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SterilizationSterilization

Presented By

GajeshSanjith k

Rajesh Raika

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D efinitions :

Sterilization: Killing or removing all formsof microbial life (including endospores) in a

material or an object. Heating is the most commonly used

method of sterilization.

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D efinitions :

Sepsis: Indicates bacterial contamination.

Asepsis: Absence of significant contamination.

Aseptic techniques : are used to preventcontamination of

Surgical instruments

Medical personnel Food industry.

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D efinitions :

Bacteriostatic Agent: An agent thatinhibits the growth of bacteria, but does notnecessarily kill them.

Germicide: An agent that kills certainmicroorganisms.

x Bactericide: An agent that kills bacteria. Mostdo not kill endospores.

x Viricide: An agent that inactivates viruses.x Fungicide: An agent that kills fungi.x Sporicide: An agent that kills bacterial

endospores of fungal spores.x

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Sterilizing Agents

Type of agents 1. Physical

Heat : Moist heat

Dry heat Filtration Radiation

2. Chemical

Most clinics use physical agents

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Physical Methods of MicrobialControl:

Moist Heat: Kills microorganisms bycoagulating their proteins.

In general, moist heat is much more effectivethan dry heat.

1. Boiling: Heat to 100oC or more at sea level. Killsvegetative forms of bacterial pathogens, almost all viruses,and fungi and their spores within 10 minutes or less.

Endosporesand some viruses are not destroyed thisquickly. However brief boiling will kill most pathogens.

x Hepatitis virus: Can survive up to 30 minutes of boiling.

x Endospores: Can survive up to 20 hours or more of boiling.

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Sterilizes :InstrumentsSyringes

NeedlesOther materials

2: Autoclave: Chamber which is filled with hotsteam under pressure. Preferred method of

sterilization, unless material is damaged by

heat, moisture, or high pressure..x

Closed Chamber with High Temperature andPressure

xTemperature of steam reaches 121oC at twice

atmospheric pressure.All organisms and endospores are killed within 15

minutes.

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3 : Pasteurization:Developed by Louis Pasteur to preventthe spoilage of beverages. Used to reduce microbes

responsible for spoilage of beer, milk, wine etc.

x Classic Method of Pasteurization: Milk was exposed to

65oC for 30 minutes.

x High Temperature Short Time Pasteurization

(HTST):Used today. Milk is exposed to 72oC for 15

seconds.

x Ultra High Temperature Pasteurization (UHT): Milk is

treated at 140o

C for 3 seconds and then cooled veryquickly in a vacuum chamber.

x Advantage: Milk can be stored at room temperature for

several months.

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Dry Heat: Kills by oxidation effects.

x Direct Flaming: Used to sterilize inoculating loops and

needles.

x Hot Air Oven : Require 2 hours at 170oC for

sterilization. Dry heat is transfers heat less effectively

to a cool body, than moist heat.

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Filtration

Remove microorganism physically.

Complete removal of microorganisms andparticles of a certain size from liquid orgas

Used by vet personnel in producing sterile

and particle-free fluids, such asintravenous fluids.

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Seitz filter-asbestos compressed into filterpad.

berkefeld filter-made of diatomaceous earth.

Chamberland-Pasteur filter-unglazedporcelain.

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Physical Methods of MicrobialControl: Radiation: energy transmitted through variety of forms.

Three types of radiation kill microbes 1. Ionizing Radiation: Gamma rays, X rays, electron

beams, or higher energy rays. Have short wavelengths (less than 1 nanometer).

Cause mutations in DNA and produce peroxides. Used to sterilize pharmaceuticals and disposable medical

supplies. Food industry is interested in using ionizing radiation.

Disadvantages: Penetrates human tissues. May causegenetic mutations in humans.

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Forms of Radiation

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Physical Methods of MicrobialControl:

2. Ultraviolet light (NonionizingRadiation): Wavelength is longer than 1nanometer. Damages DNA by producingthymine dimers, which cause mutations.

Used to disinfect operating rooms, nurseries,cafeterias.

Disadvantages: Damages skin, eyes.Doesnt penetrate paper, glass, and cloth.

x

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Physical Methods of MicrobialControl:

3.Microwave Radiation: Wavelength rangesfrom 1 millimeter to 1 meter.

Heat is absorbed by water molecules. May kill vegetative cells in moist foods. Bacterial endospores, which do not contain

water, are not damaged by microwave radiation. Solid foods are unevenly penetrated by

microwaves.

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Chemical Methods of Microbial ControlTypes of Disinfectants

1. Phenols and Phenolics:x

xPhenol (carbolic acid) was first used by Lister asa disinfectant.

x Rarely used today because it is a skin irritant and hasstrong odor.

x Used in some throat sprays and lozenges.x Acts as local anesthetic.

x

x Destroy plasma membranes and denature

proteins.x Advantages: Stable, persist for long times

after applied, and remain active in thepresence of organic compounds.

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2. Halogens: Effective alone or in compounds.

A. Iodine:x Tincture of iodine (alcohol solution) was one of first

antiseptics used.x Stains skin and clothes, somewhat irritating.x

x Iodophors: Compounds with iodine that are slowreleasing, take several minutes to act. Used as skiantiseptic in surgery. Not effective against bacterialendospores.x

x Betadinex Isodine

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Iod

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&

Iod

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http://www.encolombia.com/salud/primerosauxilios2.htmhttp://www.venousaccess.com/Central%20line%20after%20care.htmhttp://www.waynesbottleworld.com/poisons.htm

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2. Halogens: Effective alone or in compounds.

B. Chlorine:x When mixed in water forms hypochlorousacid:

Cl2 + H2O ------> H+ + Cl- + HOCl

Hypochlorous acid

x Used to disinfect drinking water, pools, and sewage.x

x Chloramines: Consist of chlorine and ammonia. Lesseffective as germicides.

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3. Alcohols:x Kill bacteria, fungi, but not endospores or naked

viruses.

x Act by denaturing proteins and disrupting cellmembranes.

x Evaporate, leaving no residue.x Used to mechanically wipe microbes off skin before

injections or blood drawing.x Not good for open wounds, because cause proteins to

coagulate.x

x

x

x Ethanol: Drinking alcohol. Optimum concentration is

70%.

x Isopropanol: Rubbing alcohol. Better disinfectant than

ethanol. Also cheaper and less volatile.

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4. Heavy Metals:x Include copper, selenium, mercury, silver, and zinc.x Oligodynamic action: Very tiny amounts are effective.

A. Silver:x 1% silver nitrate used to protect infants against

gonorrheal eye infections until recently.(sexuallytransmitted infections .Neisseria gonorrheae is one of the few bacteria capableof penetrating the protective layers of the eye, causing inner-eye infection.)

B. Mercuryx 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.

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4. Heavy Metals:D. Selenium

x Kills fungi and their spores. Used for fungal infections.

x Also used in dandruff shampoos.

E. Zinc

x Zinc chloride is used in mouthwashes.

x Zinc oxide is used as antifungal agent in paints.

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5. Quaternary Ammonium Compounds (Quats):x Widely used surface active agents.x Cationic (positively charge) detergents.x

Effective against gram positive bacteria, less effectiveagainst gram-negative bacteria.x Also destroy fungi, amoebas, and enveloped viruses.x

Advantages: Strong antimicrobial action, colorless, odorless, tasteless, stable, and nontoxic.

Diasadvantages: Form foam. Organic matter interferes with effectiveness. Neutralized by soaps and anionic detergents.

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6. Aldehydes:x Inactivate proteins by forming covalent crosslinks with

several functional groups.

A. Formaldehyde gas:x Excellent disinfectant.x Commonly used as formalin, a 37% aqueous solution.x Formalin was used extensively to preserve biological

specimens and inactivate viruses and bacteria invaccines.

x Irritates mucous membranes, strong odor.x Also used in mortuaries for embalming.

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7. Gaseous Sterilizers:x Chemicals that sterilize in a chamber similar to an

autoclave.

x Denature proteins, by replacing functional groups withalkyl groups.

A. Ethylene Oxide:

x Kills all microbes and endospores, but requiresexposure of 4 to 18 hours.

x Toxic and explosive in pure form.

x Highly penetrating.

x Most hospitals have ethylene oxide chambers tosterilize mattresses and large equipment.

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8. Peroxygens (Oxidizing Agents):x Oxidize cellular components of treated microbes.

x Disrupt membranes and proteins.

A. Ozone:

x Used along with chlorine to disinfect water.

x Helps neutralize unpleasant tastes and odors.

x More effective killing agent than chlorine, but less stableand more expensive.

x Highly reactive form of oxygen.

x Made by exposing oxygen to electricity or UV light.

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8. Peroxygens (Oxidizing Agents):

B. Hydrogen Peroxide:

x Used as an antiseptic.

x Not good for open wounds because quickly brokendown by catalase present in human cells.

x Effective in disinfection of inanimate objects.

x Sporicidal at higher temperatures.

x Used by food industry and to disinfect contact lenses.

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8. Peroxygens (Oxidizing Agents):C. Benzoyl Peroxide:

x Used in acne medications.

D. Peracetic Acid:

x One of the most effective liquid sporicides available.

x

x Sterilant :x Kills bacteria and fungi in less than 5 minutes.

x Kills endospores and viruses within 30 minutes.

x

x Used widely in disinfection of food and medicalinstruments because it does not leave toxic residues.x

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Chemical Antimicrobials

* Type of Disinfectant: H = High level; I = Intermediate level; L = Low level

http://www.safety.queensu.ca/biocom/disin.htm

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