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Health Professionals > Endoscope Reprocessing

2.1 Cleaning, Disinfection & Sterilisation

OBJECTIVES

This module will look at sterilisation and disinfection. It covers the cleaning, disinfecting and sterilisation agents that are utilised in endoscopy and explores the factors that impact on their efficacy.

After completion of this module you will be able to:

DEFINITIONS AND SPAULDING'S CLASSIFICATION

Sterilisation refers to a physical or chemical process that completely destroys or removes all forms of viable microorganisms from an object, including spores. Sterility is an absolute condition - an item is either sterile or not sterile - there is no such thing as 'partially sterile'.

When describing a sterilization process, it is impossible to say that the chance of an organism surviving a process is zero. For medical equipment, it is acceptable to achieve a sterility assurance level of one in a million chances of a single organism surviving the process. Achieving this level of sterility assurance is dependent on the reduction of bioburden. Reduction of bioburden can only be achieved through thorough cleaning.

In the healthcare setting sterility is usually achieved by either steam under pressure, dry heat, ethylene oxide gas (ETO), low temperature hydrogen peroxide plasma or automated peracetic acid systems. When chemicals are used to achieve sterilisation of an object they are referred to as chemical sterilants. These same agents used for shorter exposure periods may also be part of the disinfection process. Only chemicals registered with the Therapeutic Goods Administration (TGA) as sterilants under Therapeutic Goods Order (TGO) 54 can be claimed to be sterilants.

Disinfection describes a process that eliminates many or all pathogenic microorganisms on inanimate objects, with the exception of bacterial spores. Disinfection can be accomplished by a number of means that include heat and chemicals. Terminology, which has been adopted by the Center for Disease Control (CDC) and is now widely used, describes disinfectants in terms of their activity as set out below:

In 1968 Earle Spaulding devised a rational approach to disinfection and sterilisation. This is now referred to as Spaulding's classification and it has been refined and retained over the years because it is so clear and logical. Spaulding believed that instruments and equipment should be cleaned and reprocessed according to the level of risk associated with their intended use. The three categories he described were critical, semicritical and noncritical as in the table below.

Level of risk

Application

Process

Critical
Entry or penetration into sterile tissue, cavity or bloodstream
Sterility required
Semi-critical
Contact with intact non sterile mucosa or non intact skin
Sterilisation preferred where possible.If sterilisation not possible then high-level chemical disinfection required.
Non-critical
Contact with intact skin
Clean as necessary with detergent and water

Flexible endoscopes come under the semi-critical category and ideally they should be sterilised. Because of their structural complexity and fragility flexible endoscopes cannot withstand the heat of steam sterilisation. There is currently no existing process that can guarantee sterility of flexible endoscopes.

Professional societies worldwide recommend that flexible endoscopes should be subjected to high level disinfection as a minimum level of reprocessing.

Endoscopic accessories which are used to enter tissue or the vascular system, such as biopsy forceps and all accessories for E.R.C.P. must be sterile.

There are a number of factors that may nullify or limit the efficacy of sterilisation and disinfection processes. These will be discussed in the next section and include:

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Last Updated: 29 August 2011
Last Reviewed: 29 August 2011