Sterilization&Disinfection

PROF. HANAN HABIB

DEPARTMENTOF PATHOLOGY &LABORATORY MEDIC INE

COLLEGEOF MEDIC INE-KSU

Objectives

1-Define the terms sterilization, disinfectant and antiseptic.2- Know the different methods of sterilization (physical and chemical methods).3- Know and realizes that heat is the most important method of sterilization and its application in medical practice.4-Know dry heat as applied in hot air oven and moist heat as applied in Autoclaves.5- Know the principles of Autoclave function and monitoring methods of sterilization .6- Know the importance of non heat sterilization methods and their use for sterilization of heat sensitive objects.

Objectives,cont.

7-Know the differences between antiseptics and disinfectants.8- Know the factors affecting disinfectants and antiseptics .9- Know the scope of function and applications of different disinfections and antiseptics in clinical practice.

DefinitionsSterilization: completekillingofallformsofmicroorganisms,includingbacterialsporesDisinfection: killingorremovingofharmfulvegetativemicroorganisms.Disinfectant: chemicalsubstanceusedoninanimateobjects.Toxictohuman.Antiseptic:disinfectantthatcanbesafelyusedonlivingtissues.

MethodsofSterilization1. PhysicalMethods:

Heat(moistheat&dryheat)

U.V.(ultraviolet)Light

IonizingRadiation

Filtration

2.ChemicalMethods:(usedforheatsensitiveequipment)

Ethyleneoxide

Gluteraldehyde

PhysicalMethods:HeatHEAT :Mostimportantmethod,should

beusedwheneverpossible, canbe:A-Dryheat:use temperatureat160˚Cfor

onehourB- Moistheat:eg.Autoclaves,use

temperatureat121for15minutesor134Cfor10minutes.

Physicalmethods:RadiationU.V.light◦ Haslimitedsterilizingpowerbecauseofpoorpenetrationintomostmaterials.Generallyusedinirradiationofairincertainareassuchasoperatingrooms,virology andtuberculosis labs.

Ionizingradiation◦ e.g.Gammaradiation:hasgreaterenergythanU.V.light,thereforemoreeffective.Usedmainlyinindustrialfacilitiese.g.sterilizationofdisposableplasticsyringes,gloves,specimens,containersandPetridishes.

PhysicalMethods:FiltrationUseofmembranefiltermadeofcelluloseacetateorothermaterial.

Generallyremovesmostbacteriabutvirusesandsomesmallbacteria(e.g.Chlamydia &Mycoplasma) requiresmallerporesizes.

Thusfiltrationdoesnottechnicallysterilizetheitemsbutisadequateforcircumstancesunderwhichisused.

Mainuse:forheatlabilesubstancese.g.sera,antibiotics.Otheruse:ACofcertainoperatingtheatres.

MedicalapplicationsofheatmethodsDryHeat

DryHeat- killsmicroorganismsbydestroyingtheiroxidativeprocesses.◦ Simplestmethodisexposingitemtobesterilizedtothenakedflamee.g.Bunsenburner- forsterilizingbacteriologicalloops,knives,blades.

◦ Hotairovenexposeitemsto160°Cfor1hour.

Haselectricelementinchamberassourceofheatplusafan tocirculateairforevendistributionofheatinchamber.Ovenwithoutfanisdangerous.Usedforitemsthatarelackingwatersuchas:-Metals-Glassware-Ointment,Oil,Waxes,Powder

MoistHeat:Autoclave

Useshotwater.Moistheatkillsmicroorganismsbydenaturating proteins.

Autoclaving : thestandardsterilizationmethodinhospitals.

TheequipmentiscalledAutoclave anditworksunderthesameprincipleasthepressurecookerwherewaterboilsatincreasedatmosphericpressure,becauseofincreasedpressure theboilingpointofwateris>100°C.

TheAutoclave isatoughdoublewalledchamberinwhichairisreplacedbypuresaturatedsteamunderpressure.

Air inthechamberisevacuatedandfilledwithsaturatedsteam.Thechamberisclosedtightly,thesteamkeepsonfillingintoitandthepressuregraduallyincreases.Theitemstobesterilizedcompletelysurroundedbysaturatedsteam(moistheat)whichoncontactwiththesurfaceofmaterialtobesterilizedcondenses toreleaseitslatentheatofcondensationwhichaddstoalreadyraisedtemperatureofsteamsothateventuallyallthemicroorganismsandsporesarekilled.

Theusualtemperatureachievedis121°Cfor15minutesor 134Cfor10minutes.

AdvantagesofAutoclaves

Temp>100Cthereforesporeskilled.Condensationofsteamgeneratesextraheat.

Thecondensationalsoallowsthesteamtopenetrate intoporousmaterials.Note:Autoclavable itemsmustbeusedforinvasiveproceduresinoperatingroom,dentalequipments,andthelaboratories.

MonitoringofAutoclaves

1.Physicalmethod:usethermocoupletomeasureaccuratelythetemperature.2.Chemicalmethod: useheatsensitivechemicalthatchangescolorattherighttemperatureandexposuretime.

e.g.a)Autoclavetape(commonlyused)b)Browne’stube.

3.Biologicalmethod:sporetest,akitcontainingasporebearingorganismisaddedduringthesterilizationprocess,thenculturedlaterontoensurethatsporeshavebeenkilled.

Sporetest(Biologicalindicator)

Moistheat:otherapplications.PasteurizationUsedheatattemperaturessufficienttoinactivateharmfulorganisminmilk(includingmostviruses,mostvegetativebacteriaandfungi).Thetemperaturesofsterilizationisnotachieved.Twomethods:Flashmethod:Temp.used74°Cfor3-5seconds.Conventionalmethod:temp.used62°Cfor30minutes..Boiling: commonlyusedindomesticcircumstances.Doesnotkillspores..Steamsterilizers: tosterilizebabiesbottles.

PasteurizationofmilkTopreventtransmissionofthefollowingimportantzoonoticdiseasestohuman:qTyphoidfever

qBrucellosis

q Bovinetuberculosis

qQfever

Steamsterilizer:babiesbottlessterilizer-sample

ChemicalMethods•.UseofDisinfectants/Antiseptics

eg.phenolics,chlorhexidine,alcohol,iodine,etc.

•Somestrongchemicalsubstancesmaybeusedtoachievesterilization(killspores)suchas:glutaraldehyde&ethyleneoxide

Strongchemicalsusedforheatsensitiveitemswhichareusedforsterilebodysites.

SterilizationbystrongChemicalsUsefulforheatsensitivematerialse.g.plasticsandlensedendoscopes).

1.EthyleneOxideChamber

EthyleneoxidealkylatesDNAmoleculesandthereby

inactivatesmicroorganisms.

Temperature:55-60°C andexposureperiod4-6hours.

2.ActivatedalkalineGluteraldehyde 2%

Immerseiteminsolutionforabout20minutes.

IfMycobacterium tuberculosis or sporespresentthenimmersionperiodis2-3hours.

3.Otheruses:Hypochlorite atcertainconcentrationsusedfordrinkingwatersupply,housecleaningandswimmingpools.

Factorsinfluencingactivityofdisinfectants1.Activitydirectlyproportionalto temperature.

2.Directlyproportionaltoconcentration anoptimumconcentration.Afterthislevelnoadvantageinfurtherincreasesinconcentration.

Factorsinfluencingactivityofdisinfectants3.Maybeinactivatedby◦ Dirt◦ Organicmatter:Proteins,Pus,Blood,MucusandFeces.◦ Nonorganic:Cork,HardwaterandSomeplastics.

4.Time:Disinfectantsneedtimetowork.

5.RangeofAction:Disinfectantsarenotequallyeffectiveagainstthewholespectrumofmicrobes.

e.g.Chlorhexidine lessactiveagainstGramnegativebacteriathanGrampositivecocci.

Hypochlorite andGluteraldehyde aremoreactiveagainsthepatitisvirusesthanmostotherdisinfectants.

CorrosiveAction

Inactivated byTB

Activity againstGPCAntiseptics

/DisinfectantsSoapProteinSporesGNB

+_++_++++PhenolicsSudol

__+__++++Izal

to ++_++_++++SolublePhenolic*e.g. Clearsol

(buffered + ++ orSolution)

_+++++++++Chlorinecompound

__+++(Slow)

++++Iodophor

_____+++Chlorhexidine(Hibitane)

__+++_++++70°Alcohol

++_+++++(slow)

++++Formaldehyde

+_+++++++++Glutaraldehyde(Cidex)

HospitaldisinfectionmethodsArticle DisinfectantFloors,wallsPhenolics fluids1-2%

SurfacestablesHypochlorite,Alcohol

Skin

Surgeons’ handsChlorhexidine,Iodine

alcohol

Patientskin70%Alcohol,Iodine

Endoscopes Gluteraldehyde 2%

(Cidex),subatmospheric

steam

Thermometers 70%Alcohol

ImportanttorememberAnyinstrumentoritemusedforsterilebodysiteshouldbesterile.Anyinstrumentoritemusedfornon-sterilebodysitecanbedisinfected.

ReferencebookSherris Medical Microbiology, an Introduction to Infectious Diseases.

Latest edition, Kenneth Ryan and George Ray.

Publisher : McGraw Hill .