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STERILIZATION STERILIZATION & & DISINFECTION DISINFECTION PRESENTER –DR ANSHU PRESENTER –DR ANSHU J.SS. MEDICAL COLLEGE J.SS. MEDICAL COLLEGE MYSORE MYSORE

Sterilization 2

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Page 1: Sterilization 2

STERILIZATIONSTERILIZATION&&

DISINFECTIONDISINFECTION

PRESENTER –DR ANSHUPRESENTER –DR ANSHU

J.SS. MEDICAL COLLEGEJ.SS. MEDICAL COLLEGE

MYSOREMYSORE

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DefinitionsDefinitions

• Sterilization-defined as the process by which an Sterilization-defined as the process by which an article, surface or medium is freed of all micro article, surface or medium is freed of all micro organisms either in the vegetative or spore stateorganisms either in the vegetative or spore state

• Disinfection-defined as destruction or removal of Disinfection-defined as destruction or removal of all pathogenic organismsall pathogenic organisms

• Decontamination-refers to the process of rendering Decontamination-refers to the process of rendering an article or area free of danger from an article or area free of danger from contaminants,includin g contaminants,includin g microbial,chemical,radioactive & other hazardsmicrobial,chemical,radioactive & other hazards

• Bactericidal agents or germicides-are chemicals Bactericidal agents or germicides-are chemicals which are able to kill bacteriawhich are able to kill bacteria

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• Bacteriostatic agents-are chemicals that only Bacteriostatic agents-are chemicals that only prevent the multiplication of bacteria which may, prevent the multiplication of bacteria which may, however remain alivehowever remain alive

• Antisepsis-The term “antisepsis” is used to indicate Antisepsis-The term “antisepsis” is used to indicate the prevention of infection,usually by inhibiting the the prevention of infection,usually by inhibiting the growth of bacteria in wounds or tissuegrowth of bacteria in wounds or tissue

• Antiseptics-chemical disinfectants that can be Antiseptics-chemical disinfectants that can be safely applied on skin or mucous membrane & safely applied on skin or mucous membrane & used to prevent infection by inhibiting the growth used to prevent infection by inhibiting the growth of bacteriaof bacteria

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Applications in Applications in microbiology microbiology laboratory laboratory• Sterilization of culture media, reagents & Sterilization of culture media, reagents &

equipments before their use in laboratoryequipments before their use in laboratory

• Effective decontamination of spillage,surfaces & Effective decontamination of spillage,surfaces & equipment after useequipment after use

• Disinfection of contaminated material before their Disinfection of contaminated material before their safe disposal from laboratory safe disposal from laboratory

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PHYSICAL METHODS OF STERILIZATIONPHYSICAL METHODS OF STERILIZATION

HEAT:considered to be the most reliable method for HEAT:considered to be the most reliable method for articles that can withstand heatarticles that can withstand heat

Dry heat Moist heatDry heat Moist heatM.O.A.-M.O.A.- Dry Heat- Protein denaturation,Dry Heat- Protein denaturation, Oxidative damage,Oxidative damage, Toxic effects of elevated levels of Toxic effects of elevated levels of electolytes electolytes Moist Heat-Coagulation & denaturation of protein Moist Heat-Coagulation & denaturation of protein Thermal death timeThermal death time-Minimum time reqd to kill a -Minimum time reqd to kill a

suspension of organisms at a predetermined suspension of organisms at a predetermined temperature in a specific environment temperature in a specific environment

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Factors affecting sterilization by heatFactors affecting sterilization by heat

• Nature of heat-Moist heat is more effective than dry heatNature of heat-Moist heat is more effective than dry heat

• Temp&time-Temp is inversely proportional to time. Temp&time-Temp is inversely proportional to time.

As temp increases,time taken decreasesAs temp increases,time taken decreases

• Number of microorganism-More the no. of organisms,higher Number of microorganism-More the no. of organisms,higher the temp.or longer the duration reqd the temp.or longer the duration reqd

• Nature of micro-organism-Spores are highly resistant to heatNature of micro-organism-Spores are highly resistant to heat

• Type of material-Heavily contaminated articles req higher Type of material-Heavily contaminated articles req higher temp or prolonged exposuretemp or prolonged exposure

Certain heat sensitive articles must be sterilized at lower Certain heat sensitive articles must be sterilized at lower temptemp

• Presence of organic material [protein,sugar,oils,fat]-Increases Presence of organic material [protein,sugar,oils,fat]-Increases the time reqdthe time reqd

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Dry HeatDry Heat

METHODMETHOD ARTICLE ARTICLE STERILIZEDSTERILIZED

LIMITATIONSLIMITATIONS

A)RED HEATA)RED HEAT Bacteriological Bacteriological loops,straight loops,straight wires,tips of wires,tips of forceps,searing forceps,searing spatulas spatulas

Only for those Only for those articles that can be articles that can be heated to redness in heated to redness in flameflame

B)FLAMINGB)FLAMING Scalpels,Scalpels,

mouth of test tubes,mouth of test tubes,

flasks, glass slides,flasks, glass slides,

coverslipscoverslips

•only for articles that only for articles that can be exposed to can be exposed to flame, no guarantee flame, no guarantee of killing spores,of killing spores,

Cracking of Cracking of glassware may occur glassware may occur

C)INCINERATIOC)INCINERATIONN

Soiled Soiled dressings,animal dressings,animal carcasses,pathologicarcasses,pathological material,beddingcal material,bedding

Technique results in Technique results in loss of article,only loss of article,only suitable suitable for suitable suitable for the articles that have the articles that have to be disposedto be disposed

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HOT AIR OVENHOT AIR OVEN

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HOT AIR OVENHOT AIR OVEN• Most widely used method of sterilizationMost widely used method of sterilization by dry by dry

heatheatPrinciplePrinciple--• Articles to be sterilized are exposed to high Articles to be sterilized are exposed to high

temp.for a duration of one hour in an electrically temp.for a duration of one hour in an electrically heated ovenheated oven

• Since air is a poor conductor of heat ,even Since air is a poor conductor of heat ,even distribution of heat throughout the chamber is distribution of heat throughout the chamber is achieved by fanachieved by fan

• Heat is transferred to the article by radiation, Heat is transferred to the article by radiation, conduction & convection conduction & convection

Sterilization cycle-Sterilization cycle-Time taken for articles to reach sterilizing temp Time taken for articles to reach sterilizing temp ++Maintainence of sterilizing temp.for a defined Maintainence of sterilizing temp.for a defined

period(holding time) period(holding time) ++Time taken for articles to cool downTime taken for articles to cool down

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Different temp-time relationshipDifferent temp-time relationship for for holding time:holding time:

60min at 160 degree celsius60min at 160 degree celsius

40min at 170 degree celsius40min at 170 degree celsius

20min at 180 degree celsius20min at 180 degree celsius

Increasing temp. by 10 degrees Increasing temp. by 10 degrees shortens the sterilizing time by 50% shortens the sterilizing time by 50%

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Precautions during sterilization Precautions during sterilization processprocess Articles to be sterilized must be perfectly dry Articles to be sterilized must be perfectly dry

before placing them inside to avoid breakagebefore placing them inside to avoid breakageArticles must be placed at sufficient distance, so Articles must be placed at sufficient distance, so

as to allow free circulation of air in betweenas to allow free circulation of air in betweenMouths of flasks,test tubes & both ends of pipettes Mouths of flasks,test tubes & both ends of pipettes

must be plugged with cotton woolmust be plugged with cotton woolArticles such as petridishes & pipettes may be Articles such as petridishes & pipettes may be

arranged inside metal canisters& then placedarranged inside metal canisters& then placedIndividual glass articles must be wrapped in kraft Individual glass articles must be wrapped in kraft

paper or aluminium foilpaper or aluminium foilHot air oven must not opened until the temp inside Hot air oven must not opened until the temp inside

has fallen below 60*C to prevent breakage of has fallen below 60*C to prevent breakage of glasswaresglasswares

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AdvantagesAdvantages Effective method of Effective method of

sterilization of heat sterilization of heat stable articlesstable articles

Articles remain dry Articles remain dry after sterilizationafter sterilization

Only method of Only method of sterilizing oils & sterilizing oils & powderspowders

DisadvantagesDisadvantagesHot air has poor Hot air has poor

penetration (poor penetration (poor conductor of heat)conductor of heat)

Cotton wool & paper Cotton wool & paper may get slightly charredmay get slightly charred

Glasses may become Glasses may become smokysmoky

Takes longer time Takes longer time compared to autoclavecompared to autoclave

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Sterilization controlSterilization control

Physical - Temperature chart recorderPhysical - Temperature chart recorder

- Thermocouple - Thermocouple

Chemical- Brownie’s tube no-3 [green spot]Chemical- Brownie’s tube no-3 [green spot]

Biological- 10*6 spores of Bacillus subtilis var Biological- 10*6 spores of Bacillus subtilis var nigerniger

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MOIST HEAT STERILIZATIONMOIST HEAT STERILIZATION

METHODMETHOD TEMP-TIMETEMP-TIME USESUSES ORGANISMS ORGANISMS AFFECTEDAFFECTED

PASTEURIZATIPASTEURIZATIONON

Holder method-Holder method-63*CX30min63*CX30min

Flash method-Flash method-72*C X15-20 72*C X15-20 sec f/b quickly sec f/b quickly cooling to 13*Ccooling to 13*C

Food Food & & dairy dairy industindustryry

Salmonella, Salmonella, mycobacteria, mycobacteria, streptococci, streptococci, staphylococci, staphylococci, brucella-destroyed brucella-destroyed coxiella may coxiella may survivesurvive

VACCINE BATH VACCINE BATH 60*C X1 hr60*C X1 hr ContaContaminatiminating ng bacterbacteria in ia in vaccinvaccine e preparpreparationation

Only vegetative Only vegetative bacteria are killed bacteria are killed spores survivespores survive

At temp.below 100*C

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WATER BATH OR WATER BATH OR SERUM BATHSERUM BATH

56*CX1Hr on 56*CX1Hr on several several successive successive days[proteindays[proteins in the s in the serum will serum will coagulate at coagulate at higher temp]higher temp]

ContamiContaminating nating bacteria bacteria in serum in serum preparatpreparationion

only only vegetative vegetative bacteria are bacteria are killed killed spores spores survivesurvive

INSPISSATIONINSPISSATION 80-85*C X30 80-85*C X30 Min on 3 Min on 3 successive successive daysdays

Egg & Egg & serum serum containicontaining ng media media [L-J [L-J Media Media &Loeffle&Loeffler’s r’s serumserum

Day1-Day1-vegetative vegetative forms are forms are killed, spores killed, spores germinate by germinate by next day & are next day & are killed killed Success of the Success of the process process depends on depends on germination of germination of spores spores

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At temp.100*CAt temp.100*CBoiling:Boiling:

• Boiling water at 100*C for 10-20 minutesBoiling water at 100*C for 10-20 minutes

• Articles-certain metal articles & glasswaresArticles-certain metal articles & glasswares

• Most vegetative bacteria and viruses are killed immediatelyMost vegetative bacteria and viruses are killed immediately Not effective against - Bacterial toxinsNot effective against - Bacterial toxins

- spores- sporesSteam at 100*CSteam at 100*C

• Principle Principle :Exposing articles to free steam at 100*C:Exposing articles to free steam at 100*C

• Eg-Arnold’s and Koch’s steamerEg-Arnold’s and Koch’s steamer

An Autoclave (with discharge tap open)An Autoclave (with discharge tap open)

• Exposure period- 90 minutesExposure period- 90 minutes

• Uses-Media such as TCBS, DCA, Selenite brothUses-Media such as TCBS, DCA, Selenite broth

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Tyndallisation Tyndallisation OR OR Fractional sterilization OR Intermittent Fractional sterilization OR Intermittent sterilizationsterilization

Sugar and gelatin in the medium may get Sugar and gelatin in the medium may get decomposed on autoclaving, hence they are decomposed on autoclaving, hence they are exposed to free steaming for 20min on 3 exposed to free steaming for 20min on 3 successive dayssuccessive days

Success of the process depends on germination Success of the process depends on germination of sporesof spores

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At temp.>100*CAt temp.>100*C

AUTOCLAVE / STEAM STERILIZATIONAUTOCLAVE / STEAM STERILIZATIONPrinciple Principle - [steam under pressure]- [steam under pressure] Water boils when its vapour pressure equals that Water boils when its vapour pressure equals that

of surrounding atmospheric pressure.of surrounding atmospheric pressure. When pressure inside the closed vessel When pressure inside the closed vessel

increases,the temp at which water boils also increases,the temp at which water boils also increasesincreases

At a pressure of 15Lbs inside autoclave, the temp At a pressure of 15Lbs inside autoclave, the temp is said to be 121*Cis said to be 121*C

Exposure of articles to this temp for 15 minutes Exposure of articles to this temp for 15 minutes sterilizes themsterilizes them

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Articles sterilizedArticles sterilized

• Culture mediaCulture media

• Hospital dressingsHospital dressings

• LinenLinenAdvantages of steamAdvantages of steam::

• More penetrative More penetrative power than steampower than steam

• Moistens Moistens spores[essential for spores[essential for coagulation of proteins]coagulation of proteins]

Different types of Different types of autoclave:autoclave:

• Simple pressure Simple pressure cooker typecooker type

• Steam jacketed Steam jacketed downward downward displacement displacement laboratory autoclavelaboratory autoclave

• High pressure High pressure

pre-vaccum autoclavepre-vaccum autoclave

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PrecautionsPrecautions

Articles should not be tightly packedArticles should not be tightly packed Autoclave must not be overloadedAutoclave must not be overloaded Air discharge must be complete and there should Air discharge must be complete and there should

not be any residual air trapped insidenot be any residual air trapped inside Caps of bottles & flasks should not be tightCaps of bottles & flasks should not be tight Autoclave must not be opened until the pressure Autoclave must not be opened until the pressure

has fallen else the contents will boil overhas fallen else the contents will boil over Articles must be wrapped in paper to prevent Articles must be wrapped in paper to prevent

drenchingdrenching Bottles must not be overfilledBottles must not be overfilled

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Advantages Advantages DisadvantagesDisadvantages

Very effective way of Very effective way of sterilizationsterilization

Quicker than hot air Quicker than hot air ovenoven

Drenching and wetting Drenching and wetting of articlesof articles

Trapped air may Trapped air may reduce efficacyreduce efficacy

Takes long time to Takes long time to coolcool

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Sterilization control Sterilization control

PHYSICAL : Automatic process controlPHYSICAL : Automatic process control

ThermocoupleThermocouple

Temperature chart recorderTemperature chart recorderCHEMICAL: Brownie’s tube no 1[black spot]CHEMICAL: Brownie’s tube no 1[black spot]

Succinic acid(Melting point -121*C)Succinic acid(Melting point -121*C)

Bowie’s Dick tape(satisfactory Bowie’s Dick tape(satisfactory

process-dark brown stripes)process-dark brown stripes)BIOLOGICAL: 10*6 spores of GeobacillusBIOLOGICAL: 10*6 spores of Geobacillus

stearothermophillusstearothermophillus

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RADIATIONRADIATIONNON-IONISING RADIATIONNON-IONISING RADIATION

U.V. RAYSU.V. RAYS[200-280nm]:260nm most effective[200-280nm]:260nm most effective M.O.A.-Formation of thymine-thymine dimersM.O.A.-Formation of thymine-thymine dimers Inhibition of D.N.A replicationInhibition of D.N.A replication Uses-to disinfect hospital wards,operation theatres,virus Uses-to disinfect hospital wards,operation theatres,virus

laboratorieslaboratories Limitation:do not kill sporesLimitation:do not kill spores Disadvantages : Low penetrative powerDisadvantages : Low penetrative power Limited life of U.V. bulbLimited life of U.V. bulb Some bacteria have D.N.A.repair enzymesSome bacteria have D.N.A.repair enzymes overcome damageovercome damage Organic matter and dust prevents its reachOrganic matter and dust prevents its reach Rays are harmful to skin & eyesRays are harmful to skin & eyes Doesn’t penetrate papers, plastics or glassDoesn’t penetrate papers, plastics or glass

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INFRA-RED RAYSINFRA-RED RAYS

M.O.A.- Generation of heatM.O.A.- Generation of heat Temp 180*C X 7.5 minutesTemp 180*C X 7.5 minutes

Articles sterilized : metallic instruments, Articles sterilized : metallic instruments, glasswaresglasswares

Mainly used in central sterile supply departmentMainly used in central sterile supply department

Sterilization control:Brownie’s tube no.4(blue Sterilization control:Brownie’s tube no.4(blue spot)spot)

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IONIZING RAYS IONIZING RAYS [COLD STERILIZATION[COLD STERILIZATION]]

Particulate [electron Particulate [electron beams]beams]

Syringes, gloves ,dressing Syringes, gloves ,dressing packs ,food & packs ,food & pharmaceuticalspharmaceuticals

Few seconds onlyFew seconds only

DisadvantagesDisadvantages--

Poor penetrative power,req Poor penetrative power,req sophisticated equipmentssophisticated equipments

Not widely used in Not widely used in medicinemedicine

Electromagnetic Electromagnetic rays[Gamma rays & X rays[Gamma rays & X rays]rays]

Damage nucleic acid of Damage nucleic acid of microorganismmicroorganism

Used comercially to Used comercially to sterilize disposable sterilize disposable petridishes, plastic petridishes, plastic syringes, antibiotics, syringes, antibiotics, vitamins & hormonesvitamins & hormones

Dose of 2.5 megarads kills Dose of 2.5 megarads kills all bacteria. fungi,viruses & all bacteria. fungi,viruses & sporesspores

Longer time of exposureLonger time of exposure Disadvantages: can’t be Disadvantages: can’t be

switched off, glasswares switched off, glasswares become brownish, loss of become brownish, loss of tensile strength of fabricstensile strength of fabrics

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FILTRATIONFILTRATION

To remove microbes To remove microbes from heat labile from heat labile liquids :Serumliquids :Serum

Antibiotic solutionsAntibiotic solutions Sugar solutionSugar solution Urea solutionUrea solution• Applications:Applications: Removing Removing bacteria from bacteria from

ingredients of culture ingredients of culture media,media,

• Preparing suspensions Preparing suspensions of viruses,of viruses,

• Water purification Water purification

Types of filterTypes of filter:: Earthenware filtersEarthenware filters Pasteur-Pasteur-

ChamberlandChamberland BerkefeldBerkefeld MandlerMandler Asbestos filtersAsbestos filters Sintered glass filterSintered glass filter Membrane filterMembrane filter

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AIR FILTERSAIR FILTERS

Air can be filtered using Air can be filtered using HEPA [High efficiency particle HEPA [High efficiency particle air filter]air filter]

99.97%efficient for removing particles >0.3micrometers 99.97%efficient for removing particles >0.3micrometers in diameterin diameter

ApplicationsApplications:Rooms having severe neutropenic patients,:Rooms having severe neutropenic patients,

Operating rooms for orthopaedic implant procedureOperating rooms for orthopaedic implant procedure

Efficiency tested Efficiency tested : Dioctylphthalate (DOP) particle test : Dioctylphthalate (DOP) particle test using particles that are 0.3 micrometers in diameterusing particles that are 0.3 micrometers in diameter

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Chemical MethodsChemical Methods

Ideal disinfectant :Ideal disinfectant : should have should have• Wide spectrum of activityWide spectrum of activity• Destroy microbes within practical period of timeDestroy microbes within practical period of time• Active in the presence of organic matterActive in the presence of organic matter• Active at any pHActive at any pH• StableStable• Long shelf lifeLong shelf life• High penetrating powerHigh penetrating power• Non-toxic, non-allergenic, non-irritative or non-Non-toxic, non-allergenic, non-irritative or non-

corrosivecorrosive

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• Should not have bad odourShould not have bad odour

• Should not leave non-volatile residue or stainShould not leave non-volatile residue or stain

• Efficacy should not be lost on reasonable dilutionEfficacy should not be lost on reasonable dilution

• Should not be expensiveShould not be expensive

• Easily availableEasily available

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Factors determining potency of Factors determining potency of disinfectantdisinfectant

• Concentration of substanceConcentration of substance

• Time of actionTime of action

• pH of the mediumpH of the medium

• TemperatureTemperature

• Nature of organismNature of organism

• Presence of extraneous materialPresence of extraneous material

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CLASSIFICATION OF DISINFECTANTSCLASSIFICATION OF DISINFECTANTS

A)Based on consistencyA)Based on consistency

Liquid Liquid [Alcohols,Phenol][Alcohols,Phenol]

Gaseous Gaseous [Formaldehyde [Formaldehyde vapour,Ethylene vapour,Ethylene oxide]oxide]

B)Based on spectrum of B)Based on spectrum of activityactivity

High levelHigh level

Intermediate levelIntermediate level

Low levelLow level

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C)Based on mechanism of actionC)Based on mechanism of action

• Action on membrane[Alcohol, Detergents]Action on membrane[Alcohol, Detergents]

• Denaturation of cellular proteins[Alcohol, Denaturation of cellular proteins[Alcohol, Phenol]Phenol]

• Oxidation of essential groups of Oxidation of essential groups of enzymes[Halogen,H2O2]enzymes[Halogen,H2O2]

• Alkylation of amino, carboxyl & hydroxyl Alkylation of amino, carboxyl & hydroxyl group[Ethylene oxide,Formaldehyde]group[Ethylene oxide,Formaldehyde]

• Damage to nucleic acid [Ethylene Damage to nucleic acid [Ethylene oxide,Formaldehyde]oxide,Formaldehyde]

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Spectrum of activitySpectrum of activityVegetative cells

mycobacteria

spores fungi viruses

examples

High level

+ + + + + Ethylene oxide,Gluteraldehyde,Formaldehyde

Intermediate level

+ + - + + Phenolics,Halogens

Low level

+ - - + +/- Alcohols,Quaternary ammonium compounds

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Alcohols Alcohols

Ethyl alcohol & isopropyl alcohol[preferred] Ethyl alcohol & isopropyl alcohol[preferred] M.O.A.-Denaturation of bacterial proteinsM.O.A.-Denaturation of bacterial proteins Concentration of 60-90% in waterConcentration of 60-90% in water No action on sporesNo action on spores Application-Disinfection of clinical thermometersApplication-Disinfection of clinical thermometers Methyl alcohol-Effective against fungal spores,Methyl alcohol-Effective against fungal spores,

To treat cabinets & incubators To treat cabinets & incubators affected byaffected by

themthem

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Aldehydes Aldehydes

FormaldehydeFormaldehyde

• Active against amino group Active against amino group in protein moleculein protein molecule

• Bactericidal,sporicidal,lethal Bactericidal,sporicidal,lethal effects on viruseseffects on viruses

• Applications-Applications-Preserve anatomical Preserve anatomical

specimensspecimens10% formalin containing 10% formalin containing

0.5%sodium tetraborate is 0.5%sodium tetraborate is used to sterilize metal used to sterilize metal instrumentsinstruments

GlutaraldehydeGlutaraldehyde

• Specially effective against Specially effective against tubercle bacilli,fungi & tubercle bacilli,fungi & virusesviruses

• Application-Application-Corrugated rubber Corrugated rubber

anaesthetic tubes,face anaesthetic tubes,face masks,plastic ET Tube, metal masks,plastic ET Tube, metal instruments,cystoscopes,broinstruments,cystoscopes,bronchoscopesnchoscopes

Less toxic & irritant to eyes Less toxic & irritant to eyes & skin than formaldehyde& skin than formaldehyde

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DyesDyes

• Aniline dyes Acridine dyesAniline dyes Acridine dyesBrilliant green ProflavineBrilliant green Proflavine

Malachite green AcriflavineMalachite green Acriflavine

Crystal violet Euflavine Crystal violet Euflavine

AminacrineAminacrine

• Mainly bacteriostatic, low bactericidal activityMainly bacteriostatic, low bactericidal activity

• No activity against tubercle bacilli, hence the use of No activity against tubercle bacilli, hence the use of malachite green in L-Jmediamalachite green in L-Jmedia

• More effective against gram positive bacteria than gram More effective against gram positive bacteria than gram negative bacterianegative bacteria

• Use-Skin & wound antisepticsUse-Skin & wound antiseptics

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HalogensHalogens

IodineIodine

• Skin disinfectantSkin disinfectant

• Actively Actively bactericidal,with bactericidal,with moderate action moderate action against sporesagainst spores

• Active against Active against tubercle bacilli & tubercle bacilli & virusesviruses

Chlorine[hypochlorites]Chlorine[hypochlorites]

• Markedly bactericidalMarkedly bactericidal

• Wide spectrum of Wide spectrum of action against virusesaction against viruses

• Organic chloramine-Organic chloramine-antiseptics for antiseptics for dressing woundsdressing wounds

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PhenolsPhenols

• Lysol,cresol,chlorophenols,chloroxyphenols,chlorhLysol,cresol,chlorophenols,chloroxyphenols,chlorhexidineexidine

• M.O.AM.O.A.-cell membrane damage.-cell membrane damagerelease cell release cell contentscontents lysis lysis

Precipitate proteinPrecipitate protein Inactivation of membrane bound oxidases & Inactivation of membrane bound oxidases &

dehydrogenases dehydrogenases

• Chlorhexidine-skin antisepticChlorhexidine-skin antiseptic

• Most effective against gram positive organismsMost effective against gram positive organisms

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GasesGases

Ethylene oxide Formaldehyde gas

Betapropiolactone

Alkylating the amino, carboxyl,hydroxyl & sulphydryl gps in protein moleculeReacts with DNA & RNAApplications-Heart-lung machines,ventilators,sutures,dental equipmentsEffective against all type of microorganisms including viruses and sporesMutagenic & carcinogenic

Alkylation of amino group

Applications- Operation theatres,sick rooms,laboratories

Alkylation of carboxyl & hydroxyl groups

More efficient than formaldehyde for fumigation

Active against all organisms & virusescarcinogenic

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Surface active agentsSurface active agents

• M.O.AM.O.A.- Alter the energy relationship at interface .- Alter the energy relationship at interface producing a reduction of surface or interfacial tensionproducing a reduction of surface or interfacial tension

• Most important are cationic surface active agents in the Most important are cationic surface active agents in the form of quaternary ammonium compoundsform of quaternary ammonium compounds

[acetyl,trimethylammonium bromide(CETAVLON OR [acetyl,trimethylammonium bromide(CETAVLON OR CETRIMIDE)]CETRIMIDE)]

• Bactericidal, more active against gram positive bacteriaBactericidal, more active against gram positive bacteria

• No action on spores, tubercle bacilli,& most virusesNo action on spores, tubercle bacilli,& most viruses

• Disadvantage- Disadvantage- Pseudomonas can metabolise Pseudomonas can metabolise cetrimide,using them as a carbon, nitrogen & energy cetrimide,using them as a carbon, nitrogen & energy sourcesource

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Metallic saltsMetallic salts

• Salts of silver, copper and mercurySalts of silver, copper and mercury

• M.O.AM.O.A.-protein coagulation.-protein coagulation

• Capacity to combine with free sulphydryl group of Capacity to combine with free sulphydryl group of cell enzymescell enzymes

• Thiomersal,phenylmercury nitrate & Thiomersal,phenylmercury nitrate & mercurochrome-mild antisepticsmercurochrome-mild antiseptics

• Marked bacteriostatic actionMarked bacteriostatic action

• Copper salts -fungicidesCopper salts -fungicides

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Testing of DisinfectantsTesting of Disinfectants

• No single test is available to determine the No single test is available to determine the efficiency of a disinfectantefficiency of a disinfectant

• Different methods-Different methods- Koch’s methodKoch’s method Rideal walker methodRideal walker method Chick Martin testChick Martin testKelsey-Sykes test [capacity to use dilution test]Kelsey-Sykes test [capacity to use dilution test]I n-use testI n-use test

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NEWER METHODS OF NEWER METHODS OF STERILIZATION AND STERILIZATION AND DISINFECTIONDISINFECTION

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Process Agent

Disinfection

Ortho-phthaladehyde(Cidex OPA)Antimicrobial coating(Surfacine)Superoxide water(Sterilox)

Sterilization

Liquid sterilization process(Endoclens)Rapid readout ethylene oxide biological indicator(Attest)New plasma sterilizer(Sterrad 50)

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COMPARISON OF NEW AND STANDARD COMPARISON OF NEW AND STANDARD DISINFECTION & STERILIZATION DISINFECTION & STERILIZATION TECHNOLOGIESTECHNOLOGIES

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New Standard Advantages Disadv. Future needs

OPA Glutaralehyde

Shorter process time(12vs45min)No activationNot a known irritant to eyes pr nasal passagesNo vapour ceiling limitWeak odour

Stains protein grayHigher cost

Additional studies of antimicrobial efficacyCost-effectiveness studiesStudy of effectiveness in actual clinical useVerification of more cycles per solution than glutaraldehyd

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Surfacine

Disinfectants (phenolics,quaternary ammonium)Antiseptics (alcohol,chlorhexidine)

Antimicrobial persistance (>13days)May be used on animate or inanimate objectsBroad antimicrobial spectrumNo toxigenicity to mammalian cellTransfers active agent (silver) to microbes on demand without elution

Cost?

Assess microbicidal activity against broad spectrum of pathogensDemonstration of efficacy to reduce nosocomial infectionHuman safety & toxicity data for use as an antisepticDemonstrate antimcrobial activity in presence of organic matter

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Superoxide water

High or low level disinfectants;antiseptics

Basic materials (saline & electricity)inexpensiveEnd product not damaging to environmentNon toxic to biological tissues

Production equipment inexpensive due to monitoringDecreased efficacy in presence of organic matterLimited use life(must be freshly prepared)

Cost-effectiveness study

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Endoclens

None

Device automatically cleans & sterilizesRapid cycle time(<30min)Tests endoscope for channel blockage &leaksAdvantages of automated process(consistant exp. to sterilant,operator convenience)

•Cost?•Used for immersible in struments only•No long term storage

•Cost.effectiveness study•Study of eff. In actual clinical use•Assessment of microbicidal activity

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EO rapid read out

48-hr spore readout biological indicator

Rapid(4hr)reliable assessment of sterilizationn efficacyPrevents recall of released sterilization loads

Cost?Not tested with EO and CO2 mixtures

Cost-effectiveness studyValidation of claimed 100% sensitivity

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Plasma sterilizer

Hydrogen peroxide gas plasma sterilizer

Use of two H2O2 diffusion plasma stage cycles is a more effective sterilization processReduced cycle timeVarious sized units availableLeaves no toxic residue

Cost?Endoscopes with length >40cm or diameter<3mm cannot be processed

Cost-effectivenes studyStudy of effectiveness in actual practice

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Conclusion Conclusion

• Various methods of sterilization & disinfection are Various methods of sterilization & disinfection are availableavailable

• Use of a particular method depends upon the Use of a particular method depends upon the article to be sterilized and nature of article to be sterilized and nature of microorganismmicroorganism

• Newer sterilization and disinfection technologies Newer sterilization and disinfection technologies may provide significant advantages over existing may provide significant advantages over existing technologiestechnologies

• These new technologies hold the promise of These new technologies hold the promise of improved patient careimproved patient care

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ReferencesReferences

** Practical Medical Microbiology,Practical Medical Microbiology,

Mackie & McCartney,14Mackie & McCartney,14thth edition edition

** Text book of Microbiology, Text book of Microbiology,

Ananthnarayan & Paniker’s,8Ananthnarayan & Paniker’s,8thth edition edition

** Internet sources Internet sources

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Thank Thank youyou