GB2311222A

GB2311222A - Cold sterilant composition comprising an aqueous solution of lithium iodide and iodine

Info

Publication number: GB2311222A
Application number: GB9605651A
Authority: GB
Inventors: Mary Viktoria Kelemen
Original assignee: FERGUSON ANDREW JOHN DUNCAN
Current assignee: FERGUSON ANDREW JOHN DUNCAN
Priority date: 1996-03-18
Filing date: 1996-03-18
Publication date: 1997-09-24
Also published as: WO1997034488A1; EP0888061A1; AU2034397A; JP2000506881A; GB9605651D0

Abstract

A single-stage cold sterilant composition comprises an aqueous solution of lithium iodide and iodine and is suitable for use is the sterilisation of dental and surgical instruments, such as endoscopes.

Description

STERILANT COMPOSITION This invention relates to a sterilant composition and in particular a composition suitable for use in a single-stage "cold" sterilising procedure having particular applicability to the sterilisation of dental and surgical instruments such as endoscopes.

The usual method of sterilising surgical instruments is by autoclaving, i.e. by enclosing the instruments in a chamber and supplying steam under high pressure and at high temperature. Steam sterilising is very effective but has several disadvantages, including that the process is relatively slow; the steam sterilising apparatus cannot be conveniently located close to the area where the surgical instruments are to be used, and also cannot be used for delicate surgical instruments which have integral optics and sensors or other heat sensitive parts, such as endoscopes, which are likely to be damaged by steam and heat.

For the latter type of instruments 4cold" sterilising procedures have to be used.

Cold sterilising procedures at present employed usually involve chemicals such as ethylene oxide, peracetic acid, formaldehyde, gluteraldehyde or hydrogen peroxide. However, there are also disadvantages in these procedures in that the chemicals are not easy to handle, being toxic, corrosive and/or inflammable and may also cause dermatitis and other harm to persons involved in the procedures. Additionally, chemical procedures usually require relatively long periods of time and consequently may restrict use of the surgical equipment; the temptation may then be present to re-use such equipment before it has been effectively re-sterilised.

Cold cleaning procedures are known for example from EP 0 038 168 in which surgical instruments such as endoscopes are first washed with a detergent liquid and are then washed with a liquid disinfectant.

However such procedures are not sterilisation procedures. Sterilisation destroys all life forms including, in particular, bacterial spores, whereas disinfection only implies the absence of pathogenic life forms. Thus procedures such as described in EP 0 038 168 do not actually sterilise surgical instruments, and a separate sterilisation procedure is necessary. Additionally they involve risks of splashing with chemicals, and with blood and body tissue and fluids from the spraying of the surgical instruments with detergents, and the latter risks cannot be ignored with the growing prevalence of AIDS.

The trend in surgical techniques, particularly microsurgical techniques, has been towards operations without general anaesthetic or even without local anaesthetic, thereby increasing the speed of surgical operations and creating a demand for re-sterilised surgical instruments to be available more quickly. On the other hand surgical instruments such as endoscopes tend to be costly and therefore it is impractical to have a large number of such instruments available for use in rotation.

In W092/11875 there is described and claimed a process for sterilising surgical instruments at ambient temperature which process comprises the steps of firstly decontaminating the surgical instrument in a closed environment by washing it in a detergent liquid having bactericidal properties to remove any blood, body tissue and/or fluid adhering to the instrument, and secondly washing the instrument in said closed environment in a strongly bactericidal liquid to sterilise the instrument.

In the above method it is particularly preferred that the detergent liquid used is an aqueous solution of a quaternary ammonium salt, alkyltrimethyl ammonium bromides being particularly preferred, for example, Cetrimide which is a straight chain C16 alkyltrimethyl ammonium bromide, as they are both surfactants and strong bactericides. The quaternary ammonium salt is preferably used at a concentration of the order of about 1% by weight. Also, the strongly bactericidal liquid is preferably an aqueous solution of iodine, used at a preferred concentration of the order of about 0.2% by weight.

The above process has proved to be a particularly effective sterilising procedure. However, the process is, as will be apparent, a two-stage process and this in itself causes the procedure to be of relatively long duration, typically one hour to achieve sterilisation and as is explained above the advances in surgical techniques has increased the speed of surgical operations thus creating a demand for re-sterilised surgical instruments to be made available more quickly, and since surgical instruments such as endoscopes tend to be very costly their downtime has to be reduced as much as possible.

There is therefore a continuing demand for a sterilisation procedure which is faster than those hitherto proposed and known but which maintains the advantage of the previously described process in using non-toxic, non-flammable and preferably colourless agents and, ideally, being a single-stage procedure rather than a two-stage process. In particular, there is a demand for such a single-stage process which effects sterilisation preferably within a period of 30 minutes.

It is known that solutions of iodine in aqueous potassium iodide are particularly effective sterilising agents but unfortunately such solutions are not effective against spores, at least within a reasonable period of time.

It has now been discovered that a solution of iodine in aqueous lithium iodide is effective both against many microorganisms and cells, as well as spores. The present invention in fact provides a single-stage cold sterilant composition comprising an aqueous solution of lithium iodide and iodine. The solution is preferably buffered at an acid pH of between 3 and 5, optimally pH 4, using for example a sodium acetate/acetic acid buffer at 0.2M.

The iodine is preferably present in the solution at a concentration of at least 0.5% by weight/volume up to the limit of solubility of iodine in the solution. The concentration of lithium iodide is preferably at least 1% by weight/volume but it is envisaged that a concentration of down to about 0.58 may be effective. Typically the sterilant composition may comprise a buffered aqueous solution of 1% by weight/volume lithium iodide and 1.5 by weight/volume iodine.

The invention also provides a single-stage method of sterilisation at ambient temperature which comprises bringing the article to be sterilised into contact with the sterilant composition as described above for a period of time of preferably not longer than 30 minutes but sufficient to sterilise the article.

It is not known precisely why the cold sterilisation composition of the present invention is so effective. However, it is speculated that the small size of the lithium ions, as compared with the size, for example, of potassium ions, may enable the lithium ions to penetrate through small orifices in the otherwise relatively impenetrable outer coating of the spore and thereby to cause initial disruption of the walls of the spore which enables the iodine to gain access to the spore and to perform its usual sterilising effect. Alternatively or additionally it may be that the lithium ions partially replace calcium, magnesium or iron ions, or any other ions which may be present in the structure of the cell wall. Such substitution may be the cause of distortion or other effects which weaken the cell wall structure and thereby permit the iodine to penetrate to the interior of the spore.

The actual procedures for use of the cold sterilant composition of the present invention require no detailed description as suitable procedures will be readily apparent to those skilled in the art.

Claims

CLAIMS:

1. A single-stage cold sterilant composition comprising an aqueous solution of lithium iodide and iodine.

2. A single-stage cold sterilant composition as claimed in claim 1 wherein the lithium iodide is present in a concentration of at least 1% by weight/volume.

3. A single-stage cold sterilant composition as claimed in claim 1 or claim 2 wherein the iodine is present in a concentration of at least 0.5% by weight/volume, up to the limit of solubility of iodine in the solution.

4. A single-stage cold sterilant composition as claimed in any one of the preceding claims wherein the solution is buffered to a pH in the range of 3 to 5, preferably 4.

5. A single-stage cold sterilant composition as claimed in any one of the preceding claims wherein the concentration of lithium iodide is approximately 1% and concentration of iodine is approximately 1.5%.

6. A single-stage method of sterilisation at ambient temperature which comprises bringing the article to be sterilised into contact with the sterilant composition as claimed in any one of the preceding claims for a period of time of preferably no longer than 30 minutes but sufficient to sterilise the article.

7. A single-stage cold sterilant composition as claimed in claim 1 substantially as hereinbefore described.