Filteration Sterilization Method: - In bacteriological laboratary, it is occasionally neccessary to sterilize media or solutions, which would be broken down by heat. This is accomplished by the use of specially constructed filters which have small pores enough to hold back bacteria which allowing most or all of the other components of the solution to pass through.
Filters used in water purification or filtering procedures remove most of the bacteria but donot in the true sense produce sterile water.
Example: - Take a conical flask and funnel, and fixed the funel in conical flask. Put the filter paper on the funel and place the solution on the filter paper. Solution pass through the filter paper and microbes are retain on the paper.
Wednesday, May 5, 2010
Radiations Sterilization
Sterilization through radiation depends upon the wavelengh, intensity, and duration.
Ionising Raditions: - Those ionisations radiations which have less than 1 nm wavelength because of ionisation or to become ions.
For example: - Gamma rays when they react with DNA of microbes its chromosomes get mutate and proves to be lethal for the organisms. They have more penetration power. There generation is very difficult and costly.
Non-ionising Radiations: - These non-ionising raditions have wavelength ranging from 1 nm to 380 nm. They donot ionise the media for for example U.V rays. When U.V rays passes through the DNA of microbes, it breakes the bond between the T=A and causes the bond formation between T=T and A=A called thymine dimer.
Disadvantages: -
Ionising Raditions: - Those ionisations radiations which have less than 1 nm wavelength because of ionisation or to become ions.
For example: - Gamma rays when they react with DNA of microbes its chromosomes get mutate and proves to be lethal for the organisms. They have more penetration power. There generation is very difficult and costly.
Non-ionising Radiations: - These non-ionising raditions have wavelength ranging from 1 nm to 380 nm. They donot ionise the media for for example U.V rays. When U.V rays passes through the DNA of microbes, it breakes the bond between the T=A and causes the bond formation between T=T and A=A called thymine dimer.
Disadvantages: -
- Their penetration power is very low.
- They are harmful for human being.
Dry Heat Sterilization
This process is utilized to kill the microbes on the surface area. It is used to sterilize glassware, metal instruments and other heat stable solid materials which are not charged by high temperatures. Objects containing cotton, papers or plastic cannot be sterilized by this method because the high temperature will dull the cutting edge.
Approximately, one hour of heating up period is allowed for the entire load to reach the sterilization temperature.
Dry heat requires a much greater duration and intensity because heat conduction is less rapid in dry than the moist air. bacteria can survive in completely desiccated state and in this state the intrinsic heat resistance of vegetative bacterial cell is greatly increased, almost the level characteristics of the spores.
The death rate is much lower for dry cells than for fully hydrated ones.
There are two types of Dry heat sterilization.
Approximately, one hour of heating up period is allowed for the entire load to reach the sterilization temperature.
Dry heat requires a much greater duration and intensity because heat conduction is less rapid in dry than the moist air. bacteria can survive in completely desiccated state and in this state the intrinsic heat resistance of vegetative bacterial cell is greatly increased, almost the level characteristics of the spores.
The death rate is much lower for dry cells than for fully hydrated ones.
There are two types of Dry heat sterilization.
- Flame
- Incineration
Flame: - Any object such as a needle which can be heated to red heat will be rendered sterile. Red heat is positively assurance of sterility, of course such sterility will remain only so long as the cooled, sterile object is not contaminated.
Incineration: - (Oven based sterilization) It regulates the temperature 200*c for 2 hours. Medium in oven is air.
How to clean and dry glassware?
The glassware come in contact with, either directly or indirectly via medium, must be free of contaminating substances. Glassware often is contaminated or can easily become contaminated so it is easily important that all glassware should be handled with extreme care and its treatment needs be closely supervised.
Procedure:-
- First of all, labels and ink marking should be removing by wiping with acetone before washing and immediately rinse it.
- Clean the glassware with the help of detergent and then dipped into sulphuric acid solution containing potassium dichromate, which is effective for acid treatment of glassware.
- Glassware is placed in freshly prepared acid bath for at least one hour. Now the cleaning solution becomes dark brown, and then it should be discarded.
- Glassware removed from solution and placed in a suitable container distilled water and thoroughly rinsed.
- After rinsing, glassware should be dried thoroughly in the oven at 70*be covered and air-dried overnight.
- Wrap the glassware with the paper and fixed the autoclave tape. The color of the tape is white, acts as indicator to showed us the complete sterilization.
- Put the glassware in the autoclave bag. After 15 minutes, we can find the autoclave tape black, shows complete sterilization.
Differences between dry heat and moist heat
| Moist Heat | Dry Heat |
| 1. The moist heat have water and steam. | 1. No use of water and steam. |
| 2. Sterilization with coagulation of protein. | 2. Sterilization with oxidation. |
| 3. This process is under pressure. | 3. This process is on direct flame. |
| 4. Process takes less time. | 4. Process takes more time. |
| 5. Moist heat are Boiling & Autoclave. | 5. Dry heat are Flame & Incineration. |
Autoclaving
Autoclave: - The laboratory apparatus designed to use steam under regulated pressure is called autoclave. It is horizontal, rectangular, high pressure, high vac cum and high temperature steam sterilization. An autoclave is based upon downstream displacement principle where the steams enters in the chamber from the top, push the air down to remove it from the bottom of the sterilization.
It is commonly operated at steam pressure of 1.06kg/cm2 (151lbs in2) above the atmospheric pressure which corresponds to the temperature of 121*c with standard vac cum up to 26-28Hg mm. The medium exposed to temperature in excess of 121*c may not properly gel or may result in poor cell growth. Similarly the pressure should not exceed 20psi.
High temperature may lead to decomposition of carbohydrates and other components of the medium. The time of operation to achieved sterility depends upon the nature of the material being sterilized, the type of the container and the volume of the container.
For Example: - Utensils and rubber gloves in muslin wrappers will take 15 minutes for autoclave whereas Surgical packs in muslin wrappers, solution in Pyrex flasks, treatment trays will take 30 minutes.
The use of autoclave in the sterilization process has two advantages.
1. Reduction of formation of air pockets: If the autoclave at the pre vacuum stage (create vacuum, allow steam inside and so on again) the air removal and load is more effective because load gets gradually pre-heated. This reduces the time taken by load to attain the sterilization temperature.
2. Better drying sterilized product: After the sterilization cycle, when the vacuum is employed in the chamber for drying purposes, the it will reduce the drying time and it will give effective drying of fabrics and dressing. Because of the forceful evacuation of moisture trapped in these articles which increases the shelf life of fabrics items because if the sterilized fabrics are not dried and during the storage, if the vapour condense then they can get contaminated through air before use and microbiological growth will start in them making them unsterilized and thus useless.
It is commonly operated at steam pressure of 1.06kg/cm2 (151lbs in2) above the atmospheric pressure which corresponds to the temperature of 121*c with standard vac cum up to 26-28Hg mm. The medium exposed to temperature in excess of 121*c may not properly gel or may result in poor cell growth. Similarly the pressure should not exceed 20psi.
High temperature may lead to decomposition of carbohydrates and other components of the medium. The time of operation to achieved sterility depends upon the nature of the material being sterilized, the type of the container and the volume of the container.
For Example: - Utensils and rubber gloves in muslin wrappers will take 15 minutes for autoclave whereas Surgical packs in muslin wrappers, solution in Pyrex flasks, treatment trays will take 30 minutes.
The use of autoclave in the sterilization process has two advantages.
1. Reduction of formation of air pockets: If the autoclave at the pre vacuum stage (create vacuum, allow steam inside and so on again) the air removal and load is more effective because load gets gradually pre-heated. This reduces the time taken by load to attain the sterilization temperature.
2. Better drying sterilized product: After the sterilization cycle, when the vacuum is employed in the chamber for drying purposes, the it will reduce the drying time and it will give effective drying of fabrics and dressing. Because of the forceful evacuation of moisture trapped in these articles which increases the shelf life of fabrics items because if the sterilized fabrics are not dried and during the storage, if the vapour condense then they can get contaminated through air before use and microbiological growth will start in them making them unsterilized and thus useless.
Sterlization
Sterilization: - It is the process of inactivating or remove all the microbes and spores from the surface areas. Sterilization procedures provide the foundation for all bacteriological or sterile techniques and this process have common place in our everyday life.
For example: - In a hospital virtually everything must be sterilized.
The objectives of sterilization may be summarized as follows: -
1. To avoid the contamination of the product.
2. To permit only desired strain to be present in the vessel.
3. To ensure the safety of the product.
4. To prevent the deterioration of the products.
The sterilization may be achieved by heating, radiation and filtration process.
Pasteurization: - It is the process of mild heating of chemical of milk for removing the pathogens which are harmful for human beings.
For 72*c , 15 seconds sterilization.
For 140*c , less than 1 seconds sterilization.
Moist Heat: - There are two types of moist heat i.e. Boiling and Autoclaving.
1. Boiling: - Although effective in killing non sporing bacteria in a short-time is often relatively in effective against bacterial spores but it is generally safe because the instrument are clean before boiling and spores are rare under such circumstances. It is also used for minor rather than major surgical procedures.
For example: - Coagulation of protein
Take a beaker which is filled with water, boil the water at 100*c and water converts into the steam. When we applied the pressure the steam converts into the liquid water and the temperature increases. Now put the thing in a beaker at high temperature for sterilization.
For example: - In a hospital virtually everything must be sterilized.
The objectives of sterilization may be summarized as follows: -
1. To avoid the contamination of the product.
2. To permit only desired strain to be present in the vessel.
3. To ensure the safety of the product.
4. To prevent the deterioration of the products.
The sterilization may be achieved by heating, radiation and filtration process.
Pasteurization: - It is the process of mild heating of chemical of milk for removing the pathogens which are harmful for human beings.
For 72*c , 15 seconds sterilization.
For 140*c , less than 1 seconds sterilization.
Moist Heat: - There are two types of moist heat i.e. Boiling and Autoclaving.
1. Boiling: - Although effective in killing non sporing bacteria in a short-time is often relatively in effective against bacterial spores but it is generally safe because the instrument are clean before boiling and spores are rare under such circumstances. It is also used for minor rather than major surgical procedures.
For example: - Coagulation of protein
Take a beaker which is filled with water, boil the water at 100*c and water converts into the steam. When we applied the pressure the steam converts into the liquid water and the temperature increases. Now put the thing in a beaker at high temperature for sterilization.
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