ASTM E2922-23

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2922 − 15 E2922 − 23
Standard Guide for
The Use of Standard Test Methods and Practices for
Evaluating Antibacterial Activity on Textiles
This standard is issued under the fixed designation E2922; 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
1.1 This guide provides users with an index of procedures in the form of test methods, practices, and related international
documents that are currently used in the textile industry for determining antibacterial properties of antimicrobial treated textile
articles. This guide is not considered as all-inclusive for antimicrobial testing procedures related to textiles.
1.2 This guide identifies some existing ASTM and other industry standard test methods applicable for testing the antibacterial
performance on textiles and discusses options within each method that have been used to address specific end-use performance
expectations.expectations in addition to measuring wash durability of such activity.
1.3 This guide is intended to assist testing facilities in determining which test methods are appropriate for which treated articles
based on type of antimicrobial active involved (diffusible versus non-diffusible), nature of test fabric, and expected end use.
1.4 The test methods indicated in this guide should be performed only by those trained in microbiological techniques, are familiar
with textile antimicrobial agents and with the end use exposures of the antimicrobial treated textile material.
1.5 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 healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E2149 Test Method for Determining the Antimicrobial Activity of Antimicrobial Agents Under Dynamic Contact Conditions
E2180 Test Method for Determining the Activity of Incorporated Antimicrobial Agent(s) In Polymeric or Hydrophobic Materials
E2722 Test Method for Using Seeded-Agar for the Screening Assessment of Antimicrobial Activity in Fabric and Air Filter
Media (Withdrawn 2022)
E2756 Terminology Relating to Antimicrobial and Antiviral Agents
E3160 Test Method for Quantitative Evaluation of the Antibacterial Properties of Porous Antibacterial Treated Articles
This guide is under the jurisdiction of ASTM Committee E35 on Pesticides, Antimicrobials, and Alternative Control Agents and is the direct responsibility of
Subcommittee E35.15 on Antimicrobial Agents.
Current edition approved May 1, 2015April 1, 2023. Published June 2015April 2023. Originally approved in 2015. Last previous edition approved in 2015 as E2922 – 15.
DOI: 10.1520/E2922–1510.1520/E2922-23.
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 Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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E3162 Practice Measuring the Durability of Antibacterial Agents Applied to Textiles under Simulated Home Laundering
Conditions
2.2 AATCC Standards:
AATCC Test Method 61: Test Method for Colorfastness to Laundering: Accelerated. American Association of Textile Chemists
and Colorists, RTP, NC
AATCC Test Method 90: Antibacterial Activity Assessment of Textile Materials: Agar Plate Method. American Association of
Textile Chemists and Colorists, RTP, NC
AATCC Test Method 100: Antibacterial Finishes on Fabrics, Evaluation of. American Association of Textile Chemists and
Colorists, RTP, NC
AATCC Test Method 147: Antibacterial Activity Assessment of Textile Materials: Parallel Streak Method. American
Association of Textile Chemists and Colorists, RTP, NC
AATCC Test Method 211: Reduction of Bacterial Odor on Antibacterial Treated Textiles. American Association of Textile
Chemists and Colorists, RTP, NC
2.3 ISO Standards:
ISO 20743 Textiles – Determination of Antibacterial Activity of Antibacterial Finished Products
ISO 22196 Plastics – Measurement of Antibacterial Activity on Plastics Surfaces
2.4 JIS Standards:
JIS L 1902 Testing for Antibacterial Activity and Efficacy on Textile Products
JIS Z 2801 Antimicrobial Products – Test for Antimicrobial Activity and Efficacy
2.5 Other Standards:
SNV 195920 Examination of the Antimicrobial Effect of Impregnated Textiles by the Agar Diffusion Test
IBRG TEX13/005/1.0 Quantitative Method for Evaluating Bactericidal Activity of Textiles and Porous Materials and Articles
IACM 0600 Standard Operating Procedure for Rapid Sample Rinse
3. Terminology
3.1 For definitions of terms used in this Guideguide see Terminology E2756.
4. Significance and Use
4.1 Antimicrobial agents are routinely used for treating textile materials for the reduction of biodeterioration and bacterial odor
generation. Furthermore, textiles are treated to prevent or limit microbial cross-contamination in healthcare settings.
4.2 Antimicrobial agents used in textiles will vary with regard to their broad-spectrum effectiveness, biostatic/biocidal properties,
and binding properties in or on particular substrates. When selecting antibacterial test methods as the sole means to predict end
use behavior it is critical to understand the intended end use conditions of the treated articles.
4.3 Textile materials differ with regard to the knit/weave, fabric composition, and added functional feature (for example, water
repellent, flame retardant, softener, whitener). Each of these factors may alter test results within a given method.
4.4 The test methods indicated below differ mainly in the procedure for inoculating samples, levels of nutrients in the bacterial
challenge, organisms used, and exposure times.exposure times, and procedure for sterilization of test samples. Each of these
parameters are often subject to industry modifications.
4.5 Some antimicrobial treated articles are not suitable for sterilization due to the sensitivity of these antimicrobial agents to high
temperature and humidity. Furthermore, some antimicrobial agents may be unrealistically activated due to UV sterilization which
could show false positive antimicrobial properties. Sterilization of test fabrics prior to testing should be avoided if possible. All
modifications of the methods indicated below should be clearly indicated on associated test reports and should be appropriate to
the antimicrobial technology used.
Available from AATCC 1 Davis Dr Research Triangle Park, NC 27709-2215 USA. http://www.aatcc.org/
Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org.
Available from Japanese Industrial Standards Committee (JIS) 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo 100-8901, JAPAN. http://www.jisc.go.jp
Available from the International Biodeterioration Research Group (IBRG), Pale Lane, Hartley Wintney, Hants, UK RG27 8DH. http://www.ibrg.org.
Available from the International Antimicrobial Council (IAC), 2298 N. Eastman, Midland, MI 48642 USA. http://www.amcouncil.org.
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4.6 This guide is intended to review each commonly used industry standard test methodstandard for its applicability with an
understanding of each of the factors listed above. Further, it is the intention of this guide to indicate commonly used and generally
accepted modifications of each methodstandard when measuring specific end-use functionalities.
4.7 These test methodsstandards are not, in themselves, absolute indicators of real life performance. Such performance criteria are
developed based on a series of antimicrobial and analytical test methods in addition to simulated real life use studies. All
antimicrobial agents used for the treatment of textiles should be compliant with local regulatory agencies and should be deemed
safe for the proposed end-use and claims.
5. Qualitative Antimicrobial Test Methods for Textiles
5.1 AATCC TM 147—is a qualitative test to measure antibacterial activity of diffusible antimicrobial agents on treated textile
material.
5.1.1 Significance and Use—The objective is to detect bacteriostatic activity on textile materials. The method is useful for
obtaining a rough estimate of activity in that the growth of the inoculum organism decreases from one end of each streak to the
other and from one streak to the next resulting in increasing degrees of sensitivity. The size of the zone of inhibition and the
narrowing of the streaks caused by the presence of the antibacterial agent permit an estimate of the residual antibacterial activity
after multiple washes.
5.1.2 Typical industry modifications include the use of multiple microbial organisms on a single plate. While the test method was
developed to obtain a rough estimate of activity of a treated article by systematically decreasing the dose of organism across the
surface of an agar plate, so too can this method be used as a fast determination of broad spectrum activity if multiple organisms
are used. In many cases, four organisms are streaked lengthwise per agar plate (Escherichia coli,Klebsiella pneumoniae,
Staphylococcus aureus,Candida albicans) with a test fabric strip placed at 90 degrees 90° on the agar surface across streaks if
multiple organisms are used. In many cases, four organisms are streaked lengthwise per agar plate (Escherichia coli,Klebsiella
pneumoniae,Staphylococcus aureus,Candida albicans) with a test fabric strip placed at 90 degrees 90° on the agar surface across
streaks.
5.1.3 Evaluation of the test includes determinationTest includes Determination of a Zone of Inhibition (ZOI)—theThe width of the
inhibition zone away from the treated substrate (in millimetres) or an evaluation of the level of growth underneath the test substrate.
Care must be taken when evaluating growth directly underneath the sample. Some materials, including plastics and films, can make
such intimate contact with the agar surface that no microbial growth is observed underneath the sample. It is recommended to
compare results of treated samples to an untreated sample composed of the same type of material to avoid false positives.
5.1.4 Lack of a ZOI does not necessarily indicate that the treated material does not contain an antimicrobial agent. In some cases,
the nutrients available in agar medium or the agar matrix itself can deactivate the antimicrobial agent, leading to false-negative
results. Alternative methods such as the Test Method E2149 or the AATCC Test Method E3160/AATCC 100 with low to no nutrient
inoculum conditions can better define activity for those antimicrobials that are bound by nutrients or agar.
5.1.5 Growth directly under a test fabric does not necessarily indicate that the treated material does not contain an antimicrobial
agent. If direct contact with the treated textile is required, bacteria may grow directly under the treated substrate without the needed
intimate contact with the treated substrate. Alternative quantitative methods indicated below may be more appropriate for
antimicrobial agents that are not diffusible into the surrounding medium.
5.1.6 Many test methods incorporate the agar based methodology for determining ZOI activity. AATCC TM 90, SNV 195920 and
JIS L1902 L 1902 are examples of international standards that contain aspects of measuring zone of inhibition in an agar medium.
5.1.7 This test method can be a good bioassay method for detecting antimicrobial activity compared to untreated controls and is
appropriate for use in quality control test programs.
5.2 Test Method E2722—is designed to evaluate qualitatively the presence of antibacterial and antifungal activity in or on fabrics
or air filter media.
5.2.1 Significance and Use—This test method provides for rapid screening of antimicrobial treatments located in or on fabrics and
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air filter media. The method simulates actual use conditions that may occur on fabrics and provides a means to screen for activity
and durability of an antimicrobial treatment under conditions of organic loading.
5.2.2 Typical industry modifications include the use of multiple microbial organisms.
5.2.3 This test method provides for a simultaneous assessment of multiple fabric components for antimicrobial activity, for
example, fabric, component fibers with polymer incorporated treatments, and back coating if present.
5.2.4 This test method may not be suited for covalently bonded (non-soluble or non-leaching) antimicrobials such as
silane-modified quaternary ammonium compounds or antimicrobials with limited migration through nutrient agar.
5.2.5 Growth next to a test fabric does not necessarily indicate that the treated material does not contain an antimicrobial agent.
If direct contact with the treated textile or some migration of the antimicrobial agent into the nutrient agar is required, bacteria may
grow next to the test material without the needed intimate contact with the treated substrate. Alternative quantitative methods
indicated below may be more appropriate for antimicrobial agents that are not readily diffusible into the surrounding medium.
5.2.6 This test method can be a good bioassay method for detecting antimicrobial activity compared to untreated controls and is
appropriate for use in quality control test programs.
6. Quantitative Antimicrobial Test Methods for Textiles
6.1 AATCC TM 100—is designed to measure the antimicrobial activity of textiles after direct inoculation of the textile surface.
6.1.1 Significance and Use—This test method provides a quantitative procedure for the comparison and evaluation of the degree
of antibacterial activity after a 24 h exposure to the test bacteria on the test fabric. After exposure, the bacterial challenge is eluted
from the swatches and enumerated. The percent reduction of bacteria of the test fabric after 24 h versus the initial inoculum (that
is, recovery at Time 0) or a relative untreated control after identical contact time is calculated.
6.1.2 This method was originally is written to provide a 24 h contact of the bacteria with the treated surfaces. Increased and
decreased times may be used if accompanied by appropriate control fabrics to ensure the survival of the organism on the surface
without treatment.
6.1.3 Although the current method appears to indicate that the bacteriaThis original method indicated that the bacterial inocula
should be prepared in full-strength nutrient broth, the broth. In the most recent update (2019), the levels of nutrients in this test
often are modified to have been changed to specify a dilute nutrient solution (for example, 1:20 or 1:500 dilution of full-strength
Nutrient Broth) or a non-nutrient solution such as water, saline or phosphate buffer. (1:20 full-strength Nutrient Broth). Diluted
nutrient solutions have been shown to promote slight to moderate microbial growth over the 24 h contact time. It is recommended
to include the inoculum carrier solution that was utilized in the test in the test report to allow readers to compare results among
different test labs.time on a specified viability control fabric while not significantly affecting the antimicrobial additive on/in the
fabric.
6.1.4 The method often requires modification for testing of hydrophobic samples. Options include suspending the bacteria in a
dilute agar slurry or the the use of plastic films or cover slips to promote more intimate contact of the inoculum to the treated
surface on non-absorbent or highly hydrophobic surfaces. This modification creates methodology similar to the ISO 22196 test
method.and JIS Z2801 test methods.
6.1.5 The use of neutralizers in the recovery broth is essential in order to deactivate any remaining antimicrobial agents which may
carry over in the dilution tubes. The neutralizer should be selected based on its performance against the antimicrobial agent in
question.
6.1.6 This test method is a good bioassay method for detecting biocidal activity compared to the initial inoculum (Time 0) or
biostatic activity compared to an untreated control and is appropriate for use in quality control test programs.
6.1.7 This test method includes the use of both Gram positive bacteria (Staphylococcus aureus) and Gram negative bacteria. While
the Gram negative Klebsiella pneumoniae is specified, many laboratories will substitute the Gram negative Escherichia coli as it
has been shown to provide better repeatability. A standard industrial practice is to combine both Gram positive and Gram negative
organisms into a single mixed inoculum. Retrieval on selective media has been shown to be effective at identifying both organisms
while not affecting the overall antimicrobial reduction levels.
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6.1.8 This test method requires the addition of an untreated Viability Control Fabric (VCF) to ensure that conditions are met that
will provide microbial growth if possible. The VCF must demonstrate at least 1.5 log bacterial growth over the 24 h contact period
under the parameters outlined in the method.
6.1.9 Sterilization of textile samples using steam autoclaving prior to microbiological testing can eliminate any inherent
contamination on the sample, but also may alter the antimicrobial agent, resulting in either false positive or false negative results.
It is recommended to avoid steam sterilization of samples unless absolutely necessary.If sterilization is performed, the method and
reason for sterilization must be noted on the test report.
6.2 AATCC TM 211—is designed to measure the antimicrobial and anti-odor activity of textiles after direct inoculation of the
textile surface with specific surrogate organisms and nutrient solution and subsequently measuring the ammonia generated due to
the bioconversion of urea to ammonia using a volatiles detection system.
6.2.1 Significance and Use—This test method provides a quantitative procedure for the comparison and evaluation of the degree
of bacterial odor generation after a 20 6 2 h exposure to the test bacteria on treated and untreated test fabric. Lower incubation
times (6 to 8 h) have also been used and have been shown to effectively demonstrate anti-odor properties on antimicrobial treated
textiles. This method is designed to measure the microbial generation of ammonia due to the bioconversion of urea using simple,
inexpensive gas detection tubes.
6.2.2 This method is written to provide direct contact between specific ammonia generating bacteria and textiles treated and
untreated with antimicrobial agents.
6.2.3 Specific ammonia generating organisms are employed as surrogate test organisms, taking advantage of the species’ ability
to produce ammonia while metabolizing urea or other protein residues. Ammonia is typically identified as a problem odor on
textiles. Generation of ammonia on untreated textiles is a general indication of the presence of actively metabolizing bacteria.
Likewise, lack of (or reduced) ammonia generation compared directly to an identical untreated control fabric, indicate the control
of bacterial metabolism on a treated textile surface.
6.2.4 The test method includes the use of the Gram positive bacteria Staphylococcus saprophyticus and the Gram negative bacteria
Proteus vulgaris. These organisms were selected due to their ability to produce ammonia under these defined test conditions. Other
bacteria that can produce a metabolic by-product which can be measured using a different Drager Tube may be used but these
variations must be reported and recognized as a modification of this test method.
6.2.5 This test method does not directly measure biocidal activity on a treated textile but rather is predictive of biostatic properties
provided by the addition of an antimicrobial agent.
6.2.6 This test method requires the addition of an untreated Viability Control Fabric (VCF) to ensure that conditions are met that
will provide microbial growth if possible. The VCF should exceed the 1500 ppm ammonia limit on the Drager tubes within the
8 h incubation period.
6.2.7 Sterilization of textile samples using steam autoclaving prior to microbiological testing can eliminate any inherent
contamination on the sample, but also may alter the antimicrobial agent, resulting in either false positive or false negative results.
If sterilization is performed, the method and reason for sterilization must be noted on the test report.
6.3 Test Method E2149—is designed to measure the antimicrobial activity of non-diffusible antimicrobial agents.
6.3.1 Significance and Use—Immobilized (cross-linked) antimicrobial agents are not free to diffuse into their environment under
normal conditions of use. Textile methods, such as AATCC TM 147, that are directly dependent on
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