ASTM E1837-96(2002)
(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)
SIGNIFICANCE AND USE
This test method is designed to demonstrate and document that reusable devices and medical instruments can be disinfected using a specified technique.
This test method can be used to verify claims of disinfection of recesses, hinged sites, lumina, or other difficult-to-reprocess areas of reusable medical devices and instruments.
This test method also can be used to document the contribution of each element of the reprocessing cycle for reusable medical devices and instruments.
The number of surviving bacteria may be assessed using swabbing and irrigation or total immersion.
This test method may be used to produce quantitative or qualitative results.
SCOPE
1.1 This test method is intended to describe a procedure for testing the effectiveness of a disinfection process for reprocessing reusable 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. Endoscopes are described in 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 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 devices, 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 ...
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Designation:E1837–96 (Reapproved 2002)
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
orhardwatermineralsasaninorganicloadcanbemadetoenhanceworst-caseconditions.Whenthese
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,includingcleaning,rinsing,anddisinfection(includingoptionaltreatmentoftheinternal
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
havebeenrecordedwithvegetativecellsofbacteria,forexample,Pseudomonasandthemycobacteria.
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 bacteria, viruses, and fungi. Since this test method is process
oriented, the user may wish to examine a variety of test
1.1 This test method is intended to describe a procedure for
organisms.
testingtheeffectivenessofadisinfectionprocessforreprocess-
1.2 This test method is designed to provide a reproducible
ing reusable medical devices when it is tested with a challenge
procedure to verify the effectiveness of a previously validated
of vegetative cells including mycobacteria. Disinfection nor-
disinfectant or disinfection procedure for reusable medical
mally deals with testing activity against vegetative cells of
instruments and devices.
1.3 This test method is not meant to define the effectiveness
This test method is under the jurisdiction of ASTM Committee E35 on oforvalidationoftheparticulardisinfectionprocessusedorits
Pesticides and Alternative Control Agents and is the direct responsibility of
kinetics, but rather, it is devised to confirm the effectiveness of
Subcommittee E35.15 on Antimicrobial Agents.
the disinfection process by simulating use situations with a
Current edition approved Oct. 10, 2002. Published March 2003. Originally
particular test process using medical devices and instruments.
approved in 1996. Last previous edition approved in 1996 as E 1837 – 96.
The boldface numbers in parentheses refer to the list of references at the end of
Either manual or machine reprocessing can be tested.
this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1837–96 (2002)
1.4 This test method is intended for use with reusable bial Agents Used in Disinfectant, Sanitizer, Antiseptic, or
cleaned and previously sterilized or disinfected (high level) Preserved Products
medical instruments and devices. Endoscopes are described in
3. Terminology
thistestmethodasaworst-caseexampleforcontaminationand
sampling. The selected sterilization or disinfection processes, 3.1 Definitions:
or both, should have been validated previously, as well as the 3.1.1 bioburden, n—the number and type of viable micro-
effectiveness of rinsing for residual sterilant/disinfectant re- organisms that can be recovered from surfaces using standard
moval determined. recovery procedures.
1.5 An inoculum with high numbers of selected microor- 3.1.2 CFU—colony forming units.
ganisms is applied to both test and control, cleaned and 3.1.3 disinfectant—anybiocidalchemicalthatproducesma-
sterilized, or disinfected medical instruments. Strains of mi- terials free from vegetative microorganisms that may contami-
croorganisms with a recorded resistance to disinfectants are nate them and potentially cause infection.
used to contaminate the instrument sites known or suspected to 3.1.3.1 Discussion—The definitions included are the tradi-
be the most difficult to reprocess. tional ones. The user may choose to conform to other criteria
1.6 It is impractical to test for recovery of survivors by that specify elimination of a certain number of test microor-
immersion of some instruments, for example, endoscopes or ganisms. Other definitions describe the action as application of
some laproscopic instruments, in growth medium because of aprocessresultingineliminationofmicroorganisms.Whatever
complexity, size, difficulty in long-term incubation, or deteri- criteria is selected, it should be stated before initiation of the
ous effects resulting from incubation. Elution of organisms test procedure.
from the inoculated surfaces, therefore, may be performed to 3.1.3.2 Discussion—Aseries of three definitions devised by
estimate the number of recoverable organisms. Immersion can Spaulding (6, 8) separated the activity of germicides against
be used for smaller instruments. spores and mycobacteria and non-lipid viruses and are there-
1.7 Control instruments are inoculated in the same manner fore defined by activity against groups of microorganisms.
as the test instruments and elution or immersion methods are These definitions are as follows:
performed to determine the number of organisms recoverable (1) High-level disinfectants must inactivate bacteria en-
from the instrument. For channeled devices, such as endo- dospores, mycobacteria, non-lipid viruses, fungi, vegetative
scopes testing, the number of organisms recoverable from the bacteria, and lipid viruses. If exposure time is extended long
instrument (inside and outside) will serve as the initial control enough, this type of germicide can be used as a sterilant.
count. It is expected that some fraction of the number of (2) Medium-level disinfectants inactivate mycobacteria,
organisms inoculated will be lost in the process of inoculation/ vegetative bacteria, fungi including asexual spores, and lipid
drying. and non-lipid viruses.
1.8 A testing procedure can be performed on a complete (3) Low-level disinfection inactivate vegetative bacteria,
reprocessing cycle or can be limited to just the cleaning or most fungi, and lipid viruses.
disinfection portions of the cycle whether reprocessing is done 3.1.4 disinfector, n—any device or physical process that
in a machine or manually. provides a biocidal process that produces materials free from
1.9 After the test cycle has been completed, remaining vegetative microorganisms that may contaminate them and
inoculated bacteria will be recovered from test instruments potentially cause infection.
using the same elution procedures as for the control instru- 3.1.5 inoculum—the number (usually expressed in colony
ments. forming units, cfu) and type (genus and species) of viable
1.10 Efficacy of a disinfection cycle or reprocessing cycle, microorganisms used to contaminate a given sample or object.
or any part thereof, may be determined by comparison of the Strain identification and the means used to identify the organ-
number of microorganisms recovered from the control instru- ism should be indicated.
ment (initial recoverable control count) to the recovery deter- 3.2 Definitions of Terms Specific to This Standard:
mined for the test instruments. 3.2.1 accessible site, n—a location on or in a reusable
1.11 Aknowledge of microbiological techniques is required medical instruments that can be contacted by bioburden and
to conduct these procedures. disinfectants.
1.12 This standard does not purport to address all of the 3.2.2 reusable medical device, n—any medical instrument
safety concerns, if any, associated with its use. It is the that is claimed at manufacture to be usable after reprocessing.
responsibility of the user of this standard to establish appro- 3.2.3 worst-case, n—the intentional exaggeration of one or
priate safety and health practices and determine the applica- more parameters of test compared to normal condition.
bility of regulatory limitations prior to use.
4. Summary of Test Method
2. Referenced Documents
4.1 This test method is performed by contamination of
accessible, interior, and exterior surfaces of instruments or
2.1 ASTM Standards:
devices intending to reach the sites identified as the leastac-
E 1054 Practices for Evaluating Inactivators of Antimicro-
cessible or most difficult to reach sites.
CDC-NIH Biosafety in Microbiological and Biomedical Laboratories, 3rd ed.,
U.S. Department of Health and Human Services, Washington, DC, 1993. Discontinued. See 1999 Annual Book of ASTM Standards, Vol 11.05.
E1837–96 (2002)
4.2 The number of microorganisms contaminating the test 7.1.2 Soybean-Casein Digest Broth, USP, with and without
instruments or devices prior to processing is determined by appropriate neutralizers for the specific test disinfectant chemi-
contamination and elution of at least two control unprocessed cal.
units (representing a large complex instrument). More control 7.1.3 Soybean-Casein Digest Agar, USP, with and without
units of smaller instruments may be used. Contamination with appropriate neutralizers in 10 to 50-mL tubes or bottles
an inoculum with high numbers of microorganisms to achieve tempered to 50 6 10°C.
at least 10 cfu/instrument, recoverable is required. 7.1.4 Middlebrook 7H9 Broth, with and without appropriate
4.3 After inoculation, the test instrument(s) are processed neutralizers in 10 to 50-mL tubes or 250 to 500-mL flask (for
according to the manufacturer’s instructions for use of the mycobacteria).
reprocessing cycle, the disinfectant, or disinfector. Either the 7.1.5 Middlebrook 7H11Agar,withandwithoutappropriate
disinfectant, disinfector cycle alone, or the disinfectant (disin- neutralizers in 10 to 500-mLtubes or bottles tempered to 50 6
fector) cycle plus any cleaning, rinsing, or other contributory 1°C (for Mycobacteria).
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-reprocessareasofreusablemedicaldevicesandinstruments.
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 Thenumberofsurvivingbacteriamaybeassessedusing
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
incubatedforlongertimesdependingonthestrain. M. terraeis
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,cleanedinaccordance
8.2.1 The suspensions are used as grown for inoculation.
with the manufacturer’s directio
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