1. Sterilization and Disinfection
Rashad Shawgi Babiker
M.Sc (Microbiology) (UMST)
M.Sc. Stud. (Immunology )
Institute of Tropical Medicine.(SAS)

2. OUTLINES Bactericidal vs Bacteriostatic Sterilization vs Disinfection
Sepsis, Aseptic and Antisepsis

3. Sterilization and disinfection

4. Sterilization
a process whereby an item is freed of any living micro-organism or their dormant stage.

5. Sterility
total absence of viable microorganisms as assessed by no growth on any medium

6. Disinfection removal or killing of disease-causing microorganisms
Used to reduce number of viable microorganism .

7. Definitions Sepsis : infection Aseptic : without infection
Antisepsis : any procedure that inhibits the growth and multiplication of microorganisms on body surface such as the skin

9. Physical Sterilization sterilization by heat
Thermal death point :- This the lowest temperature above the optimum temperature , at which the growth of microorganism stops, and death occurs in a given time. Thermal death time:- This the shortest time at which growth of microorganism stops & death occurs at a certain temperature .

10. DRY HEAT
Incineration.
Red heat (Bunsen flame) includes sterilization of wires ,forceps , needles etc
hot-air ovens are usually held at 160–180°C for 2 hours. {plastics}.??

11. Pasteurization < 100 °C
Louis Pasture's discovery.
Milk at 65 for 30 min

12. Boiling 100 °C
30 minutes of boiling kills microbial pathogens and vegetative forms of bacteria but may not kill bacterial endospores
Tendelization !!

13. Autoclaving > 100 °C
Moist heat (autoclaving at 121°C for 15 minutes at a steam pressure of 15 pounds per square inch kills microorganisms, including endospores)

14. Control
Although measurements of the temperature are important, biological controls offer a direct measure of the sterilising power of the system.
For this purpose suspensions of bacterial spores (commonly Bacillus stereothermophilus spores) as well as control strips.

15. IRRADIATION Infrared radiation: temperature of objects rapidly
Ultraviolet radiation 210–330 nm (blocks DNA replication-dimer formation-)
Ionising radiation: X-ray and g-rays (high energy and penetration)

16. FILTRATION
Temperature-sensitive substances such as carbohydrates and amino acids that will be destroyed by heat sterilisation need to be sterilised by filtration.
The pore size (0.2 μm) will prevent bacteria passing through the filter.

17. Chemicals Alcohols Phenols is used as a disinfectant standard.
Chlorhexidine : useful topical disinfectant.
Iodine : can cause hypersensitivity reactions.
Chlorine : inactivates bacteria and most viruses
Formaldehyde
Ethylene oxide ((CH2)2O) : is an alkylating agent (heat-sensitive hospital instruments.)

18. Physical methods:- Method Temperature Effectiveness Use Boiling 100o
30 minutes of boiling kills microbial pathogens and vegetative forms of bacteria but may not kill bacterial endospores
Syringes
Intermittent boiling
Three 30-minute intervals of boiling, followed by periods of cooling kills bacterial endospores
To kills bacterial endospores
Autoclave and pressure cooker (steam under pressure)
121o/15 minutes at 15# pressure
kills all forms of life including bacterial endospores. The substance being sterilized must be maintained at the effective T for the full time
Cultures, lab glassware, pipettes, syringes, or other small items

19. Physical methods:- Method Acceptable for... How? Special Precautions
Comments
Ionizing Radiation
Prepackaged medical devices, including operating room supplies such as syringes and catheters
None
Not a practical tool for the laboratory
Ultraviolet Radiation
Within BSCs to maintain low levels of contamination
Installation of a lamp in BSC
Shadows and dust on the lamps can reduce effectiveness
Has low penetrating power
Limited usefulness
Among least effective methods
Not practical for liquids
Filtration
Removal of bacteria, yeast, and molds from biological and pharmaceutical solutions
Common pore sizes are 0.22 µm, 0.45 µm, and 0.8 µm

20. Chemical methods:- Method Acceptable for... How? Special Precautions
Comments
Glutaraldhyde
Glassware and instruments; items that can be submerged and soaked in a covered container; considered a sporacidal
2% concentration for minutes; rinse with sterile water to remove residuals
Sensitivity problems have developed in workers using it at high levels
Phenolic Compounds
General use on walls, floors, bench tops; bacteria; fungi; and lipid-containing viruses
0.2-3% concentration for minutes
Can cause depigmentation, occupational leukoderma, idiopathic neonatal hyperbilirubinema
Not active against spores or non-lipid viruses