IA. General microbiology | 5. Sterilization Flashcards
I. Sterilization
1. What is sterilization?
- killing procedure of any kind of germs ……..
- inactivation (killing) of all forms of microbial life (pathogenic microbes and spores)
I. Sterilization
2. What is sterile?
Sterile: an object that is free of all living organisms
I. Sterilization
3. How can sterile be achieved?
Can be achieved via application of heat, chemicals, iradiation, high pressure and filtration
I. Sterilization
4. What is the aim of sterilization?
Complete removal or destruction of all forms of microbial life including bacterial spores
I. Sterilization
5A. What is decimal time (D)?
- Decimal time (D): time needed to reduce the initial number (N0) to one tenth of its original value
- Number of microorganisms (N) after sterilization is given by:
I. Sterilization
5B. What are the features of D?
D varies with temperature, type of organism, water activity, pH, etc.
■ D becomes considerably shorter with increased temperature → high temperature will reduce the N0 faster than low temperature.
I. Sterilization
6. What are the 5 applications of sterilization?
○ Sterilization of medical instrumentations
○ Annihilation of infectious waste
○ Sterilisation of injectable medications
○ Skin disinfection
○ Food safety
II. Methods of Sterilization
1. Classification of methods of sterilization
II. Methods of Sterilization
2. Classification of physical methods
II. Methods of Sterilization
3. Classification of chemical methods
II. Methods of Sterilization
4. Classification of mechanical method
II. Methods of Sterilization - Physical method (Heat)
1. What are the features of flaming (dry heat) method?
○ Instruments are held in flame until they become red hot
○ Incinerating biological waste from hospitals and laboratories
○ Use: inoculation loop, inoculation needle, scalpels, mouth of test
tube, top of forceps
II. Methods of Sterilization - Physical method (Heat)
2. What are the features of hot air oven (dry heat) method?
Hot air oven (dry heat) – most widely used method
○ Heating at atmospheric pressure and often use a fan to obtain uniform temperature by circulation
○ 1hr→ 180°C ;2hr →160°C; 3hrs→140°C
○ Use: laboratory glassware, ceramics, surgical instruments
without sharp edges, powders
tube, top of forceps
II. Methods of Sterilization - Physical method (Heat)
3A. What are the features of utoclaving (moist heat) or steam sterilizer?
- Insulated pressure chamber in which saturated steam is used to elevate the temperature
- Denaturation and coagulation of microbial protein occur during exposure to the high temperature of the steam
- 121°C at +1atm overpressure for 20-30mins
- 134°C at +2atm overpressure for 10mins
II. Methods of Sterilization - Physical method (Heat)
3B. Why is autoclaving (moist heat) or steam sterilizer more effective than DRY HEAT?
- More rapid, even penetration
- Better bactericidal/virucidal effect
- Short efficient cycle time
II. Methods of Sterilization - Physical method (Heat)
3C. What is the use of autoclaving (moist heat) or steam sterilizer?
Microbiological media, solutions, glasswate, surgical instruments, cotton items, items made of autoclavable rubber, swabs, tissue paper
II. Methods of Sterilization - Physical method (Heat)
3D. Give steps of Autoclave sterilization methods to destroy prions (protein only)?
- 1N NaOH 2hrs or 2N NaOH 1hrs
- +2atm overpressure, 134°C, 1hrs
- Repeat whole process
II. Methods of Sterilization - Physical method - Radiation
5A. What are the 2 types of radiation method?
- UV light
- Gamma sterilization
II. Methods of Sterilization - Physical method - Radiation
5B. What are the features of “UV Light” method?
- Germicidal lamps: short distance → surface, air, biological safety
- Cabinets, laminar flow cabinet → totally germfree
- DNA mutates and breaks down → damage the structure and function of nucleic acid → cell death
- Can cause damage to human cells
II. Methods of Sterilization - Physical method - Radiation
5C1. What are the features of “Gamma sterilization” method?
- Coblat 60 radiation to kill microorganisms
- Produce electron disruptions (ionization) in any material that it encounters
- Living organism – disruptions result in damage to the DNA and other cellular structures – could cause death in organisms
- Can damage human cells – risk of cancer
- Use: single use, individually packaged, heat sensitive instruments (plastics, swabs catheters, infusion set, glove syringe
II. Methods of Sterilization - Physical method - Radiation
5C2. What is the use of “Gamma sterilization” method?
Use: single use, individually packaged, heat sensitive instruments (plastics, swabs catheters, infusion set, glove syringe
II. Methods of Sterilization - Chemical method
6B. What are the features of gas sterilization?
- Ethylene oxide, β-propiolactone, ortho-phthalaldehyde (OPA),formaldehyde
- Highly penetrative, non-corrosive agents
- Against: bacteria, spores and viruses
- Destroys microorganism by alkylation; and causes denaturation of nucleic acid
- Use: single use, heat-sensitive, medical devices (prosthetic heart valves and plastic catheters and textiles)
II. Methods of Sterilization - Chemical method
6C. What are the features of Plasma sterilization?
- Low-temp (~46°C), low humidity sterilization with plasma state hydrogen peroxide created using an electromagnetic field
- Gas like plasma – cloud of ions, electrons, neutral atomic particles – created free radicals and biologically active particles destroy microorganisms.
- Electromagnetic field is turned off – hydrogen peroxide decays to water and oxygen
- Use: metallic, non-metallic, wet/heat - sensitive instruments
- At the end of the procedure there will be H2O, O2 & non toxic products
