Chapter 11物理和化学因素对微生物的控制

ChapterOverview•Thecontrolofmicrobesintheenvironmentisaconstantconcernofhealthcareandindustrysincemicrobesarethecauseofinfectionandfoodspoilage(破坏),amongotherundesirableevents.•Antimicrobialcontrolisaccomplishedusingbothphysicaltechniqueandchemicalagentstodestroy,remove,orreducemicrobesinagivenarea.••Manyfactorsmustbecontemplated（关注）whenchoosinganantimicrobialtechnique,includingthematerialbeingtreated,thetypeofmicrobesinvolved,themicrobialload,andthetimeavailablefortreatment.•Antimicrobialagentsdamagemicrobesbydisruptingthestructureofthecellwallorcellmembrane,preventingsynthesisofnucleicacids（DNAandRNA）,oralteringthefunctionofcellularproteins.Microbicidalagentskillmicrobesbyinflictingnonreversible（不可逆的）damagetothecell.microbistaticagentstemporarilyinhibitthereproductionofmicrobesbutdonotinflictirreversibledamage.Mechanicalantimicrobialagentsphysicallyremovemicrobesfrommaterialsbutdonotnecessarilykillorinhibitthem.•Heatisthemostphysicalagentinmicrobialcontrolandcanbedeliveredinbothmoist(steamsterilization,pasteurization)anddryforms.•Radiationexposesmaterialtohighenergywavesthatcanenteranddamagemicrobes.Examplesareionizingandultravioletradiation.•Chemicalantimicrobialareavailableforeverylevelofmicrobialtreatment,fromlow-leveldisinfectantstohigh-levelsterilants.Antimicrobialchemicalincludehalogens,alcohols,phenolics,peroxides,heavymetals,detergents,andaldehydes.ControllingMicroorganisms•Controllingourdegreeofexposuretopotentiallyharmfulmicrobesisamonumental（非常的）concerninourlives,andithasalongandeventful（重大的）history.GENERALCONSIDERATIONSINMICROBIALCONTROL•Themethodsofmicrobialcontrolbelongtothegeneralcategoryofdecontamination（净化）procedures,inthattheydestroyorremovecontaminants.Mostdecontaminationmethodsemployeitherphysicalagents,suchasheatorradiation,orchemicalagentssuchasdisinfectantsandantiseptics（无菌的）.RELATIVERESISTANCEOFMICROBIALFORMS•Theprimarytargetsofmicrobialcontrolaremicroorganismscapableofcausinginfectionorspoilagethatareconstantlypresentintheexternalenvironmentandonthehumanbody.•Thistargetedpopulationisrarelysimpleoruniform;infact,itoftencontainsmixturesofmicrobeswithextremedifferenceinresistanceandharmfulness.•Contaminantsthatcanhavefar-reachingeffectsifnotadequatelycontrolledincludebacterialvegetativecellsandendospores,fungalhyphaeandspores,yeasts,protozoantrophozoites（滋养体）andcysts,worms,insectsandtheireggs,andviruses.Thisschemecomparesthegeneralresistancetheseformshavetophysicalandchemicalmethodsofcontrol:•Highestresistance•Bacterialendospores•Moderateresistance•Protozoancysts:somefungalsexualspores(zygospores接合孢子);someviruses.Ingeneral,nakedvirusesaremoreresistantthanenvelopedforms.•Leastresistance•Mostbacterialvegetativecells;fungalsporesandhyphae;envelopedviruses;yeasts;andprotozoantrophozoites.•Actualcomparativefiguresontherequirementsfordestroyingvariousgroupsofmicroorganismsareshownintable11.1TERMINOLOGY（术语）ANDMETHODSOFMICROBIALCONTROL•Throughtheyears,agrowingterminologyhasemergedfordescribinganddefiningmeasuresthatcontrolmicrobes.Tocomplicatematters,theeverydayuseofsomeofthesetermscanattimesbevagueandinexact.•Sterilization•Sterilizationisaprocessthatdestroysorremovesallviablemicroorganisms,includingviruses.Anymaterialthathasbeensubjectedtothisprocessissaidtobesterile.•Sterilizedproductsareessentialtohumanwell-being.Althoughmoststerilizationisperformedwithaphysicalagentsuchasheat,afewchemicalcalledsterilantscanbeclassifiedassterilizingagentsbecauseoftheirabilitytodestroyspores.•Attimes,sterilizationisneitherpracticablenornecessary,andonlycertaingroupsofmicrobesneedtobecontrolled.KeepinmindthatthedestructionofsporesisnotalwaysanecessitySterilizationHighTemperature（高温）UltravioletRays（紫外线）Hightemperaturecanmakeprotein、nucleicacid（核酸）、lipid（脂类）andothermacromolecules（生物大分子）todegraded（降解）、denaturalized（变性）anddestoryed.HighTemperatureHighTemperatureSterilizationDryHeatSterilization(干热空气灭菌法)MoistHeatSterilization(湿热空气灭菌法)FlameBurn（灼烧）HighTemperatueinOven（干热空气灭菌）NormalPressureHighPressurePasteurization(巴氏消毒法)Boiling（煮沸法）Tyndallization(间歇灭菌法)ContinuousPressureSterilization（连续高压灭菌）NormalPressureHighPressureNormalPressureSterilization（常压灭菌）FlameBurnOese(接种环)HighTemperatueinOvenOven（烘箱）CultureDish(培养皿)Method:160°Cfor2Hours.Pasteurization(巴氏消毒法)LouisPasteur(December27,1822–September28,1895)LouisPasteurwasaFrenchchemistandmicrobiologistbestknownforhisremarkablebreakthroughsinthecausesandpreventionofdisease.ConceptionofPasteurizationTheheatingofeveryparticleofmilkormilkproducttoaspecifictemperatureforaspecified（特定的）periodoftime.Aim:Heatingliquidsforthepurposeofdestroyingbacteria,protozoa（原生动物）,molds（霉菌）,andyeasts（酵母）.PasteurizationSystem巴氏消毒系统TheStructureofPasteurizerPasteurizationHIghTemperature/ShortTime(超高温瞬时灭菌HTST)LowTemperatureHoldingMethod(低温维持法LTH)63°Cfor30minutes138°CforseveralsecondsBoiling（煮沸法）Method:100°CforseveralminutesTyndallization间歇灭菌法Conception:Tyndallizationisamethodusedtodestroybacteriaandendospores（芽孢）whichrequiresnopressurecooker.1.80-100°Cfor15-60Mintues2.37°CforOvernightInducingSpore(