Disinfection * - the reduction or destruction of all vegetative microorganisms, mycobacteria, small or nonlipid viruses, medium or lipid viruses, fungal spores, and some but not all bacterial spores to a level appropriate for safe use on a patient.

*This is definition of "high-level" disinfection.

General procedures

Disinfection of endoscopes should be performed in dedicated rooms by trained staff at the beginning and at the end of each patient list, as well as between patients. The European practice of disinfecting endoscopes just before patient use is not always practiced or recommended in other countries. However, reprocessing the endoscope immediately after use is a commonly accepted standard. An exception can be made when the endoscope is stored in a clean environment. Recommendations for effective disinfection with a liquid chemical germicide include:

- using an automatic endoscope reprocessor

- performing disinfection in a dedicated area with atmospheric extraction facilities

- flushing high-level disinfectant or chemical sterilant throughout the endoscope at the correct temperature and for the correct duration

- concluding disinfection by rinsing with sterile or filtered water or alcohol

- drying each endoscope properly with forced air

For the protection of staff during the disinfection procedure the following apparel or equipment is recommended

- long-sleeved waterproof gowns which are changed between patients

- gloves long enough to cover the forearms

- goggles to prevent conjunctival irritation and protect from splashes

- disposable charcoal-impregnated face masks to reduce inhalation of vapor

- an approved vapor respirator available for spillage or other emergencies

There are various classes of disinfectants available. Chemical sterilants are strong disinfectants that kill all microorganisms, including spores, after prolonged exposure; the exposure times recommended by the manufacturer and in the scientific literature should be adhered to. After shorter exposure periods of up to 45 minutes chemical sterilants kill all microorganisms except large numbers of bacterial spores. Other disinfectants may be biocidal for mycobacteria, vegetative bacteria, most viruses and most fungi, but do not necessarily kill bacterial spores. Some disinfectants kill most vegetative bacteria, some fungi and some viruses within 10 minutes. Germicides differ markedly among themselves primarily in their antimicrobial spectrum and rapidity of action. It is important to note that an alcohol flush should not be used as an alternative to disinfection as alcohol is expensive and hazardous to use.

Importance of disinfection

Introduction Flexible endoscopes are exposed to body fluids and other contaminants. Procedural errors in decontamination, defective equipment and failure to follow disinfection guidelines are major factors contributing to transmission of infection during endoscopy. Other important risk factors include inadequate cleaning, use of older endoscopes with surface and working channel irregularities, and contamination of water bottles or irrigating solutions. Further risks are associated with the design or maintenance of automatic endoscope reprocessors, improper selection of disinfecting agents, inadequate drying and/or storage of endoscopes, and in particular incorrect connectors. In order to prevent transmission of infections, flexible gastrointestinal endoscopes (as well as other heat-sensitive endoscopes) require proper cleaning and - at a minimum - high-level disinfection following each use. However, some bacterial spores may survive disinfection if present in high numbers. Rigid endoscopes and most reusable accessories can be autoclaved. Unique features with respect to the disinfection of endoscopic equipment include the external surface, the internal channels for air, water and fluid aspiration, and the accessories. Efficacy of disinfection The disinfection process eliminates most, if not all, pathogenic microorganisms with the exception of bacterial spores. Disinfection is usually accomplished by the use of liquid chemicals or wet pasteurization, and its efficacy is affected by the following factors:

- prior cleaning of the object

- organic and inorganic load present

- type and level of microbial contamination

- concentration of the germicide and time of exposure to it

- presence of biofilms

- temperature and pH used for the disinfection process

Some pathogens are more difficult to eliminate in the endoscope disinfection process than others. These pathogens are in decreasing order of resistance to disinfectants/sterilization: 

- prions - e.g. Creutzfeldt-Jakob prion

- bacterial spores - e.g. Bacillus subtilisC

- coccidia - e.g. Cryptosporidium parvum

- mycobacteria - e.g. Mycobacterium tuberculosis, Mycobacterium terrae

- non-lipid or small viruses - e.g. poliovirus, coxsackie viruses

- fungi - e.g. Aspergillus species , Candida species

- vegetative bacteria - e.g. Staphylococcus aureus, Pseudomonas aeruginosa

- lipid or medium-sized viruses - e.g. HIV, herpes viruses, hepatitis B virus

Examinations via endoscopy should be avoided in patients with suspected or confirmed variant Creutzfeldt-Jakob disease (vCJD). If endoscopy is considered essential in such patients, either a dedicated endoscope should be used or an endoscope nearing the end of its life which can be reserved for use in similar patients. The vCJD prion is resistant to all forms of conventional sterilization. The risk of transmission of this agent is probably extremely low provided scrupulous attention to is paid to detail in the decontamination procedure after each patient. In particular, all accessible endoscope channels should be brushed with a disposable brush-tipped wire assembly designed for the purpose which has an appropriate length and diameter for each channel.

Disinfectants

General remarks The ideal disinfectant is effective against a wide range of organisms, including blood-borne viruses and prion proteins; compatible with endoscopes, accessories and endoscope reprocessors; non-irritant and safe for users; and permits environmentally friendly disposal. Disinfectants must be used at the correct temperature, and in accordance with the manufacturer's instructions and current recommendations in the literature. The disinfectants should be tested regularly with test strips and/or kits provided by manufacturers to ensure optimal activity of the products. Factors influencing the choice of disinfectant include

- dilution process

- stability of the solution

-  number of reuses possible

- direct cost

- indirect costs (e.g. appropriate automatic endoscope reprocessor, storage space, conditions for use, staff protection measures)