Endoscopes are increasingly being used in medical diagnosis and therapy When used as directed the endoscope becomes grossly soiled and massively infected with microorganisms which are present in body cavities, on the mucous membrane, and in the blood. Accordingly the instruments must be thoroughly cleaned and disinfected after each use. Endoscopes are precision instruments which are made from a combination of materials. They are difficult to clean in view of the sensitivity of the materials involved to chemical attack and because they have narrow lumens making access to and cleaning of interior surfaces difficult.
Until the last decade, it was common for soiled instruments to be placed on a towel or in a covered pan until they were sent to a centralised service where they were scrubbed, washed and either sterilised in a steam autoclave (if not heat sensitive) or chemically (e.g. with formaldehyde). In the last decade, there has arisen a particular concern to avoid transmission of very serious and sometimes fatal diseases such as may be carried in blood and tissue, for example hepatitis B, HIV, and other infections.
Nowadays, contaminated endoscopes and other medical instruments are typically treated in a first bath (“presoak” or “cleaning” bath) containing one or a combination of anionic and non ionic surfactants. The first bath may optionally include one, or a combination of enzymes, adapted to digest biological contaminants including cellular material, blood and other body fluids. Enzyme containing pre-soaking liquids are significantly more efficient in removing water insoluble and protein soils and are now considered the industry standard. In the case of surgical instruments requiring to be sterilised, the instruments are typically then removed from the first bath, washed free of enzyme solution and other residues, and then deposited in a second bath containing a chemical sterilizing agent (for example, glutaraldehyde). The first bath container is subsequently washed and then furnished with a fresh enzyme solution so that the process may be repeated. The necessity for separate cleaning and sterilizing baths arises since enzymes are denatured by all known sterilizing agents and since sterilizing agents are deactivated by enzymes (as enzymes are proteins). Accordingly it has to date proved impossible to provide a “single bath” cleaning and sterilizing treatment, although a two part system involving an enzyme treatment followed by addition of a phenolic disinfectant in the same bath has been proposed.
Sterilisation protocols are followed to prevent cross infection and therefore instruments used with one patient are not combined with those which may have been used with another in the presoak bath. It is noteworthy that the presoak is not passive. Staff are instructed to syringe detergent liquor through all the lumens, to brush biopsy channels, etc. A colonoscope requires up to 14 manual brushing-syringing-plugging-unplugging operations. It is usual for staff to wear latex gloves when handling instruments into or out of the baths and when performing such like operations.
The present inventor has observed that currently used procedures, while effective for preventing crossinfection between patients, in fact exposes medical and/or hospital staff to hitherto unrecognised health and safety risks. By virtue that the enzymes of the first bath digest the biological secretions holding the microorganisms, thus releasing them within the bath, and surfactants efficiently disperse them, the fluid content of the first bath is itself readily contaminated to high levels with infectious material. Contrary to the belief of some hospital staff, enzymes do not kill bacteria but rather release them. The present inventor has measured bacterial counts in excess of 1×109 colony forming units (“cfu”) per sq. cm. on instruments entering the first bath
Staff are therefore at risk of infection (i) from splashes from the first bath either during scrubbing to release contaminants or during draining the first bath (or from splashes if an instrument is accidentally dropped into the bath), (ii) from glove failures (latex gloves have a “pinhole” failure rate of about 12%), (iii) from accidental glove immersion above the wrist line, (iv) from finger stick incidents in the bath resulting in glove and sometimes dermal penetration, (v) from aerosols created by brushes and syringes. In addition the wall surface of the first bath remains contaminated after the bath has been emptied and if not itself disinfected may be handled by unprotected staff. The last mentioned risk may be minimised by performing the sterilisation step immediately after the digestion step in the same container, but this does not avoid any of the other hitherto unrecognised risks and is wasteful in use of excess sterilant.
In some cases instruments may not be required to be sterilised, for example with spatulas, and holders which do not penetrate the body tissue, hair dressing implements and the like, it may be sufficient to disinfect the instruments to an appropriate standard. In such cases it would be desirable to provide a cleaning and disinfecting treatment capable of meeting the required standards with a single composition.
Any discussion of the prior art herein is not to be construed as indicative of the state of the common general knowledge in the field.
It is the object of the invention to avoid or ameliorate the above discussed disadvantages of prior art, or at least provide a commercial alternative to the prior art.
It is an object of preferred embodiments of the present invention to avoid or at least ameliorate the risk of infection to persons cleaning medical instruments by such procedures.
It is a further object of at least some of the preferred embodiments to provide a single step cleaning and disinfecting composition for use in cleaning medical instruments.
Preferred embodiments of the invention also address the risk of cross infection of instruments by virtue of multiplication of microorganisms, if any, which remain on the bath walls after each cycle of instrument cleaning.
It is an object of some embodiments of the invention to provide simple means for cleaning and disinfecting surfaces which require to be disinfected