Post on 18-Dec-2015
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Disinfection and Sterilization
Sterilization and disinfection
Disinfection The process that reduces the number of pathogenic
microorganisms. Bacterial spores and other relatively resistant organisms may remain viable.
Sterilization a treatment that destroys all microbial life,
including vegetative form and endosporesBacteriostasis to inhibit the growth of bacteria
Antisepsis:A chemical agent safely used in or on living tissue to destroy microorganisms.
Asepsis:a condition in which living microorganisms are absent.
Aseptic techniques: measures taken to ensure that living microorganisms are absent.
METHODS
Physical methods of disinfection and sterilization
Chemical methods of disinfection and sterilization
Section 2 Physical controls on microoganisms for disinfections and sterilization
Including:
Heat Cold Drying Radiation Filtration Osmotic strength
Dry heat
Hot air sterilization Flaming
Incineration
Hot air sterilization
Conditions
160-170℃, 1-2hrs Significance & applications
glassware, metal objects
Moist heat
Moist heat Boiling water
Autoclaving
Pasteurization
burning method(incineration) flowing steam disinfection
hot air drying method( 烤箱 )boiling water disinfection
Moist heat
Pasteurization
Definition: a process in which fluids are heated at temperatures below boiling point to kill pathogenic microorganisms in the vegetative state without altering the fluid’s palatability.
Conditions: 62℃, 30min or 71.7℃, 15sec
Significance: kills vegetative pathogens
Applications: milk, beer
Boiling:
100 at 1 atmospheric pressure℃ 5min killing most non-sporing bacteria For 1-2h will kill a few sporing microoganisms 2% sodium carbonate can enhance the
efficiency ,105 (the boiling point)℃
Steam sterillization with common pressure:It applies water vapor to disinfect 100 for 15℃ ~ 30min, not useful for spore
Fractional sterilization:It takes water vapor intermittently to sterilization at common pressure.it usually applies to medium containing sugar or milk,which cannot bear high temperature
Autoclaving Conditions: When pressure is 102.97~137.30kpa, the temperature in the autoclave can reach 121ºc, 15~20 minutes is enough for sterilization
Significance:
kills both spores and vegetative microorganismsthe most common and effective method of sterilizationApplication:
sterilizes materials not damaged by heat and moisture
Comparison
Moist heat is generally more effective than dry heat Reasons
Steam is more easily to inactivate proteins. (H bonds)
Steam penetrates more easily.
Steam has potent heat.
Radiation
Ultraviolet radiation The most effective wavelengths: 250-260nmMechanism: destroy DNA by forming thymine dimersCharacteristics:
poor penetrating power damage of the eyes and the skin
Applications: Air disinfectionsSurface disinfection
Filtration
Mechanism
mechanically removes microorganisms Application
sterilize materials likely to be damaged by heat
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滤菌过程
Chemical antimicrobial methods
Mechanisms Injury of cell membranes
Inactivation of proteins (e.g., enzymes )
Damage of genetic materials
Chemical antimicrobial methods Common chemical agents
PhenolSoaps and detergents Alcohols: 70-75%
Heavy metals: Silver nitrate (1%) Chlorine Iodine Aldehydes: 37% Formalin
Dyes: crystal violet
The effects types of disinfectants
Effects level Disinfectants examples
High level Ethylene oxide, peracetic acid ,kinds of aldehyde
Normal level Kinds of alcohol, kinds of iodine, chloric disinfectants
Low level Chlorhexidine, phenolic disinfectants
Factors influencing antimicrobial activity the concentration and kind of an agent used
the length of exposure to the agent
the temperature at which the agent is used
the number of microorganisms present
the kinds of microorganisms present
the nature of the material bearing the microorganism
Biological methods
Antibiotic
Bacteriocin
Bacteriophage
Some question
Question: What is the Mechanisms of the Chemical
antimicrobial methods
TERMS EXPLAINATION:Sterilization 、 disinfection 、 Bacteriostasis 、 AntisepsisAsepsis 、 Aseptic techniques