Disinfection and Disinfection and Sterilization Sterilization ——For the course of Medical Microbiology for MBBS foreign students, Class 2006/2011, SYSU September 18, 2007 Mengfeng Li (黎黎黎) , M.D. Department of Microbiology, Zhongshan School of Medicine, SYSU, Guangzhou, China [email protected]Medical Microbiology Medical Microbiology
Medical Microbiology. Disinfection and Sterilization. —— For the course of Medical Microbiology for MBBS foreign students, Class 2006/2011, SYSU September 18, 2007 Mengfeng Li ( 黎孟枫) , M.D. Department of Microbiology, Zhongshan School of Medicine, SYSU, Guangzhou, China - PowerPoint PPT Presentation
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Disinfection and Disinfection and SterilizationSterilization
——For the course of Medical Microbiology for MBBS foreign students, Class 2006/2011, SYSU
September 18, 2007
Mengfeng Li (黎孟枫) , M.D. Department of Microbiology, Zhongshan School of
Early needs and success for disinfection Early needs and success for disinfection (Early 1800’s) —— a historic story(Early 1800’s) —— a historic story
• By mid-1800’s, almost half of post-operative patients died of sepsis (then By mid-1800’s, almost half of post-operative patients died of sepsis (then called “hospital disease”). called “hospital disease”). A common report by surgeons was: operation A common report by surgeons was: operation successful but patient diedsuccessful but patient died..
• A hypothesis: A hypothesis: ① ① exposing moist body tissue to oxygen exposing moist body tissue to oxygen sepsis;sepsis; ②② best best prevention: keeping air away from wounds by means of plasters, collodion or prevention: keeping air away from wounds by means of plasters, collodion or resins.resins.
• Having tried methods to encourage clean healing with no success, surgeon Having tried methods to encourage clean healing with no success, surgeon Joseph Lister discarded the concept of direct infection by bad air but Joseph Lister discarded the concept of direct infection by bad air but postulated that sepsis might be caused by a postulated that sepsis might be caused by a 'pollen-like dust'pollen-like dust‘, although he did ‘, although he did not know yet the “dust” was living microbes. not know yet the “dust” was living microbes.
• When Louis Pasteur suggested the presence of When Louis Pasteur suggested the presence of living organismsliving organisms in the air, in the air, Lister made the connection with wound sepsis: the Lister made the connection with wound sepsis: the microbesmicrobes in the air were in the air were likely causing the sepsis and should be destroyed before they entered the likely causing the sepsis and should be destroyed before they entered the wound.wound.
• Lister had previously heard that 'Lister had previously heard that 'carbolic acidcarbolic acid' was used to treat sewage, and ' was used to treat sewage, and that fields treated with the affluent were freed of a parasite causing disease in that fields treated with the affluent were freed of a parasite causing disease in cattle. He then cattle. He then began to clean wounds and dress them with carbolic acid..began to clean wounds and dress them with carbolic acid..
Joseph Lister operated with carbolic acid (石炭酸) spray
The milestone:
case of James Greenlees
-Aug. 12, 1865, James Greenlees, 11-year-old
-Struck by a horse-drown cart
-Compound fractures
-Taken to Royal Infirmary
-Under the care of Joseph Lister
Why disinfection and Why disinfection and sterilization?sterilization?
• Contagious diseasesContagious diseases• Hospital infection (e.g., OR, ID ward) or other Hospital infection (e.g., OR, ID ward) or other
opportunistic infection opportunistic infection • Lab contaminationLab contamination• Etc. Etc.
• Microbes:Microbes:- usually easy to grow in environment; usually easy to grow in environment; - but also can be inhibited or killed by certain but also can be inhibited or killed by certain
environmental (physical or chemical) environmental (physical or chemical) factors/conditions.factors/conditions.
• Process of reducing or Process of reducing or eliminating eliminating living pathogenic living pathogenic microorganismsmicroorganisms in or on in or on materials, so they are no longer materials, so they are no longer a health hazard.a health hazard.
For example: use of alcohol before For example: use of alcohol before drug injection.drug injection.
SterilizationSterilization (灭菌)(灭菌)• Process of destroying Process of destroying all all
microbialmicrobial forms. A sterile object forms. A sterile object is one free of all microbial forms, is one free of all microbial forms, including bacterial including bacterial sporesspores..
• More thorough than disinfectionMore thorough than disinfection
BacteriostasisBacteriostasis (抑菌)(抑菌)
• Process of inhibiting the growth Process of inhibiting the growth of microorganisms, of microorganisms, in vivoin vivo (mostly)(mostly) or or in vitroin vitro..
For example: bacteriostatic For example: bacteriostatic antibioticsantibiotics
Antisepsis Antisepsis (防腐)(防腐)• Process of inhibiting or preventing Process of inhibiting or preventing
growth of microbes, mostly growth of microbes, mostly in in vitrovitro and and not not bactericidal or bactericidal or sporicidal (sporicidal ( 杀芽胞的 杀芽胞的 ))
For example: use of chemical agents For example: use of chemical agents on skin, other living tissues or on skin, other living tissues or food/beverage.food/beverage.
AsepsisAsepsis (无菌)(无菌)
• A state where no living A state where no living microorganism exists. microorganism exists.
For example: OR (Operating Room)For example: OR (Operating Room)
Controlling Microorganisms Controlling Microorganisms with Physical Conditions with Physical Conditions
• High High TemperatureTemperature (heat) (heat)
• RadiationRadiation • Ultrasound Ultrasound
• FiltrationFiltration
• Low Temperature Low Temperature
• DesiccationDesiccation (干燥) (干燥)
High High Temperature Temperature ————Dry heat and Moist heat protein
denaturation and clotting; DNA strand breakdown
static action cidal action .
Dry heatDry heat :: protein oxidationprotein oxidation
• IncinerationIncineration (焚烧)(焚烧)– most thorough (>500℃)most thorough (>500℃)– disposals and corpesdisposals and corpes
• Hot air sterilization/BakingHot air sterilization/Baking (干烤)(干烤)– 160-170℃, 2h160-170℃, 2h– Glassware, china, syringes, needles, etcGlassware, china, syringes, needles, etc
• Infrared heat: similar to bakingInfrared heat: similar to baking
Moist heatMoist heat :: denaturing proteins and melt lipidsdenaturing proteins and melt lipids
• AutoclavingAutoclaving (高压蒸汽灭菌)(高压蒸汽灭菌)– Most commonly used and effectiveMost commonly used and effective– 121℃ (103121℃ (103.4kPa).4kPa),, 15- 15-20min20min– killing both vegetative organisms and killing both vegetative organisms and
endospores endospores
• BoilingBoiling– 100 ℃ (105℃ with 2% Na100 ℃ (105℃ with 2% Na22COCO22) , 15-20min) , 15-20min
– cidal for vegetative cells but not necessarily cidal for vegetative cells but not necessarily sporesspores
• Regular Steam (Arnold Sterilizer)Regular Steam (Arnold Sterilizer)– 100 ℃, 15-20min100 ℃, 15-20min– cidal for vegetative cells but not necessarily cidal for vegetative cells but not necessarily
sporesspores
• PasteurizationPasteurization (巴氏消毒法)(巴氏消毒法)– to kill pathogens in readily perishable to kill pathogens in readily perishable
• Fractional sterilizationFractional sterilization (间歇蒸气灭菌法)(间歇蒸气灭菌法)– alternating exposure and cooling time for a alternating exposure and cooling time for a
consecutive period:consecutive period:Steam heating (100 , 30 min)℃Steam heating (100 , 30 min)℃ 30 for ℃30 for ℃
endospores to endospores to germinategerminate 100 , 30 min to kill ℃100 , 30 min to kill ℃germinated endospores germinated endospores 30-37 overnight for ℃30-37 overnight for ℃remaining endospores to remaining endospores to germinategerminate 100 , 60 min to ℃100 , 60 min to ℃kill last remaining kill last remaining germinated endosporesgerminated endospores
– for sugar- or milk-containing culture media for sugar- or milk-containing culture media
• UltrasoundUltrasound– more effective for gram-negative bacteriamore effective for gram-negative bacteria– Lack of thoroughness Lack of thoroughness ———— survivors survivors
remainremain
• FiltrationFiltration – sterilize heat- or chemical-sensitive sterilize heat- or chemical-sensitive
solutionssolutions– not effective for virus, ricketia, not effective for virus, ricketia,
enzymesenzymes– not effective against endosporesnot effective against endospores– mainly for food reservation mainly for food reservation
• Low Temperature (-20℃ Low Temperature (-20℃ ~ ~ -70℃)-70℃)– inhibits microbial growth by slowing inhibits microbial growth by slowing
down microbial metabolismdown microbial metabolism– a special form: lyophalization (freeze-a special form: lyophalization (freeze-
drying), used for long-term (years) drying), used for long-term (years) reservation of bacteria stocks reservation of bacteria stocks • fast freezing + dryingfast freezing + drying
—— —— destroying cell membrane and cell wall, destroying cell membrane and cell wall, denaturing proteinsdenaturing proteins
•5-10ml/m5-10ml/m3 3 acetic acid evaporation acetic acid evaporation ———— air air disinfectiondisinfection
•quicklime [Ca(OH)quicklime [Ca(OH)22] ] ———— floor and excretion floor and excretion (feces, urine, sputum, pus) disinfection(feces, urine, sputum, pus) disinfection
Effectiveness of antimicrobial agents Effectiveness of antimicrobial agents are affected by ——are affected by ——
• The concentration/intensity and nature of The concentration/intensity and nature of the disinfectant; the disinfectant;
• Length of exposure;Length of exposure;• Species and number of the microbe(s); Species and number of the microbe(s); • Temperature and humidity;Temperature and humidity;• Acidity (pH);Acidity (pH);• Presence of organic substances;Presence of organic substances;• Presence of chemical antagonistsPresence of chemical antagonists• The nature of the material bearing the The nature of the material bearing the
microbesmicrobes
Summary 1. Application of Summary 1. Application of chemical disinfectants chemical disinfectants
High Killing all microbes including High Killing all microbes including glutaric dialdehydeglutaric dialdehyde (戊二醛),(戊二醛), endospores and TBendospores and TB formaldehyde peroxyacetic acidformaldehyde peroxyacetic acid(过氧乙(过氧乙 酸),酸), epoxy ethaneepoxy ethane (环氧乙烷)(环氧乙烷)
Medium Killing all non-spore microbesMedium Killing all non-spore microbes alcohol, chlorines, iodophoresalcohol, chlorines, iodophores including TBincluding TB
Low Killing vegetative bacteria Low Killing vegetative bacteria chlorhexidinechlorhexidine (洗必泰),(洗必泰), and lipophilic (enveloped) and lipophilic (enveloped) bromogeraminebromogeramine (新洁尔灭)(新洁尔灭) viruses, but resisted by viruses, but resisted by
endospores, TB and hydrophilic endospores, TB and hydrophilic (non-enveloped) viruses(non-enveloped) viruses
Summary 2. Potency levels of Summary 2. Potency levels of chemical disinfectantschemical disinfectants