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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.
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
ChemicalMethods•.UseofDisinfectants/Antiseptics
eg.phenolics,chlorhexidine,alcohol,iodine,etc.
•Somestrongchemicalsubstancesmaybeusedtoachievesterilization(killspores)suchas:glutaraldehydeðyleneoxide
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.