ASTM E1766-95

Standard Test Method for Determination of Effectiveness of Sterilization Processes for Reusable Medical Devices

SCOPE
1.1 This test method covers a reproducible procedure for testing processes used to sterilize reusable medical devices (instruments). This test method is not designed to validate a sterilization process, but tests an established sterilization cycle or process. It is a practical test of the effectiveness of a sterilization process applied to reusable medical devices. Bacterial spores more resistant to the test sterilant than the natural bioburden of the instrument are used as the test organisms. Commercially available liquid suspensions of bacterial spores are used to inoculate the instruments.  
1.2 This test method is intended for reusable medical devices cleaned in accordance with the device manufacturer's instructions and prepared for sterilization in accordance with the instructions for the sterilization process being used.  
1.3 This test method assumes that cleaned, reusable medical devices will be free of visible soil but may have remaining adherent bioburden. A worst-case bioburden can be represented by suspensions of bacterial endospores, which are commercially available for monitoring chemical or physical sterilization processes. These endospores should have a verifiable resistance (D value) to the specific process and sterilant being evaluated.  
1.4 It is impractical to test for the sterility of some devices by immersion in growth medium because of their complexity, size, and availability (for long-term incubation) or adverse effects on the devices from long-term immersion. Therefore, elution, rinsing, or swabbing techniques are used to recover test organisms from inoculated devices.  
1.5 A recovery control will be included by inoculation of a test device and use of the elution methods without applying the sterilization process being tested. A minimal recovery of 10  colony-forming unit (CFU)/mL per device is required for the recovery control.  
1.6 Results of the recovery control and process test cycle are compared to determine the effectiveness of the sterilization process.  
1.7 Results of the recovery control and applied inoculum are compared to determine the recovery efficiency, if desired.  
1.8 The procedure should reveal that tested devices are free of recoverable microorganisms when five or more consecutive tests are conducted.  
1.9 A knowledge of microbiological techniques is required to conduct these procedures.  
1.10 The values stated in SI units are to be regarded as the standard.  
1.11 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Dec-1994
• Technical Committee: E35 - Pesticides, Antimicrobials, and Alternative Control Agents
• Drafting Committee: E35.15 - Antimicrobial Agents

Relations

• Replaced By: ASTM E1766-95(2002) - Standard Test Method for Determination of Effectiveness of Sterilization Processes for Reusable Medical Devices
• Effective Date: 10-Oct-2002
• Referred By: ASTM F3127-22 - Standard Guide for Validating Cleaning Processes Used During the Manufacture of Medical Devices
• Effective Date: 01-Jan-1995

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 1766 – 95
Standard Test Method for
Determination of Effectiveness of Sterilization Processes for
Reusable Medical Devices
This standard is issued under the fixed designation E 1766; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.7 Results of the recovery control and applied inoculum are
compared to determine the recovery efficiency, if desired.
1.1 This test method covers a reproducible procedure for
1.8 The procedure should reveal that tested devices are free
testing processes used to sterilize reusable medical devices
of recoverable microorganisms when five or more consecutive
(instruments). This test method is not designed to validate a
tests are conducted.
sterilization process, but tests an established sterilization cycle
1.9 A knowledge of microbiological techniques is required
or process. It is a practical test of the effectiveness of a
to conduct these procedures.
sterilization process applied to reusable medical devices. Bac-
1.10 The values stated in SI units are to be regarded as the
terial spores more resistant to the test sterilant than the natural
standard.
bioburden of the instrument are used as the test organisms.
1.11 This standard does not purport to address all of the
Commercially available liquid suspensions of bacterial spores
safety concerns, if any, associated with its use. It is the
are used to inoculate the instruments.
responsibility of the user of this standard to establish appro-
1.2 This test method is intended for reusable medical
priate safety and health practices and determine the applica-
devices cleaned in accordance with the device manufacturer’s
bility of regulatory limitations prior to use.
instructions and prepared for sterilization in accordance with
the instructions for the sterilization process being used.
2. Referenced Documents
1.3 This test method assumes that cleaned, reusable medical
2.1 ASTM Standards:
devices will be free of visible soil but may have remaining
D 1193 Specification for Reagent Water
adherent bioburden. A worst-case bioburden can be represented
E 1054 Practices for Evaluating Inactivators of Antimicro-
by suspensions of bacterial endospores, which are commer-
bial Agents Used in Disinfectant, Sanitizer, Antiseptic, or
cially available for monitoring chemical or physical steriliza-
Preserved Products
tion processes. These endospores should have a verifiable
resistance (D value) to the specific process and sterilant being
3. Terminology
evaluated.
3.1 Definitions:
1.4 It is impractical to test for the sterility of some devices
3.1.1 bioburden—the number and types of viable microor-
by immersion in growth medium because of their complexity,
ganisms that contaminate a device.
size, and availability (for long-term incubation) or adverse
3.1.2 CFU—colony-forming unit.
effects on the devices from long-term immersion. Therefore,
3.1.3 inoculum—the number (usually specified as CFUs)
elution, rinsing, or swabbing techniques are used to recover test
and type (genus and species) of viable microorganisms used to
organisms from inoculated devices.
contaminate a given sample or device.
1.5 A recovery control will be included by inoculation of a
3.1.4 sporicidal agent—any chemical or physical agent that
test device and use of the elution methods without applying the
6 kills spores.
sterilization process being tested. A minimal recovery of 10
3.1.5 sterilant—any sterilizing agent.
colony-forming unit (CFU)/mL per device is required for the
3.1.6 sterile—a state of being free of living organisms.
recovery control.
3.1.7 sterilization cycle or process—a physical or chemical
1.6 Results of the recovery control and process test cycle are
process that has been demonstrated to meet applicable criteria
compared to determine the effectiveness of the sterilization
for sterilization as defined by AAMI.
process.
3.1.8 sterilizer—any device using a chemical or physical
process that produces sterile materials.
This test method is under the jurisdiction of ASTM Committee E-35 on 3.2 Definitions of Terms Specific to This Standard:
Pesticides and is the direct responsibility of Subcommittee E35.15 on Antimicrobial
Agents.
Current edition approved Nov. 10, 1995. Published January 1996. Annual Book of ASTM Standards, Vol 11.01.
2 4
Oxborrow, G. S., and Berube, R., “Sterility Testing—Validation of Sterilization Annual Book of ASTM Standards, Vol 11.05.
Processes, and Sporicide Testing,” Disinfection, Sterilization, and Preservation, See “Guideline for Industrial Ethylene Oxide Sterilization of Medical Devices”
Block, S. S., 4th Edition, Lea and Febiger, Philadelphia, PA, 1991, pp. 1047–1058. (ST27), AAMI, Arlington, VA, 1992, for typical criteria.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 1766
3.2.1 applied inoculum—the estimated count of the suspen- 6. Apparatus
sion of bacterial spores expressed as CFU/mL used to inoculate
6.1 Syringes, 10 to 50 mL, sterile.
the test devices. This value may be used if the efficiencies of
6.2 Sterile Cotton Swabs.
the recovery methods are determined.
6.3 Sterile Petri Dishes.
3.2.2 process test cycle—a complete sterilization cycle that
6.4 Sterile Test Tubes, to hold 10 mL.
uses all parameters of the sterilization process as dictated by
6.5 Sterile Glass Bottles, to hold 50 mL.
the manufacturer.
6.6 Steam Sterilizer.
3.2.3 recovery control—the CFU recoverable from a device
6.7 Water Bath,48 6 2°C.
following inoculation and optional drying of the spore suspen-
6.8 Incubator(s),35 6 2°C and 55 6 2°C.
sion in or on the unprocessed device. The recovery of $10
6.9 Colony Counter.
CFUs per device is required.
6.10 Medical Device, precleaned in accordance with the
3.2.4 recovery effıciency—a measure of the recovery of
manufacturer’s instructions.
inoculated organisms from a device may be determined when
6.11 Disposable or Reusable Membrane Filter Apparatus,
necessary. The recovery efficiency may be expressed as the
sterile, 0.45-μm pore size.
ratio of the CFU from the recovery control compared to the
6.12 Micropipette, calibrated to dispense 5 to 20 μL.
CFU of the applied inoculum. This value is multiplied by 100
6.13 Other devices or apparatus specified by the sterilant,
to express efficiency as a percent. It is recommended that a
medical device, or sterilizer manufacturer.
minimum of three tests be performed when estimating recovery
7. Reagents
efficiency.
3.2.5 reusable medical devices—any medical device that is
7.1 Purity of Reagents—Reagent grade chemicals shall be
claimed to be usable after reprocessing.
used in all tests. Unless otherwise indicated, it is intended that
3.2.6 spore—a bacterial endospore. (Strain identification
all reagents conform to the specifications of the Committee on
and the means used to identify whether the vegetative or spore
Analytical Reagents of the American Chemical Society where
state is present should be indicated.)
such specifications are available. Other grades may be used,
3.2.7 worst-case—the intentional exaggeration of one or
provided it is first ascertained that the reagent is of sufficiently
more parameters of a test compared to normal clinical condi-
high purity to permit its use without lessening the accuracy of
tions.
the determination.
7.2 Purity of Water—Unless otherwise indicated, references
4. Summary of Test Method
to water shall be understood to mean reagent water as defined
4.1 Percent recovery of inoculum may be used to ensure
by Type III of Specification D 1193.
reproducible inoculation and recovery techniques.
7.3 Media:
4.2 The test method is performed by contaminating the
7.3.1 Type III or Better ASTM Water, for making broths and
cleaned reusable medical device with a bacterial endospore
elution fluids.
suspension.
7.3.2 Sterile USP Fluid D —(elution fluid), containing
4.3 After inoculation, and drying, if required, the device is 9
polysorbate 80 or stripping solution containing 0.4 g KH PO ,
2 4
prepared and processed according to the sterilant or sterilizer
10.1 g Na HPO , and 1.0 g.
2 4
manufacturer’s instructions.
7.3.3 Isooctylphenoxypolyethoxy Ethanol (Triton X-100),
4.4 Following the sterilization process, the test devices are
in 1-L distilled water adjusted to pH 7.8.
sampled using specified elution techniques to recover any
7.3.4 Soybean-Casein Digest Broth, USP, single or double
surviving spores.
strength, with neutralizers for the test sterilant, as appropriate,
and a volume acceptable for each test.
5. Significance and Use
7.3.5 Soybean-Casein Digest Agar, USP, single or double
5.1 The test method is designed to demonstrate that all
strength, with neutralizers for the test sterilant, if appropriate;
accessible surfaces and internal recesses or lumina of previ-
10 to 50 mL in tubes or bottles, tempered to 48 6 2°C.
ously cleaned, reusable medical devices can be rendered free of
7.4 Test Organisms/Spore Suspension:
recoverable microorganisms when processed in a specified
7.4.1 For moist heat sterilization, standardized spore sus-
sterilizer cycle.
pensions of Bacillus stearothermophilus containing nominally
5.2 Surviving spores are recovered by swabbing, brushing,
10 CFU/mL and meeting USP resistance criteria for steam
or irrigating with an elution fluid. Recovery methods may be
enhanced by mechanical action, sonication, and repeated
flushing with elution fluid.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
NOTE 1—The spore inoculation technique described in this test method
listed by the American Chemical Society, see Analar Standards for Laboratory
is only one of the available procedures for testing the sterilization of
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
devices. Spores on paper strips (biological indocators) are a traditional
and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
tool used to develop and monitor sterilization cycles and are also MD.
United States Pharmacopeia, XXII, “Sterility Tests, Diluting and Rinsing
appropriate for the evaluation of sterilization of medical devices.
Fluids,” Rand McNally, Taunton, MA, 1990, p. 1484.
Williamson, P., “Quantitative Estimation of Cutaneous Bacteria,” Skin Bacteria
...