Physical methods of sterilization in microbiology. Physical methods of sterilization 2022-10-10
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In microbiology, sterilization refers to the process of eliminating or removing all forms of life, including bacteria, viruses, fungi, and spores. This is typically done to prevent contamination of materials or to ensure the safety of a product. There are various methods that can be used to sterilize materials, including physical methods such as heat, radiation, and filtration.
One of the most commonly used physical methods of sterilization is heat. Heat can be applied in various forms, including moist heat, dry heat, and steam. Moist heat, such as boiling or autoclaving, is the most effective method for sterilization because it can penetrate and denature proteins more effectively than dry heat. Autoclaving is a common method used in microbiology laboratories, where materials are placed in a special pressure cooker that uses steam to sterilize the materials.
Another physical method of sterilization is radiation, which includes ultraviolet (UV) light, gamma rays, and electron beam radiation. UV light is often used to sterilize air, water, and surfaces, as it is effective at killing bacteria and viruses. Gamma rays and electron beam radiation are more powerful forms of radiation that can be used to sterilize large volumes of materials, such as medical equipment and pharmaceuticals. However, these methods can be expensive and may not be suitable for all materials.
Filtration is another physical method of sterilization that is commonly used in the production of sterile liquids, such as intravenous fluids and injectables. Filtration involves passing the liquid through a special filter that removes bacteria and other contaminants. This method is particularly useful for liquids that cannot withstand high temperatures or radiation.
In conclusion, physical methods of sterilization, such as heat, radiation, and filtration, are important tools in microbiology for ensuring the safety and purity of materials. Each method has its own advantages and limitations, and the appropriate method should be chosen based on the material being sterilized and the required level of sterility.
13.2 Using Physical Methods to Control Microorganisms
Ionizing radiation is used to pasteurize or sterilize some products. The cylinders are graded as W dense , N normal , and V coarse , depending upon the sizes of the pores. These parameters are often used to describe sterilization procedures that use high heat, such as autoclaving. It has the disadvantages of being toxic and combustible and also requires the correct humidity. It has a discharge tap for air and steam at the upper side, a pressure gauge and a safety valve that can be set to blow off at any desired pressure. Although pasteurization inactivates most viruses and destroys the vegetative stages of 97—99% of bacteria and fungi, it does not kill endospores or thermoduricspecies mostly nonpathogenic lactobacilli, micrococci, and yeasts. Tightly packed load is heated rapidly and uniformly to the sterilising temperature for a shorter time, e.
Sterilisation by Moist Heat : Microorganisms can be killed by moist heat if they come in contact with water or steam; otherwise if they are protected from wetting, as by grease or in a relatively impervious container exposed at the same temperature; the moist heat will have the weaker effect than the dry heat. The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University. Another arrangement is the coupling of the filter to the flask through a ground-glass joint thus eliminating the use of a rubber stopper. The ideal minimum holding time is 15-30 minutes at 121°C 15 lb. Physical Methods of Sterilization Physical methods of sterilization include the following: a.
Sterilisation and Disinfection: Methods and Principles
This is a thermophilic bacterium with an optimum temperature of 55—60°C, and its spores require an exposure of 12 minutes at 121°C to be destroyed. Boiling for 10-30 minutes can kill most of the vegetative cells; however, many spores can withstand this temperature. Validation of autoclave has been described in detail in Practical Microbiology by Dubey and Maheshwari 2007. . Heated, circulated air transfers its heat to the materials inside the chamber.
Types of Sterilization Method Used in Microbiology
The third day re-ensures killing of all the spores by their germination to vegetative forms. Sterilization by Radiation : Radiations can be divided into two groups: electromagnetic waves and streams of particulate matter. More recently, however, attention has shifted to destruction of Coxiella burnetii, the agent of Q fever, because this organism has a higher resistance to heat. The finished cylinders are tested by connecting a tube to the nipple of the filter, submerging in water, and passing compressed air to the inside. The heat resistance of spores is diminished with increased acidity and alkalinity.
The contraction in volume causes immediate suction of more steam to the same site and this process continues till the temperature of the article is raised to the temperature of the steam. Berkefeld Filters : Kieselguhr is a deposit of fine, usually white siliceous powder composed chiefly or wholly of the remains of diatoms. The UV radiation causes protein denaturation and interferes with DNA replication of bacteria. The hot-air oven is electrically heated and is fitted with a fan to ensure adequate and eve n distribution of hot air in the chamber. Dry Heat Sterilization 3. Heat can kill microbes by altering their membranes and denaturing proteins. Early in the story the physician, Andrew Manson, begins his practice in a small coalmining town in Wales.
Since the penetration by the steam is hindered by the air, the air should not be trapped inside the autoclave; only pure steam is used. Apart from that, the materials containing the substances are also needed to be heat stable for proper sterilization. Moreover, a thermostat is present to monitor the temperature. Water of condensation from the steam is drained off through the jacket discharge channel which is thermostatically controlled. CBS Publications and Distribution.
Clogged filters may be cleaned in various ways but probably most conveniently by continuous suction of full-strength Clorox, or similar solution, for 5 to 15 min. Almost immediately, he encounters an epidemic of typhoid fever. Bacterial spores are the forms of bacteria which are inert. The liquid to be filtered is poured into the mantle, and the filtrate is collected in a graduated vessel, from which it may be withdrawn aseptically. Adjustment of pressure in a closed container can regulate the temperature of steam.
Lower temperatures and less time of exposure are therefore required than for dry heat. It was also called tyndallization after its developer, John Tyndall and intermittent sterilization because it was a stop-and-start operation. Physical Control by Other Methods: Filtration : Heat is valuable physical agent for controlling microorganisms but sometimes it is important to use. High intensity ultraviolet radiation is applied with great precautions to protect the skin, to the site of the operation to check the post operative sepsis. Direct sunlight has an active germicidal effect due to its content of ultraviolet and heat rays.
The number of microorganisms and spores; ADVERTISEMENTS: 3. However, most sonic machines are not reliable for regular use in disinfection or sterilization. The oven uses dry heat to sterilize articles at 50 to 300°C. For example, tubercle bacilli are destroyed in 30 minutes at 58°C, but in only 2 minutes at 65°C, and in a few seconds at 72°C. Each class is designed to provide a different level of protection for laboratory personnel and the environment; BSC II and III are also designed to protect the materials or devices in the cabinet.