Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Process control in response to analysis
Reexamination Certificate
2000-02-04
2002-08-06
Till, Terrence R. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Process control in response to analysis
C422S001000, C435S004000, C435S029000, C435S031000
Reexamination Certificate
active
06428746
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods for determining the efficacy of decontamination procedures, and more particularly, to a method for testing the efficacy of decontamination procedures for endoscopes and other lumened surgical instruments.
BACKGROUND OF THE INVENTION
Prior to placing any surgical instrument within a patient, the instrument should be decontaminated (i.e., cleaned, disinfected, sterilized and/or water-rinsed) to avoid infecting the patient with contaminants or microorganisms on the instrument. Decontamination is especially challenging for lumened instruments, such a flexible endoscopes, which are repeatedly contaminated and decontaminated. Endoscopes are particularly difficult to decontaminate due to their design, which includes a variety of internal channels that are difficult to clean and access.
Medical professionals have an ever-increasing variety of decontamination methods from which to select. Selecting an effective decontamination method would be easier if an evaluation method existed to determine the efficacy of different decontamination methods. Medical professionals could use such an evaluation method to verify and document that they adequately decontaminated their instruments prior to surgery.
Users and suppliers of decontamination equipment and accessories (e.g., detergents and sterilants) would also be aided by a method for determining the efficacy of different decontamination methods.
Surgical instrument manufacturers (e.g., flexible and rigid endoscope manufacturers) would also be aided by a method for determining the efficacy of different decontamination methods. These manufacturers potentially could show that their instruments can be effectively decontaminated, and could specify that the end user employ a specific decontamination method that has been verified as adequate (i.e., validated).
All references cited herein are incorporated herein by reference in their entireties.
SUMMARY OF THE INVENTION
A method determines the efficacy of a decontamination procedure. The method includes providing a test object and a control object. The test object is contaminated with a first known amount of inoculum that includes microorganisms. The control object is contaminated with a second known amount of the inoculum. The first known amount of inoculum and the second known amount of inoculum is substantially the same. The decontamination procedure is performed on the contaminated test object but not on the contaminated control object. The microorganisms from the decontaminated test object and the contaminated control object are recovered. A number of microorganisms recovered from the decontaminated test object is compared with a number of microorganisms recovered from the contaminated control object. The decontamination procedure is deemed effective when the number of microorganisms recovered from the decontaminated test object is at least 3 logs less than the number of microorganisms recovered from the contaminated control object.
Another embodiment of the method includes performing a first sampling technique on the decontaminated test object and a second sampling technique on the contaminated control object. The first sampling technique and the second sampling technique are the same and are operative to recover the microorganisms from respective ones of the decontaminated test object and the contaminated control object. The decontamination procedure is deemed effective relative to the sampling technique when the number of microorganisms recovered from the decontaminated test object is at least 3 logs less than the number of microorganisms recovered from the contaminated control object.
Conventional methods for evaluating the efficacy of a decontamination process that do not use control instruments can yield erroneous results. For example, a known amount of an inoculum of viable microorganisms is applied onto internal surfaces forming internal lumens of a test instrument. This instrument is decontaminated using a prescribed decontamination process. Typically, a sterile fluid is used for sampling the lumens. Usually, the sterile fluid is rinsed through one end of the lumen, collected aseptically at the opposite end of the lumen and then analyzed microbiologically.
The efficacy of the decontamination process is assessed by measuring and comparing the number of microorganisms recovered from fluid rinsed through the test instrument to the known number of microorganisms originally applied to the test instrument. The lower the number of recovered microorganisms, the more efficacious the process is presumed to be. If the fluid is found to be sterile, the lumen is assumed to be sterile due presumptively to the prescribed decontamination process having destroyed all of the microorganisms inoculated onto the lumen surfaces.
This conclusion might be erroneous, however. It cannot be assumed that because the rinsing fluid was sterile, the decontamination process must have destroyed all of the microorganisms. In order for this decontamination process to be valid, the sampling technique must recover every viable microorganism on the lumen surfaces after exposure to the decontamination process. The rinse sampling technique might be invalid because microorganisms that survive the decontamination process may adhere to the lumen surfaces and not be recovered during the rinse sampling technique. Thus, due to the limitations of the rinse sampling technique, the decontamination process may be presumed to have destroyed all of the microorganisms on the lumen surfaces when, in fact, some microorganisms may have survived but cannot be recovered by the sampling technique. The method uses a control object to remove this potential artifact from being introduced into the data.
DEFINITIONS
Bioburden: The number and type of viable microorganisms used to contaminate instruments.
CFU: Colony Forming Units.
CFU/ml: A concentration of microorganisms, expressed as colony forming units per unit milliliter of volume.
Cleaning: The removal of foreign materials, such as organic soil (e.g., protein and/or blood serum) and microorganisms, from an object such as, e.g., a medical instrument.
High-level Disinfection: The complete destruction and/or removal of all microbal life, except for high numbers of bacterial endoscopes.
Sterilization: The complete destruction and/or removal of all microorganisms.
Decontamination: The process of cleaning, disinfecting, sterilizing and/or water-rinsing an object. The object can be subjected to any combination or permutation of these steps.
Detergent solution: A solution used to aid in cleaning objects:
Automated decontamination: The use of an automated device to decontaminate objects.
Starting titre: The concentration of microorganisms (expressed as CFU/ml) used to contaminate both the control and test instruments.
Manual decontamination: The decontamination of objects without the aid of an automated device.
Accessible sites: Refers to those locations on a reusable medical instrument that can be accessed and decontaminated.
Inaccessible sites: Refers to those locations on a reusable medical instrument that cannot be accessed and decontaminated.
Worst-case conditions: The intentional exaggeration of one or more parameters to create a challenge unlikely to be encountered in the clinical setting.
Reusable medical instrument: Any medical instrument that is claimed by the manufacturer to be usable after being decontaminated.
Endoscope: A generic term for a medical instrument that is used to examine hollow viscera. Examples of flexible endoscopes include broncoscopes, gastroscopes and colonoscopes. Examples of rigid endoscopes include laparoscopes and arthroscopes. Flexible endoscopes typically include internal lumens, a complex valve system, and other surfaces that need to be decontaminated after each use.
Test cycle: Exposure of an instrument to at least one of the steps of the decontamination process (e.g., cleaning, disinfecting, sterilizing and/or rinsing).
Inoculum: A volume of the starting titre (CFU) of a type (genus and species) of viable mi
Muscarella Lawrence F.
Weber Frank E. J.
Blank Rome Comisky & McCauley LLP
Custom Ultrasonics Inc.
Till Terrence R.
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