ASTM E1837-96
(Test Method)Standard Test Method to Determine Efficacy of Disinfection Processes for Reusable Medical Devices (Simulated Use Test)
Standard Test Method to Determine Efficacy of Disinfection Processes for Reusable Medical Devices (Simulated Use Test)
SCOPE
1.1 This test method is intended to describe a procedure for testing the effectiveness of a disinfection process for reprocessing usable medical devices when it is tested with a challenge of vegetative cells including mycobacteria. Disinfection normally deals with testing activity against vegetative cells of bacteria, viruses, and fungi. Since this test method is process oriented, the user may wish to examine a variety of test organisms.
1.2 This test method is designed to provide a reproducible procedure to verify the effectiveness of a previously validated disinfectant or disinfection procedure for reusable medical instruments and devices.
1.3 this test method is not meant to define the effectiveness of or validation of the particular disinfection process used or its kinetics, but rather, it is devised to confirm the effectiveness of the disinfection process by simulating use situations with a particular test process using medical devices and instruments. Either manual or machine reprocessing can be tested.
1.4 this test method is intended for use with reusable cleaned and previously sterilized or disinfected (high level) medical instruments and devices. Endoscoped are described in this test method as a worst-case example for contamination and sampling. The selected sterilization or disinfectionprocesses, or both, should have been validated previously, as well as the effectiveness of rinsing for residual sterilant/disinfectant removal determined.
1.5 An inoculum with high numbers of selected microorganisms is applied to both test and control, cleaned and sterilized, or disinfected medical instruments. Strains of microorganisms with a recorded resistance to disinfectants are used to contaminate the instrument sites known or suspected to be the most difficult to reprocess.
1.6 It is impractical to test for recovery of survivors by immersion of some instruments, for example, endoscopes or some laproscopic instruments, in growth medium because of complexity, size, difficulty in long term incubation, or deterious effects resulting from incubation. Elution of organisms from the inoculated surfaces , therefore, may be performed to estimate the number of recoverable organisms. Immersion can be used for smaller instruments.
1.7 Control instruments are inoculated in the same manner as the test instruments and elution or immersion methods are performed to determine the number of organisms recoverable from the instrument. For channeled devides, such as endoscopes testing, the number of organisms recoverable from the instrument (inside and outside) will serve as the initial control count. It is expected that some fraction of the number of organisms inoculated will be lost in the process of inoculation/drying.
1.8 A testing procedure can be performed on a complete reprocessing cycle or can be limited to just the cleaning or disinfection portions of the cycle whether reprocessing is done in a machine or manually.
1.9 After the test cycle has been completed, remaining inoculated bacteria will be recovered from test instruments using the same elution procedures as for the control instruments.
1.10 Efficacy of a disinfection cycle or reprocessing cycle, or any part thereof, may be determined by comparison of the number of microorganisms recovered from the control instrument (initial recoverable control unit) to the recovery determined for the test instruments.
1.11 A knowledge of microbiological techniques is required to conduct these procedures.
1.12 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: E 1837 – 96
Standard Test Method to
Determine Efficacy of Disinfection Processes for Reusable
Medical Devices (Simulated Use Test)
This standard is issued under the fixed designation E 1837; 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.
INTRODUCTION
When special tests designed to register or validate a disinfection process currently are used, the
procedures, their statistical considerations (usually all negatives at a given time point), and the
physical problems of applying organisms to surfaces, such as sutures and unglazed porcelain carriers,
may cause inaccurate and confusing results. Practical, in-use testing of reprocessing techniques and
conditions are needed. Exaggerated conditions for testing can be achieved with the use of actual
instruments contaminated with high numbers of organisms. The addition of serum as an organic load
or hard water minerals as an inorganic load can be made to enhance worst-case conditions. When these
elements are coupled with the processing, as actually performed, the result is a structured test that is
a simulated-use procedure. This test method is designed to incorporate several elements of
reprocessing, including cleaning, rinsing, and disinfection (including optional treatment of the internal
channels of devices, such as endoscopes) with a terminal alcohol rinse rather than examining only the
effectiveness of the entire disinfection process. A simulated-use test to examine the effectiveness of
reprocessing procedures is valuable because several incidents of contamination of instruments in use
have been recorded with vegetative cells of bacteria, for example, Pseudomonas and the mycobacteria.
When this procedure is performed with a representative mycobacterial culture, it is necessary to use
a nonpathogenic strain such as Mycobacterium terrae (isolated from soil) that can be manipulated on
an open bench. This strain is used in tuberculocidal testing in Europe, and published information
shows comparable resistance to antimicrobials as that displayed by human tuberculosis strains of
Mycobacterium tuberculosis. This organism can be handled easily and grows faster than other test
strains, such as M. bovis. (1,2,3,4, and 5).
Because contamination of the surfaces of instruments has occurred from rinsing with tap water,
bacteria-free water should be used for all rinsing during reprocessing in this test procedure when a
water rinse step is part of the reprocessing directions.
1. Scope disinfectant or disinfection procedure for reusable medical
instruments and devices.
1.1 This test method is intended to describe a procedure for
1.3 This test method is not meant to define the effectiveness
testing the effectiveness of a disinfection process for reprocess-
of or validation of the particular disinfection process used or its
ing reusable medical devices when it is tested with a challenge
kinetics, but rather, it is devised to confirm the effectiveness of
of vegetative cells including mycobacteria. Disinfection nor-
the disinfection process by simulating use situations with a
mally deals with testing activity against vegetative cells of
particular test process using medical devices and instruments.
bacteria, viruses, and fungi. Since this test method is process
Either manual or machine reprocessing can be tested.
oriented, the user may wish to examine a variety of test
1.4 This test method is intended for use with reusable
organisms.
cleaned and previously sterilized or disinfected (high level)
1.2 This test method is designed to provide a reproducible
medical instruments and devices. Endoscopes are described in
procedure to verify the effectiveness of a previously validated
this test method as a worst-case example for contamination and
sampling. The selected sterilization or disinfection processes,
or both, should have been validated previously, as well as the
This test method is under the jurisdiction of ASTM Committee E-35 on
Pesticides and is the direct responsibility of Subcommittee E35.15 on Antibacterial
effectiveness of rinsing for residual sterilant/disinfectant re-
Agents.
moval determined.
Current edition approved Oct. 10, 1996. Published December 1996.
2 1.5 An inoculum with high numbers of selected microor-
The boldface numbers in parentheses refer to the list of references at the end of
this standard. ganisms is applied to both test and control, cleaned and
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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 1837
sterilized, or disinfected medical instruments. Strains of mi- 3.1.3 disinfectant—any biocidal chemical that produces ma-
croorganisms with a recorded resistance to disinfectants are terials free from vegetative microorganisms that may contami-
used to contaminate the instrument sites known or suspected to nate them and potentially cause infection.
be the most difficult to reprocess. 3.1.3.1 Discussion—The definitions included are the tradi-
1.6 It is impractical to test for recovery of survivors by tional ones. The user may choose to conform to other criteria
immersion of some instruments, for example, endoscopes or that specify elimination of a certain number of test microor-
some laproscopic instruments, in growth medium because of ganisms. Other definitions describe the action as application of
complexity, size, difficulty in long-term incubation, or deteri- a process resulting in elimination of microorganisms. Whatever
ous effects resulting from incubation. Elution of organisms criteria is selected, it should be stated before initiation of the
from the inoculated surfaces, therefore, may be performed to test procedure.
estimate the number of recoverable organisms. Immersion can 3.1.3.2 Discussion—A series of three definitions devised by
be used for smaller instruments. Spaulding (6, 7) separated the activity of germicides against
1.7 Control instruments are inoculated in the same manner spores and mycobacteria and non-lipid viruses and are there-
as the test instruments and elution or immersion methods are fore defined by activity against groups of microorganisms.
performed to determine the number of organisms recoverable These definitions are as follows:
from the instrument. For channeled devices, such as endo- (1) High-level disinfectants must inactivate bacteria en-
scopes testing, the number of organisms recoverable from the dospores, mycobacteria, non-lipid viruses, fungi, vegetative
instrument (inside and outside) will serve as the initial control bacteria, and lipid viruses. If exposure time is extended long
count. It is expected that some fraction of the number of enough, this type of germicide can be used as a sterilant.
organisms inoculated will be lost in the process of inoculation/ (2) Medium-level disinfectants inactivate mycobacteria, veg-
drying. etative bacteria, fungi including asexual spores, and lipid and
1.8 A testing procedure can be performed on a complete non-lipid viruses.
reprocessing cycle or can be limited to just the cleaning or (3) Low-level disinfection inactivate vegetative bacteria,
disinfection portions of the cycle whether reprocessing is done most fungi, and lipid viruses.
in a machine or manually. 3.1.4 disinfector, n—any device or physical process that
1.9 After the test cycle has been completed, remaining provides a biocidal process that produces materials free from
inoculated bacteria will be recovered from test instruments vegetative microorganisms that may contaminate them and
using the same elution procedures as for the control instru- potentially cause infection.
ments. 3.1.5 inoculum—the number (usually expressed in colony
1.10 Efficacy of a disinfection cycle or reprocessing cycle, forming units, cfu) and type (genus and species) of viable
or any part thereof, may be determined by comparison of the microorganisms used to contaminate a given sample or object.
number of microorganisms recovered from the control instru- Strain identification and the means used to identify the organ-
ment (initial recoverable control count) to the recovery deter- ism should be indicated.
mined for the test instruments. 3.2 Definitions of Terms Specific to This Standard:
1.11 A knowledge of microbiological techniques is required 3.2.1 accessible site, n—a location on or in a reusable
to conduct these procedures. medical instruments that can be contacted by bioburden and
1.12 This standard does not purport to address all of the disinfectants.
safety concerns, if any, associated with its use. It is the 3.2.2 reusable medical device, n—any medical instrument
responsibility of the user of this standard to establish appro- that is claimed at manufacture to be usable after reprocessing.
priate safety and health practices and determine the applica- 3.2.3 worst-case, n—the intentional exaggeration of one or
bility of regulatory limitations prior to use. more parameters of test compared to normal condition.
4. Summary of Test Method
2. Referenced Documents
4.1 This test method is performed by contamination of
2.1 ASTM Standards:
accessible, interior, and exterior surfaces of instruments or
E 1054 Practices for Evaluating Inactivators of Antimicro-
devices intending to reach the sites identified as the leastac-
bial Agents Used in Disinfectant, Sanitizer, Antiseptic, or
cessible or most difficult to reach sites.
Preserved Products
4.2 The number of microorganisms contaminating the test
3. Terminology instruments or devices prior to processing is determined by
contamination and elution of at least two control unprocessed
3.1 Definitions:
units (representing a large complex instrument). More control
3.1.1 bioburden, n—the number and type of viable micro-
units of smaller instruments may be used. Contamination with
organisms that can be recovered from surfaces using standard
an inoculum with high numbers of microorganisms to achieve
recovery procedures.
at least 10 cfu/instrument, recoverable is required.
3.1.2 CFU—colony forming units.
4.3 After inoculation, the test instrument(s) are processed
according to the manufacturer’s instructions for use of the
reprocessing cycle, the disinfectant, or disinfector. Either the
CDC-NIH Biosafety in Microbiological and Biomedical Laboratories, 3rd ed.,
disinfectant, disinfector cycle alone, or the disinfectant (disin-
U.S. Department of Health and Human Services, Washington, DC, 1993.
Annual Book of ASTM Standards, Vol 11.05. fector) cycle plus any cleaning, rinsing, or other contributory
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 1837
steps in the directions for use, may be tested. 7.1.6 Mycophil or Potato Dextrose Agar, with and without
4.4 Following processing, the test instruments are sampled appropriate neutralizers in 10 to 500-mL tubes or bottles
using specified elution and culture techniques to determine the tempered to 50 6 1°C (for fungi). Soybean-Casein Digest
number of surviving bacteria in colony forming units (cfu). Broth or agar, or both, may be used for many fungi.
7.1.7 Bacteria-Free Water (when a water rinse step is part
5. Significance and Use
of the reprocessing procedures).
5.1 This test method is designed to demonstrate and docu- 7.2 Test Organisms—Suspensions of selected test organ-
ment that reusable devices and medical instruments can be
isms, appropriate for test.
disinfected using a specified technique.
NOTE 1—Strains such as those identified in AOAC disinfectant test
5.2 This test method can be used to verify claims of
procedures or other publications or resistant environmental isolates that
disinfection of recesses, hinged sites, lumina, or other difficult-
have demonstrated resistance to antimicrobials should be selected.
to-reprocess areas of reusable medical devices and instruments.
7.2.1 Bacterial cultures are incubated until they reach at
5.3 This test method also can be used to document the
least 1 3 10 cfu/mL. For most test strains, this can be
contribution of each element of the reprocessing cycle for
achieved with a 48-h suspension of bacterial vegetative cells of
reusable medical devices and instruments.
test strains prepared in tubes or flasks of appropriate media and
5.4 The number of surviving bacteria may be assessed using
incubated at the appropriate optimal growth temperature,
swabbing and irrigation or total immersion.
62°C. Strains of mycobacteria are slow growing and must be
5.5 This test method may be used to produce quantitative or
incubated for longer times depending on the strain. M. terrae is
qualitative results.
normally countable using magnification and lateral lighting in
21 days, although it may be counted as early as 14 days.
6. Apparatus
7.2.2 Any test strain which is easy to identify, such as
6.1 Syringes, 10 to 50 mL, sterile.
Serratia marcescens, Escherichia coli, Mycobacterium bovis
6.2 Sterile Cotton, dacron or other swabs.
or Mycobacterium terrae, Pseudomonas aeruginosa, or Sta-
6.3 Sterile Petri Dishes.
phylococcus aureus, and has documented disinfectant resis-
6.4 Sterile Tubes, to hold 10 mL.
tance selected. Suspensions should be grown for sufficient time
6.5 Sterile Bottles, to hold 50 mL and sterile flasks to hold
to achieve a 10 -cfu/mL level.
250 to 500 mL.
7.3 Neutralizers (appropriate for test system)—For neutral-
6.6 Steam, or other type of sterilizer.
izer selection and testing refer to Practice E 1054. Neutralizers
6.7 Water Bath, to maintain temperatures from 20 to 50 6
may be added to dilution fluids.
2°C.
6.8 Incubator(s), to maintain 35 6 2°C.
8. Procedure
6.9 Membrane Filters and Filter Supports, for membrane
8.1 Use pre-cleaned and pre-sterilized or pre-disinfected
filters.
instruments or devices.
6.10 Colony Counter.
8.2 Inoculation of Devices (Endoscopes or Other Reusable
6.11 Disposable Plastic Pipettes, various sizes.
Instruments):
6.12 Medical Devices or Instruments, cleaned in accordance
with the manufacturer’s direction and sterilized or disinfected 8.2.1 The suspensions are used as grown for inoculation.
The approximate count may be estimated spectrophotometri-
(high level) prior to use.
6.13 Devices or Apparatus Specified by the Instrument, cally or by using routine plating procedures with appropriate
agar media. This is recommended to check that
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