 BactericidalUsed for wound

C. IodineRapidly bactericidal(Gr+/-)Fungicidal, tuberculocidal, virucidal and sporicidal (Lipophillic)Interfere metabolic reaction, disrupt protein and nucleic acid structure & synthesisTincture of iodine:1-2 % iodine solution in 70% ethyl alcohol. Stains skin and clothes, somewhat irritatingLogols solution: Aqueous iodine solution 5% Churchills iodine (6.5% Alcohol.)

Side effect: Irritating & allergenic skin, corrssive, delay healing Active greater than alcohol Indication: antiseptic and disinfectantC. Iodine

Antiseptic agents4. Heavy metalInclude copper, selenium, mercury, silver, and zinc. Oligodynamic action: Very tiny amounts are effective.Act as Bacteriostatic by:Inhibit metabolism and precipitate proteinInhibit enzyme action of bacteria and tissues

A. Silver: 1% silver nitrate used to protect infants against gonorrheal eye infections until recently.B. Mercury Organic mercury compounds like merthiolate and mercurochrome are used to disinfect skin wounds.C. Copper Copper sulfate is used to kill algae in pools and fish tanks.D. Selenium Kills fungi and their spores. Used for fungal infections. Also used in dandruff shampoos.E. Zinc Zinc chloride is used in mouthwashes. Zinc oxide is used as antifungal agent in paints.

Heavy Metals

Antiseptic agents5. Surfaceactive compounds SoapsAnionic surface-active agentsSodium, Potassium salts of fatty acidMost soaps dissolve in water (pH 7.0-10.0)Remove dirt from skin surfaces (surface secretion, desquamated epithelium, bacteria)

Types of Disinfectants1. Oxidizing agent:

Halogens: Effective alone or in compounds.Chlorine: When mixed in water forms hypochlorous acid:Cl2 + H2O ------>H+ + Cl-+ HOCl Hypochlorous acid Used to disinfect drinking water, pools, and sewage. Chlorine is easily inactivated by organic materials.

Types of Disinfectants1. Oxidizing agent:

Chlorine: Action inhibition of cellular enzymatic reaction, protein deneturation, inactivation of nucleic acidsDisadvantages :Corrosively metal, destroy fabric, strongly odorSanitize dairy equipment, hospital floors, animal, housing quarters

Types of Disinfectants2. Aldehydes: Inactivate proteins by forming covalent crosslinks with several functional groups.A. Formaldehyde gas: Excellent disinfectant. Commonly used as formalin, a 37% aqueous solution. Formalin was used extensively to preserve biological specimens and inactivate viruses and bacteria in vaccines. Irritates mucous membranes, strong odor.Bactericidal both Gr+ and and TBVirucidal

Types of Disinfectants2. Aldehydes:

B. Glutaraldehyde: Less irritating and more effective than formaldehyde.sterilizing agent Commonly used to disinfect hospital instruments A 2% solution of glutaraldehyde (Cidex) is: Bactericidal, tuberculocidal, and viricidal in 10 minutes. Sporicidal in 3 to 10 hours.Less adverse effectNon corrossive InstrumentsStable in acid

Types of Disinfictants3. Surface-active compoundsQACs (Quaternary Ammonium Compounds: benzalkonium chlorideBacteriostatic or cidal action (depend on conc)Good efficacy in basic conditionDenature proteinActive bact. Gr+ than Gr-Inactivated in organic debris, hard water, anionic soap.Fungistatic,Inactivate virusesSanitation of non-critical surfaces

Types of Disinfectants4. Gaseous Sterilizers: Chemicals that sterilize in a chamber similar to an autoclave.Denature proteins, by replacing functional groups with alkyl groups.Ethylene Oxide:Kills all microbes and endospores, but requires exposure of 4 to 18 hours. Toxic and explosive in pure form. Highly penetrating. Most hospitals have ethylene oxide chambers to sterilize mattresses and large equipment.

Phenol (carbolic acid) was first used by Lister as a disinfectant.Rarely used today because it is a skin irritant and has strong odor.Used in some throat sprays and lozenges. Acts as local anesthetic. Destroy plasma membranes and denature proteins. Advantages: Stable, persist for long times after applied, and remain active in the presence of organic compounds.Types of Disinfectants5. Phenol and related compounds

5. Phenol and related compoundsBacteriostatic (conc.0.1-1 %)Bactericidal, fungicidal, virucidal (conc. 1-2%)Conc 5 % : Kill anthrax spores 48 hr (strongly irritating, corrosively tissues) Oral :CNS effects and Cardiovascular effectsMain usage : disinfection of equipment

Phenolics are chemical derivatives of phenol1. Cresol (cresylic acid):Bactericidal agent less toxicCommonly used disinfectant (inanimate objects)Sporicidal Anthraxs spore 2 % Cresol (Lysol)2. Chloroxylenols (Detol): Broad-spectrum bactericidal agentactivity against gram + > -PCMX and DCMX5. Phenol and related compounds

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