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Disinfection and Sterilization

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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Disinfection and Sterilization

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  1. Disinfection and Sterilization

  2. 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

  3. 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.

  4. METHODS • Physical methods of disinfection and sterilization • Chemical methods of disinfection and sterilization

  5. Section 2 Physical controls on microoganisms for disinfections and sterilization

  6. Including: • Heat • Cold • Drying • Radiation • Filtration • Osmotic strength

  7. Dry heat Hot air sterilization • Flaming Incineration Hot air sterilization Conditions 160-170℃, 1-2hrs Significance & applications glassware, metal objects

  8. Moist heat Moist heat Boiling water Autoclaving Pasteurization

  9. burning method(incineration) flowing steam disinfection boiling water disinfection hot air drying method(烤箱)

  10. 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

  11. 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)

  12. 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

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

  14. Significance: kills both spores and vegetative microorganisms the most common and effective method of sterilization Application: sterilizes materials not damaged by heat and moisture

  15. 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.

  16. 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

  17. Filtration • Mechanism mechanically removes microorganisms • Application sterilize materials likely to be damaged by heat

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  19. Chemical antimicrobial methods • Mechanisms Injury of cell membranes Inactivation of proteins (e.g., enzymes ) Damage of genetic materials

  20. 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

  21. The effects types of disinfectants

  22. 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

  23. Biological methods • Antibiotic • Bacteriocin • Bacteriophage

  24. Question: What is the Mechanisms of the Chemical antimicrobial methods Some question TERMS EXPLAINATION: Sterilization 、 disinfection、Bacteriostasis、Antisepsis Asepsis、 Aseptic techniques

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