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Sterilization & Disinfection FOUNDATION BLOCK. Definitions Sterilization: complete killing of all...

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Sterilization & Sterilization & Disinfection Disinfection FOUNDATION BLOCK FOUNDATION BLOCK
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Sterilization & Sterilization & DisinfectionDisinfection

FOUNDATION BLOCKFOUNDATION BLOCK

DefinitionsDefinitions

Sterilization: Sterilization: complete killing of all complete killing of all forms of microorganisms.forms of microorganisms. including including bacterial sporesbacterial spores

DisinfectionDisinfection: killing or removing of : killing or removing of harmful vegetative microorganisms.harmful vegetative microorganisms.

DisinfectantDisinfectant: chemical substance : chemical substance used to achieve disinfection. used to achieve disinfection. Antiseptic: disinfectant that can be Antiseptic: disinfectant that can be safely used on living tissues.safely used on living tissues.

Methods of sterilization:Methods of sterilization:

A.A. Physical methods:Physical methods:

B.B. Chemical Methods: Chemical Methods:

PHYSICAL METHODSPHYSICAL METHODS

HEAT HEAT : Most important should : Most important should be used whenever possiblebe used whenever possible could be ;could be ;

AA-Dry heat -Dry heat at temperature of at temperature of 160˚c for one hour.160˚c for one hour.

BB- Moist heat - Moist heat eg in the eg in the autoclave autoclave

At 121 or 134 for 15 or 1 minute At 121 or 134 for 15 or 1 minute

RadiationRadiation

U.V. light U.V. light – Has limited sterilizing power because of Has limited sterilizing power because of

poor penetration into most materials. poor penetration into most materials. Generally used in irritation of air in certain Generally used in irritation of air in certain areas eg. Operating rooms and areas eg. Operating rooms and T.BT.B. labs.. labs.

Ionizing radiation- Ionizing radiation- – e.g. e.g. Gamma radiationGamma radiation: Source Cobalt60 has : Source Cobalt60 has

greater energy than U.V. light, therefore greater energy than U.V. light, therefore more effective. Used mainly in industrial more effective. Used mainly in industrial facilities e.g. sterilization of disposable facilities e.g. sterilization of disposable plastic syringes, gloves, specimens plastic syringes, gloves, specimens containers and Petri dishes.containers and Petri dishes.

FiltrationFiltration

May be done under either negative or May be done under either negative or positive pressure. Best known example positive pressure. Best known example is the membrane filter made from is the membrane filter made from cellulose acetate. Generally removes cellulose acetate. Generally removes most bacteria but viruses and some most bacteria but viruses and some small bacteria e.g. small bacteria e.g. ChlamydiasChlamydias & & MycoplasmasMycoplasmas may pass through. Thus may pass through. Thus filtration does not technically sterilize filtration does not technically sterilize items but it adequate for circumstances items but it adequate for circumstances under which is used.under which is used.

Main use: for heat labile substances e.g. Main use: for heat labile substances e.g. sera, antibiotics.sera, antibiotics.

Chemical MethodsChemical Methods

Some chemical substances Some chemical substances may be used to achieve may be used to achieve sterilization e.g. sterilization e.g. Gluteraldehyde and Ethylene Gluteraldehyde and Ethylene oxide.oxide.

Sterilization by HeatSterilization by HeatMost common methodMost common method Dry HeatDry Heat

Dry Heat- kills microorganisms by Dry Heat- kills microorganisms by destroying their oxidative processes.destroying their oxidative processes.– Simplest method is exposing item to be sterilized Simplest method is exposing item to be sterilized

to the naked flame e.g. Bunsen burner- for to the naked flame e.g. Bunsen burner- for sterilizing bacteriological loops, knives, blades.sterilizing bacteriological loops, knives, blades.

– Hot air oven Hot air oven expose items to 160 °C for 1 hour.expose items to 160 °C for 1 hour. Has electric element in chamber as source Has electric element in chamber as source

of heat plus a fan to circulate air for even of heat plus a fan to circulate air for even distribution of heat in chamber. Oven distribution of heat in chamber. Oven without fan is dangerous. Used for: without fan is dangerous. Used for:

metalsmetals GlasswareGlassware Ointment/ oils/ waxes/powderOintment/ oils/ waxes/powderi.e. items that are lacking wateri.e. items that are lacking water

HOT AIR OVENHOT AIR OVEN

Moist HeatMoist Heat

Uses hot waterUses hot water. Moist heat kills . Moist heat kills microorganisms by microorganisms by denaturating proteins.denaturating proteins.

Autoclaving Autoclaving –– standard sterilization standard sterilization method in hospitals.method in hospitals.

The equipment is called The equipment is called AutoclaveAutoclave and it and it works under the same principle as the works under the same principle as the pressure cooker where water boils at pressure cooker where water boils at increased atmosphere pressure i.e. increased atmosphere pressure i.e. because of increase pressure the boiling because of increase pressure the boiling point of water is point of water is >100 °C. >100 °C.

The autoclave is a tough double walled The autoclave is a tough double walled chamber in which air is replaced by pure chamber in which air is replaced by pure saturated steam under pressure.saturated steam under pressure.

Advantages of AutoclaveAdvantages of Autoclave

1. T °> 100 therefore 1. T °> 100 therefore spores killedspores killed.. 2. Condensation of steam generates 2. Condensation of steam generates

extra heat.extra heat. 3. The condensation also allows the 3. The condensation also allows the

steam to penetrate rapidly into porous steam to penetrate rapidly into porous materials.materials.

Note: that autoclavable items must be Note: that autoclavable items must be steam permeable. Can not be used for steam permeable. Can not be used for items that are lacking wateritems that are lacking water..

The The airair in the chamber is evacuated and in the chamber is evacuated and filled with saturated steam. The chamber is filled with saturated steam. The chamber is closed tightly the steam keeps on filling into closed tightly the steam keeps on filling into it and the pressure gradually increases. The it and the pressure gradually increases. The items to be sterilized get completely items to be sterilized get completely surrounded by saturated steam (moist heat) surrounded by saturated steam (moist heat) which on contact with the surface of material which on contact with the surface of material to be sterilized condenses to release its to be sterilized condenses to release its latent heat of condensation which adds to latent heat of condensation which adds to already raised temperature of steam so that already raised temperature of steam so that eventually all the microorganisms in what eventually all the microorganisms in what ever form ever form ––are killed.are killed.

The usual temperature achieved is 121 °C at a The usual temperature achieved is 121 °C at a pressure of 15 pps.i. at exposure time of only 15 minspressure of 15 pps.i. at exposure time of only 15 mins

Monitoring of AutoclavesMonitoring of Autoclaves

1. 1. PhysicalPhysical- use of thermocouple to - use of thermocouple to measure accurately the temperature.measure accurately the temperature.

2. Chemical- it consists of heat 2. Chemical- it consists of heat sensitive chemical that changes sensitive chemical that changes colour at the right temperature and colour at the right temperature and exposure time. exposure time.

e.ge.g. a)- Autoclave tape. a)- Autoclave tape b)- Browneb)- Browne’’s tube.s tube. 3. 3. BiologicalBiological –– where a spore-bearing where a spore-bearing

organism is added during the organism is added during the sterilization process and then cultured sterilization process and then cultured later to ensure that it has been killed.later to ensure that it has been killed.

Moist heat: Other Moist heat: Other ApplicationsApplicationsPasteurization Pasteurization Used heat at temperatures sufficient Used heat at temperatures sufficient

to inactivate harmful organism in to inactivate harmful organism in milk. The temperatures sterilization milk. The temperatures sterilization a not achieved . a not achieved .

Temperature may be 74°C, for Temperature may be 74°C, for 3-5 secs ( 3-5 secs ( Flash methodsFlash methods or 62°C for or 62°C for 30 mins. ( 30 mins. ( Conventional method Conventional method ).).

b)- b)- Boiling Boiling –– quite common quite common especially in domestic circumstances.especially in domestic circumstances.

Methods of Methods of pasteurizationpasteurization Temp= 63-66 C for 30 minutes Temp= 63-66 C for 30 minutes

((conventional method conventional method )) Temp=72-73 C for 3-5 Temp=72-73 C for 3-5

seconds( seconds( flash method )flash method )

PASTEURIZATIONPASTEURIZATION

Pasteurization of milkPasteurization of milk

To prevent diseases like :To prevent diseases like : Typhoid feverTyphoid fever BrucellosisBrucellosis TuberculosisTuberculosis Q feverQ fever

II II Sterilization by Sterilization by Chemical MethodsChemical MethodsUseful for heat sensitive materials e.g. plastics and lensed Useful for heat sensitive materials e.g. plastics and lensed

instruments endoscopes).instruments endoscopes).1. 1. Ethylene Oxide ChamberEthylene Oxide Chamber Ethylene oxide alkylates DNA molescules and thereby Ethylene oxide alkylates DNA molescules and thereby inactivates microorganisms.inactivates microorganisms. Ethylenes oxide may cause explosion if used pure so it is Ethylenes oxide may cause explosion if used pure so it is

mixed with an inert gas e.g Neon, Feron at a ratio of mixed with an inert gas e.g Neon, Feron at a ratio of

10:90 10:90 Requires high humidity and used at relative humidity Requires high humidity and used at relative humidity 50-60% Temperature : 55-60°C and exposure period 4-6 50-60% Temperature : 55-60°C and exposure period 4-6

hours.hours.2. 2. Activated alkaline Gluteraldehyde 2%Activated alkaline Gluteraldehyde 2% Immerse item in solution for about 20 mins. If organism is Immerse item in solution for about 20 mins. If organism is

T.B. T.B. But if spores then immersion period 2-3 hours.But if spores then immersion period 2-3 hours.

ETHYLENE OXIDE ETHYLENE OXIDE CHAMBERCHAMBER

Factors influencing Factors influencing activity of disinfectantsactivity of disinfectants 1. Activity directly 1. Activity directly

proportional to proportional to temperature.temperature. 2. Directly proportional to 2. Directly proportional to

concentrationconcentration up to a point up to a point –– optimum concentration. After optimum concentration. After this level no advantage in this level no advantage in further increases in further increases in concentration.concentration.

Factors influencing Factors influencing activity of disinfectants activity of disinfectants (conted)(conted) 3. 3. May be inactivated May be inactivated by by

– DirtDirt– Organic matter : Proteins, Pus, Blood, Mucus and Organic matter : Proteins, Pus, Blood, Mucus and

Faeces.Faeces.– Non organic: Cork, and Some plastics.Non organic: Cork, and Some plastics.

4. 4. TimeTime : Disinfectants need time to work. : Disinfectants need time to work. 5. 5. Range of Action Range of Action : Disinfectants not equally : Disinfectants not equally

effective against the whole spectrum of effective against the whole spectrum of microbes. e.g. microbes. e.g. ChlorhexidineChlorhexidine less active less active against GNB than Gram positive cocci.against GNB than Gram positive cocci.

HypochloritesHypochlorites and and GluteraldehydeGluteraldehyde are more are more active against hepatitis viruses than most active against hepatitis viruses than most other disinfectants.other disinfectants.

DisinfectanDisinfectanttGPCGPC

Activity againstActivity against

TBTB

Inactivated byInactivated byCorrosiveCorrosive

ActionActionGNBGNBSporesSporesProteinProteinSoapSoap

PhenolicsPhenolicsSudolSudol

++++++++__++++__++

IzalIzal++++++++____++____

SolubleSolublePhenolic*Phenolic*e.g. clearsole.g. clearsol

++++++++__++++__++ toto+ +

ChlorineChlorinecompoundcompound

++++++++++++++++++__ ++ ++oror + + (buffered (buffered SolutionSolution))

LodophorLodophor++++++++++(Slow)(Slow)

++++____

ChorhexidineChorhexidine(Hibitane)(Hibitane)

++++++__________

70°70° alcoholalcohol++++++++__++++++____

FormaldehydeFormaldehyde++++++++++++(slow)(slow)

++++++__++++

GlutaraldehydeGlutaraldehyde(Cidex)(Cidex)

++++++++++++++++++__++

Hospital disinfection Hospital disinfection methodsmethodsArticle Article DisinfectantDisinfectant Floors, walls Phenolics fluids 1-2%Floors, walls Phenolics fluids 1-2% Surfaces tables Hypochloride, Alcohol Surfaces tables Hypochloride, Alcohol skin:skin: SurgeonsSurgeons’’hands Chlorhexidine, Iodinehands Chlorhexidine, Iodine alcoholalcohol Patient skin 70% Alcohol, IodinePatient skin 70% Alcohol, Iodine Endoscopes Gluteraldehyde 2%Endoscopes Gluteraldehyde 2% (Cidex), subatmospheric (Cidex), subatmospheric steamsteam Thermometers 70% Alcohol Thermometers 70% Alcohol


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