1. Sterilization &Disinfection

2. Main contents Some concepts Physical sterilization and disinfection
Chemical sterilization and disinfection(self-study)
Factors affecting disinfectant potency(self-study)

3. Control of microorganisms is essential in order to prevent the transmission of diseases and infection, stop decomposition and spoilage,and prevent unwanted microbial contamination.

4. Definitions Sterilization:
The process of killing or removing all living microorganisms including pathogenic/non-pathogenic microorganisms, vegetative forms/spores.
The standard of sterilization is to kill spores.

5. Disinfection: The process of killing or removing pathogenic microorganisms. Bacterial spores and other relatively resistant organisms may remain viable.
Disinfectants:
Chemical agents for disinfection

6. Bacteriostatics: the chemical agents
Bacteriostasis: is a process that growth of bacteria is inhibited.
Bacteriostatics: the chemical agents
used for bacteriostasis, usually in vivo
e.g., antibiotics.
Antisepsis: the process of inhibiting bacterial growth and reproduction ,
Antiseptics: Chemical agents for antisepsis ,used in vitro

7. Prevent the microbes to enter into human body or other thing.
Asepsis: a state of sterility (no living microorganisms) the result of sterilization
Aseptic techniques:
Prevent the microbes
to enter into human
body or other thing.

8. Physical sterilization and disinfection
Heat
Radiation
Filtration
Ultrosonic
Dessication and freezing

9. Heat
Dry heat
Incineration
Flaming
Hot-air sterilization

10. Incineration: destroy disposable or expendable material by burning
Flaming: inoculating loops and needles
and the neck of test-tubes

11. Dry heat Hot-air sterilization Conditions 160-170℃, 2hrs
Significance & applications
glassware, porcelains, metal objects

12. Hot-air sterilizer

13. Moist heat
Boiling water
Steam sterilization at atmospheric pressure
Pasteurization
autoclaving

14. Moist heat Boiling water Bacteria vegetative cell---5min
Spore can survive hours of boiling
Steam sterilization at atmospheric pressure
Bacteria vegetative cell min
Spore is hard to kill

15. 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.

16. Significance: kills vegetative pathogens , destroy Mycobacterium
Conditions: 62℃, 30min or 71.7℃, 15-30sec
Significance: kills vegetative
pathogens , destroy Mycobacterium
tuberculosis and Brucella
Applications: milk, beer, wine

17. Father of Microbiology

18. Moist heat
Autoclaving
Conditions: kpa, 121.3℃, minutes
Significance: kills both spores and vegetative
microbes. The most common and effective
method of sterilization
Application: sterilizes materials not damaged by
heat and moisture

19. Autoclave

20. materials prepared for autoclave

21. Comparison Moist heat is generally more effective than dry heat
Reasons
- Steam is more easily to denature proteins.
- Steam penetrates more easily.
- Steam could send out potential heat.

22. Radiation Ultraviolet radiation
An electromagnetic wave at wave length nm
The most effective wavelengths: nm
Mechanism: destroy bacteria by forming
thymine dimers
Characteristics:
poor penetration and damage of the eyes and
the skin
Applications:
Air disinfections
Surface disinfection

23. Ionizing radiation
X-rays,γ-rays have more energy and penetrating power than ultraviolet radiation
Produce radicals destroying DNA
Pharmaceuticals, disposable medical supplies, food

25. Filtration Mechanism 0.025-0.45μm(NC filter)
mechanically removes microorganisms
μm(NC filter)
0.22 μm is commonly used to remove bacteria
Virus,mycoplasmas,L-form bacteria

26. Application
sterilize materials likely to be damaged by heat, such as animal sera,enzyme solutions,vitamin solutions,antibiotics solutions,vaccines

27. Other methods Ultrasonic Sound having frequency higher than 20kHz
Commonly used in disrupting cells
Disease diagnosis in clinical practice
Of no practical value in sterilizaition and disinfection

28. Dessication and low temperature
Lyophilization ---- commonly used method of culture preservation

29. Chemical antimicrobial methods
Mechanisms of action
-- Destroy cell membranes;
e.g., surfactants/detergents -- dissolve lipids
-- Denature bacterial proteins (e.g. enzymes );
e.g., alcohol-- Interfere bacterial metabolism
-- Damage genetic materials (DNA, RNA);
e.g., formaldehyde

30. Chemical antimicrobial methods
Commonly used chemical agents
Phenol
Soaps and detergents
Alcohols: 70-75%(medical use)
Heavy metals: Silver nitrate (1%)
Chlorine
Iodine
Aldehydes: 37%, Formalin
Dyes: crystal violet

31. This chapter focuses on
Definitions
Disinfection, Sterilization, Asepsis, Aseptic technique;
Bacteriostasis
Pasteurization
Questions
What agents contribute to the control of microbes?
How are dry heat and moist heat used to control microorganisms?
Why is moist heat more effective than dry heat?
What is the mechanism of UV light’s killing bacteria?
What factors influence the effectiveness of antimicrobial agents?