How is the Autoclave Temperature Significant in Sterilization

by dewi susanti

Modern society is so conscious about germs and the need to minimize infections. The autoclave is a device that is used chiefly to sterilize contaminated or potentially infectious appliances, equipment and wares.

The autoclave temperature and pressure is sufficient for a number of sterilization applications in which microorganisms are to be killed or inactivated. For this reason, the autoclave is so popular in medicine, microbiology, veterinary science, dentistry, mycology, tattooing, fabrication of prosthetics and body piercing circles, where the need to prevent infections through sterilization is obligatory.

So how important is the autoclave temperature?


Autoclave temperature

Autoclave temperature

Potentially infectious organisms thrive well at specific ranges of temperatures. Usually, the optimum temperature at which most infectious organisms would thrive and multiply quickly is around 35-37 0C, which is just about the normal temperature of the human body. However, some infectious agents can thrive well at temperatures that are well beyond the human body temperature.

In order to protect themselves from being destroyed by extreme temperature, some bacteria turn into the highly resistant forms called spores. In order to kill or deactivate these resistant forms of micro-organisms, they have to be exposed to extremely high temperatures. The autoclave temperature of 121 0C is effective in eliminating most strains of bacteria and other micro-organisms.

Secondly, different items can withstand different ranges of temperature. Some are heat-resistant while others are heat-labile. The ordinary autoclave uses superheated water and steam to sterilize items, but quite a number of items cannot stand these extreme hot air oven temperatures. To save such heat-labile items as gloves, culture media, rubber material and gowns from being destroyed, they are sterilized without using pressure vessels.

Heat-labile products (like plastics) must never be autoclaved as they can melt away while products that can be damaged by steam, such as paper, should also not be autoclaved. Conversely, high autoclave temperature and pressure is used in rubber vulcanization and composite curing to ensure that desirable physical properties are attained repeatedly. Higher temperatures are used in the large autoclaves that are preferred by spar-makers and the aerospace industry.

While the use of autoclaves in the sterilization of various media, such as surgical instruments, medical waste, ordinary waste, equipment and laboratory glassware is on the rise, there is growing demand that the autoclave temperature is sufficient for the suspected micro-organisms that could be in the items to be autoclaved.

One factor that may reduce the degree of sterilization at any particular autoclaving temperature is trapped air. For instance, at an autoclave temperature of 134 0C, steam will attain the same degree of sterilization in three minutes as that which hot air will only attain at 160 0C for 2 hours.

Hot air is not a good sterilization medium and should therefore be removed before the autoclave is activated. Moreover, the items being autoclaved must usually be separated so that steam can penetrate fully and evenly into the load.

Sterility is achieved when sterilization is done at a specific autoclave temperature for the right duration of time. To confirm this, various biological, chemical and physical indicators are usually applied to the autoclaved media. Chemical indicators will typically show specific color changes when the right conditions and full processing has been reached.

Biological indicators are primarily spore-based, supplied with the heat-resistant Geobacillus stearothermophilus bacteria. The germination of the bacterial spores after any sterilization event indicates that the process did not meet the correct autoclave temperature. Physical indicators are usually in the form of alloys designed to melt at specific temperatures. If after autoclaving the alloys have not melted then sterility has not been achieved.

In conclusion, autoclaving relies greatly on the specific temperature used and for how long the organisms are exposed to the heat. Before using an autoclave, one should know whether the media to sterilize is heat-labile or resistant, the correct autoclave temperature for the media, the suspected organisms and how long they should be exposed to heat in order to be inactivated or killed, and the right autoclaving procedure. It is a question of mastering the basics before the process. Do you want to know more about autoclaves and sterilization? Follow the links for more information.

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