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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

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sterilization and disinfection
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 endospores

Bacteriostasis

to inhibit the growth of bacteria

slide3
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
METHODS
  • Physical methods of disinfection and sterilization
  • Chemical methods of disinfection and sterilization
section 2 physical controls on microoganisms for disinfections and sterilization

Section 2 Physical controls on microoganisms for disinfections and sterilization

including
Including:
  • Heat
  • Cold
  • Drying
  • Radiation
  • Filtration
  • Osmotic strength
dry heat
Dry heat

Hot air sterilization

  • Flaming

Incineration

Hot air sterilization

Conditions

160-170℃, 1-2hrs

Significance & applications

glassware, metal objects

moist heat
Moist heat

Moist heat

Boiling water

Autoclaving

Pasteurization

slide9

burning method(incineration)

flowing steam disinfection

boiling water disinfection

hot air drying method(烤箱)

moist heat10
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
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)
slide12
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
slide13
Autoclaving

Conditions: When pressure is 102.97~137.30kpa, the temperature in the autoclave can reach 121ºc, 15~20 minutes is enough for sterilization

slide14
Significance:

kills both spores and vegetative microorganisms

the most common and effective method of sterilization

Application:

sterilizes materials not damaged by heat and moisture

comparison
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
Radiation
  • Ultraviolet radiation

The most effective wavelengths: 250-260nm

Mechanism: destroy DNA by forming thymine dimers

Characteristics:

poor penetrating power

damage of the eyes and the skin

Applications:

Air disinfections

Surface disinfection

filtration
Filtration
  • Mechanism

mechanically removes microorganisms

  • Application

sterilize materials likely to be damaged by heat

chemical antimicrobial methods
Chemical antimicrobial methods
  • Mechanisms

Injury of cell membranes

Inactivation of proteins (e.g., enzymes )

Damage of genetic materials

chemical antimicrobial methods20
Chemical antimicrobial methods
  • Common chemical agents

Phenol

Soaps and detergents

Alcohols: 70-75%

Heavy metals: Silver nitrate (1%)

Chlorine

Iodine

Aldehydes: 37% Formalin

Dyes: crystal violet

factors influencing antimicrobial activity
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
Biological methods
  • Antibiotic
  • Bacteriocin
  • Bacteriophage
some question
Question:

What is the Mechanisms of the Chemical antimicrobial methods

Some question

TERMS EXPLAINATION:

Sterilization 、 disinfection、Bacteriostasis、Antisepsis

Asepsis、 Aseptic techniques