ASTM E1837-96(2007)
(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 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 recovered from the control instrument (initial recoverable control count) to the recovery determined for the test instruments.
1.11 A knowledge of microbiological techniques is required to conduct these procedures.
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: E1837 − 96(Reapproved 2007)
Standard Test Method to
Determine Efficacy of Disinfection Processes for Reusable
Medical Devices (Simulated Use Test)
This standard is issued under the fixed designation E1837; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) 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
channelsofdevices,suchasendoscopes)withaterminalalcoholrinseratherthanexaminingonlythe
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.
Whenthisprocedureisperformedwitharepresentativemycobacterialculture,itisnecessarytouse
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 (1-5).
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-
ing reusable medical devices when it is tested with a challenge
1.2 This test method is designed to provide a reproducible
of vegetative cells including mycobacteria. Disinfection nor-
procedure to verify the effectiveness of a previously validated
mally deals with testing activity against vegetative cells of
disinfectant or disinfection procedure for reusable medical
instruments and devices.
This test method is under the jurisdiction of ASTM Committee E35 on
1.3 Thistestmethodisnotmeanttodefinetheeffectiveness
Pesticides, Antimicrobials, and Alternative Control Agents and is the direct
oforvalidationoftheparticulardisinfectionprocessusedorits
responsibility of Subcommittee E35.15 on Antimicrobial Agents.
Current edition approved Nov. 1, 2007. Published November 2007. Originally
kinetics, but rather, it is devised to confirm the effectiveness of
approved in 1996. Last previous edition approved in 1996 as E1837–96 (2002).
the disinfection process by simulating use situations with a
DOI: 10.1520/E1837-96R07.
2 particular test process using medical devices and instruments.
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard. Either manual or machine reprocessing can be tested.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1837 − 96 (2007)
1.4 This test method is intended for use with reusable 2. Referenced Documents
cleaned and previously sterilized or disinfected (high level) 4
2.1 ASTM Standards:
medical instruments and devices. Endoscopes are described in
E1054Test Methods for Evaluation of Inactivators of Anti-
thistestmethodasaworst-caseexampleforcontaminationand
microbial Agents
sampling. The selected sterilization or disinfection processes,
or both, should have been validated previously, as well as the 3. Terminology
effectiveness of rinsing for residual sterilant/disinfectant re-
3.1 Definitions:
moval determined.
3.1.1 bioburden, n—the number and type of viable micro-
organisms that can be recovered from surfaces using standard
1.5 An inoculum with high numbers of selected microor-
recovery procedures.
ganisms is applied to both test and control, cleaned and
sterilized, or disinfected medical instruments. Strains of mi-
3.1.2 CFU—colony forming units.
croorganisms with a recorded resistance to disinfectants are
3.1.3 disinfectant—anybiocidalchemicalthatproducesma-
usedtocontaminatetheinstrumentsitesknownorsuspectedto
terials free from vegetative microorganisms that may contami-
be the most difficult to reprocess.
nate them and potentially cause infection.
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.Otherdefinitionsdescribetheactionasapplicationof
complexity, size, difficulty in long-term incubation, or deteri-
aprocessresultingineliminationofmicroorganisms.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—Aseries 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,
drying.
vegetative bacteria, fungi including asexual spores, and lipid
1.8 A testing procedure can be performed on a complete and non-lipid viruses.
reprocessing cycle or can be limited to just the cleaning or (3) Low-level disinfection inactivate vegetative bacteria,
most fungi, and lipid viruses.
disinfection portions of the cycle whether reprocessing is done
in a machine or manually.
3.1.4 disinfector, n—any device or physical process that
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-
ments.
3.1.5 inoculum—the number (usually expressed in colony
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 Aknowledgeofmicrobiologicaltechniquesisrequired
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.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
CDC-NIH Biosafety in Microbiological and Biomedical Laboratories, 3rd ed., Standards volume information, refer to the standard’s Document Summary page on
U.S. Department of Health and Human Services, Washington, DC, 1993. the ASTM website.
E1837 − 96 (2007)
4. Summary of Test Method 6.12 MedicalDevicesorInstruments,cleanedinaccordance
with the manufacturer’s direction and sterilized or disinfected
4.1 This test method is performed by contamination of
(high level) prior to use.
accessible, interior, and exterior surfaces of instruments or
devices intending to reach the sites identified as the leastac- 6.13 Devices or Apparatus Specified by the Instrument,
cessible or most difficult to reach sites. Disinfectant or Disinfector Manufacturer.
4.2 The number of microorganisms contaminating the test 6.14 Vortex Mixer or Sonicator, or Both.
instruments or devices prior to processing is determined by
7. Reagents
contamination and elution of at least two control unprocessed
units (representing a large complex instrument). More control
7.1 Media:
units of smaller instruments may be used. Contamination with 7.1.1 Sterile buffered elution fluid containing 0.1% Triton
an inoculum with high numbers of microorganisms to achieve
X-100 prepared in Type III or better ASTM water. Specific
at least 10 cfu/instrument, recoverable is required. neutralizers for the test disinfectant may be added.
7.1.2 Soybean-Casein Digest Broth, USP, with and without
4.3 After inoculation, the test instrument(s) are processed
appropriateneutralizersforthespecifictestdisinfectantchemi-
according to the manufacturer’s instructions for use of the
cal.
reprocessing cycle, the disinfectant, or disinfector. Either the
7.1.3 Soybean-Casein Digest Agar, USP, with and without
disinfectant, disinfector cycle alone, or the disinfectant (disin-
appropriate neutralizers in 10 to 50-mL tubes or bottles
fector) cycle plus any cleaning, rinsing, or other contributory
tempered to 50 6 10°C.
steps in the directions for use, may be tested.
7.1.4 Middlebrook 7H9 Broth, with and without appropriate
4.4 Following processing, the test instruments are sampled
neutralizers in 10 to 50-mL tubes or 250 to 500-mL flask (for
using specified elution and culture techniques to determine the
mycobacteria).
number of surviving bacteria in colony forming units (cfu).
7.1.5 Middlebrook 7H11 Agar,withandwithoutappropriate
neutralizersin10to500-mLtubesorbottlestemperedto50 6
5. Significance and Use
1°C (for Mycobacteria ).
5.1 This test method is designed to demonstrate and docu-
7.1.6 Mycophil or Potato Dextrose Agar, with and without
ment that reusable devices and medical instruments can be
appropriate neutralizers in 10 to 500-mL tubes or bottles
disinfected using a specified technique.
tempered to 50 6 1°C (for fungi). Soybean-Casein Digest
Broth or agar, or both, may be used for many fungi.
5.2 This test method can be used to verify claims of
7.1.7 Bacteria-FreeWater(whenawaterrinsestepispartof
disinfectionofrecesses,hingedsites,lumina,orotherdifficult-
the reprocessing procedures).
to-reprocessareasofreusablemedicaldevicesandinstruments.
7.2 Test Organisms—Suspensions of selected test organ-
5.3 This test method also can be used to document the
isms, appropriate for test.
contribution of each element of the reprocessing cycle for
reusable medical devices and instruments.
NOTE 1—Strains such as those identified in AOAC disinfectant test
procedures or other publications or resistant environmental isolates that
5.4 Thenumberofsurvivingbacteriamaybeassessedusing
have demonstrated resistance to antimicrobials should be selected.
swabbing and irrigation or total immersion.
7.2.1 Bacterial cultures are incubated until they reach at
5.5 Thistestmethodmaybeusedtoproducequantitativeor 8
least1×10 cfu/mL.Formostteststrains,thiscanbeachieved
qualitative results.
with a 48-h suspension of bacterial vegetative cells of test
strains prepared in tubes or flasks of appropriate media and
6. Apparatus
incubated at the appropriate optimal growth temperature,
6.1 Syringes, 10 to 50 mL, sterile.
62°C. Strains of mycobacteria are slow growing and must be
incubatedforlongertimesdependingonthestrain. M. terraeis
6.2 Sterile Cotton, dacron or other swabs.
normally countable using magnification and lateral lighting in
6.3 Sterile Petri Dishes.
21 days, although it may be counted as early as 14 days.
6.4 Sterile Tubes, to hold 10 mL.
7.2.2 Any test strain which is easy to identify, such as
Serratia marcescens, Escherichia coli, Mycobacterium bovis
6.5 Sterile Bottles, to hold 50 mL and sterile flasks to hold
or Mycobacterium terrae, Pseudomonas aeruginosa, or
250 to 500 mL.
Staphylococcus aureus,andhasdocumenteddisinfectantresis-
6.6 Steam, or other type of sterilizer.
tanceselected.Suspensionsshouldbegrownforsufficienttime
6.7 Water Bath, to maintain temperatures from 20 to 50 6 to achieve a 10 -cfu/mL level.
2°C.
7.3 Neutralizers (appropriate for test system)—For neutral-
6.8 Incubator(s), to maintain 35 6 2°C. izer selection and testing refer to Practice E1054. Neu
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