ASTM E1766-95(2007)
(Test Method)Standard Test Method for Determination of Effectiveness of Sterilization Processes for Reusable Medical Devices
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 106 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.
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.
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Designation: E1766 − 95(Reapproved 2007)
Standard Test Method for
Determination of Effectiveness of Sterilization Processes for
Reusable Medical Devices
This standard is issued under the fixed designation E1766; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope sterilization process being tested. A minimal recovery of 10
colony-forming unit (CFU)/mL per device is required for the
1.1 This test method covers a reproducible procedure for
recovery control.
testing processes used to sterilize reusable medical devices
1.6 Resultsoftherecoverycontrolandprocesstestcycleare
(instruments). This test method is not designed to validate a
compared to determine the effectiveness of the sterilization
sterilization process, but tests an established sterilization cycle
process.
or process. It is a practical test of the effectiveness of a
sterilization process applied to reusable medical devices. Bac-
1.7 Resultsoftherecoverycontrolandappliedinoculumare
terial spores more resistant to the test sterilant than the natural
compared to determine the recovery efficiency, if desired.
bioburden of the instrument are used as the test organisms.
1.8 The procedure should reveal that tested devices are free
Commercially available liquid suspensions of bacterial spores
of recoverable microorganisms when five or more consecutive
are used to inoculate the instruments.
tests are conducted.
1.2 This test method is intended for reusable medical
1.9 A knowledge of microbiological techniques is required
devices cleaned in accordance with the device manufacturer’s
to conduct these procedures.
instructions and prepared for sterilization in accordance with
1.10 The values stated in SI units are to be regarded as the
the instructions for the sterilization process being used.
standard.
1.3 This test method assumes that cleaned, reusable medical
1.11 This standard does not purport to address all of the
devices will be free of visible soil but may have remaining
safety concerns, if any, associated with its use. It is the
adherentbioburden.Aworst-casebioburdencanberepresented
responsibility of the user of this standard to establish appro-
by suspensions of bacterial endospores, which are commer-
priate safety and health practices and determine the applica-
cially available for monitoring chemical or physical steriliza-
bility of regulatory limitations prior to use.
tion processes. These endospores should have a verifiable
resistance (D value) to the specific process and sterilant being
2. Referenced Documents
evaluated.
2.1 ASTM Standards:
1.4 It is impractical to test for the sterility of some devices
D1193 Specification for Reagent Water
by immersion in growth medium because of their complexity,
E1054 Test Methods for Evaluation of Inactivators of Anti-
size, and availability (for long-term incubation) or adverse
microbial Agents
effects on the devices from long-term immersion. Therefore,
elution,rinsing,orswabbingtechniquesareusedtorecovertest
3. Terminology
organisms from inoculated devices.
3.1 Definitions:
1.5 A recovery control will be included by inoculation of a
3.1.1 bioburden—the number and types of viable microor-
test device and use of the elution methods without applying the
ganisms that contaminate a device.
3.1.2 CFU—colony-forming unit.
3.1.3 inoculum—the number (usually specified as CFUs)
This test method is under the jurisdiction of ASTM Committee E35 on
and type (genus and species) of viable microorganisms used to
Pesticides, Antimicrobials, and Alternative Control Agents and is the direct
contaminate a given sample or device.
responsibility of Subcommittee E35.15 on Antimicrobial Agents.
Current edition approved Nov. 1, 2007. Published November 2007. Originally
approved in 1995. Last previous edition approved in 2002 as E1766 – 95 (2002).
DOI: 10.1520/E1766-95R07. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Oxborrow, G. S., and Berube, R., “SterilityTesting—Validation of Sterilization contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Processes, and Sporicide Testing,” Disinfection, Sterilization, and Preservation, Standards volume information, refer to the standard’s Document Summary page on
Block, S. S., 4th Edition, Lea and Febiger, Philadelphia, PA, 1991, pp. 1047–1058. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1766 − 95 (2007)
3.1.4 sporicidal agent—any chemical or physical agent that 5. Significance and Use
kills spores.
5.1 The test method is designed to demonstrate that all
3.1.5 sterilant—any sterilizing agent.
accessible surfaces and internal recesses or lumina of previ-
ouslycleaned,reusablemedicaldevicescanberenderedfreeof
3.1.6 sterile—a state of being free of living organisms.
recoverable microorganisms when processed in a specified
3.1.7 sterilization cycle or process—a physical or chemical
sterilizer cycle.
process that has been demonstrated to meet applicable criteria
5.2 Surviving spores are recovered by swabbing, brushing,
for sterilization as defined by AAMI.
or irrigating with an elution fluid. Recovery methods may be
3.1.8 sterilizer—any device using a chemical or physical
enhanced by mechanical action, sonication, and repeated
process that produces sterile materials.
flushing with elution fluid.
3.2 Definitions of Terms Specific to This Standard:
NOTE 1—The spore inoculation technique described in this test method
3.2.1 applied inoculum—the estimated count of the suspen-
is only one of the available procedures for testing the sterilization of
sionofbacterialsporesexpressedasCFU/mLusedtoinoculate
devices. Spores on paper strips (biological indocators) are a traditional
the test devices. This value may be used if the efficiencies of
tool used to develop and monitor sterilization cycles and are also
the recovery methods are determined. appropriate for the evaluation of sterilization of medical devices.
3.2.2 process test cycle—a complete sterilization cycle that
6. Apparatus
uses all parameters of the sterilization process as dictated by
6.1 Syringes, 10 to 50 mL, sterile.
the manufacturer.
6.2 Sterile Cotton Swabs.
3.2.3 recovery control—the CFU recoverable from a device
following inoculation and optional drying of the spore suspen-
6.3 Sterile Petri Dishes.
sion in or on the unprocessed device. The recovery of ≥10
6.4 Sterile Test Tubes, to hold 10 mL.
CFUs per device is required.
6.5 Sterile Glass Bottles, to hold 50 mL.
3.2.4 recovery effıciency—a measure of the recovery of
6.6 Steam Sterilizer.
inoculated organisms from a device may be determined when
necessary. The recovery efficiency may be expressed as the
6.7 Water Bath, 48 6 2°C.
ratio of the CFU from the recovery control compared to the
6.8 Incubator(s), 35 6 2°C and 55 6 2°C.
CFU of the applied inoculum. This value is multiplied by 100
6.9 Colony Counter.
to express efficiency as a percent. It is recommended that a
minimumofthreetestsbeperformedwhenestimatingrecovery
6.10 Medical Device, precleaned in accordance with the
efficiency.
manufacturer’s instructions.
3.2.5 reusable medical devices—any medical device that is
6.11 Disposable or Reusable Membrane Filter Apparatus,
claimed to be usable after reprocessing.
sterile, 0.45-µm pore size.
3.2.6 spore—a bacterial endospore. (Strain identification
6.12 Micropipette, calibrated to dispense 5 to 20 µL.
and the means used to identify whether the vegetative or spore
6.13 Other devices or apparatus specified by the sterilant,
state is present should be indicated.)
medical device, or sterilizer manufacturer.
3.2.7 worst-case—the intentional exaggeration of one or
more parameters of a test compared to normal clinical condi-
7. Reagents
tions.
7.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
4. Summary of Test Method
all reagents conform to the specifications of the Committee on
4.1 Percent recovery of inoculum may be used to ensure Analytical Reagents of the American Chemical Society where
reproducible inoculation and recovery techniques.
such specifications are available. Other grades may be used,
provided it is first ascertained that the reagent is of sufficiently
4.2 The test method is performed by contaminating the
high purity to permit its use without lessening the accuracy of
cleaned reusable medical device with a bacterial endospore
the determination.
suspension.
7.2 Purity of Water—Unless otherwise indicated, references
4.3 After inoculation, and drying, if required, the device is
to water shall be understood to mean reagent water as defined
prepared and processed according to the sterilant or sterilizer
by Type III of Specification D1193.
manufacturer’s instructions.
4.4 Following the sterilization process, the test devices are
United States Pharmacopeia, XXIII, Rand McNally, Taunton, MA, 1995, pp.
sampled using specified elution techniques to recover any
200–206.
surviving spores. 6
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
See “Guideline for Industrial Ethylene Oxide Sterilization of Medical Devices” and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
(ST27), AAMI, Arlington, VA, 1992, for typical criteria. MD.
E1766 − 95 (2007)
7.3 Media: 8.5 Inoculation of Devices to Determine the Applied
7.3.1 Type III or Better ASTM Water, for making broths and Inoculum—These paragraphs describe the steps for enumerat-
elution fluids. ingtheCFUofsporesinoculatedontothemedicaldevicebeing
7.3.2 Sterile USP Fluid D —(elution fluid), containing tested. The spores are not subjected to drying or other
polysorbate80orstrippingsolution containing0.4gKH PO , treatments, as they might be when determining the recovery
2 4
10.1 g Na HPO , and 1.0 g. control (see 8.6).
2 4
7.3.3 Isooctylphenoxypolyethoxy Ethanol (Triton X-100), in
8.5.1 Surface Site Inoculation:
1-L distilled water adjusted to pH 7.8.
8.5.1.1 Micropipetter Method—Inoculate the surface di-
7.3.4 Soybean-Casein Digest Broth, US
...
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