Sterilization by Saturated Steam

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  • Topic: Autoclave, Bacteria, Sterilization
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  • Published : September 4, 2012
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Sterilization by Saturated Steam Mukul Bhatnagar: 21464987 Group Members: Chiew See Hau, Daryl Picard, Niamh Meagher, Musawwir Miriah

Introduction
Through the course of an entire day, an average human will come into contact with millions of different bacterial species. Just as human exposure to these bacterial species is high, the utensils we commonly use are subjected to a similar degree of exposure. Generally the temperature required to destroy many species of bacteria, fungi, viruses and yeasts is approximately 60C (van Doornmalen, 2008). However, some bacterial species contain endospores that are known to be thermoduric. When a bacteria is thermoduric, it is able to withstand prolonged exposure to temperatures up to an around 100C. Many endospore-forming bacteria are well known for the possible pathological dangers they hold. Therefore, it is vital develop methods by which these bacteria are effectively and efficiently destroyed. The core purpose of a sterilizing agent is that it possesses the ability to be biocidal. A biocide is a microorganism or a chemical substance that has the capability of killing living organisms (Prescott et al., 2005). There are many methods by which sterility of liquids and solids can be achieved, methods such as; heat, filtration, radiation or chemicals (Prescott et al., 2005). Out of these methods, the most effective option is heat. This includes both moist and dry heat.

The method of dry heat sterilization is also known as incineration. This process involves the complete removal of microorganisms off an object by exposing these microorganisms to exceptionally high temperatures, causing a complete disintegration and oxidation of all the cellular components (Goering et al., 2004). While this technique is effective in disintegrating the cellular structures of most microorganisms, it requires a long exposure time to a high temperature for it to have the desired effect (1 hour at 160-180°C)(Goering et al., 2004). While this process may be useful when using materials prone to corrosion or water damage, dry heat is expensive, time consuming and cannot be used with materials which are sensitive to heat (Goering et al., 2004).

In this experiment, the way in which we aim to achieve sterilization is by the use of an autoclave. The autoclave is a steam sterilizer that integrates high temperature and high pressure in achieving sterilisation (Prescott et al., 2005). There are two types of sterilizers. The first type of steam sterilizer is the high-speed pre-vacuum sterilizer (HSPS). The procedure by which HPSS acts to achieve sterilization is that steam enters the sterilizing chamber. Since air is heavier than steam, it is pushed under the steam and out the bottom of the sterilizing chamber through a draining vent (Ratula and Weber, 1999). It is important that the air and steam don’t mix; therefore HSPS has a vacuum pump that ensures that the air is removed from the sterilization chamber. Without the action of the vacuum pump, the air and steam will mix rendering the steam less effective (Ratula and Weber, 1999). The second type of steam sterilizer is the gravity displacement sterilizer (GDA). The mechanism by which the GDA operates is similar to the HSPS, except for the fact that it doesn’t contain a vacuum pump that removes the air from the sterilization chamber. The HSPS method is more effective than the GDA method, this is because it acts much faster and has instantaneous steam penetration.

The accuracy and reliability of the sterilization process can be altered by various confounding factors such as water hardness, pH, the presence of moisture or oil or even the ‘bio burden’ of the object (Goering et al., 2004). To combat this degree of uncertainty, there are a wide array of indicators which can confirm whether the sterilization process was successful (van Doornmalen, 2008).

A biological indicator that commonly used to confirm whether sterilization...
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