SIST EN ISO 11138-7:2019

Sterilization of health care products - Biological indicators - Part 7: Guidance for the selection, use and interpretation of results (ISO 11138-7:2019)

This document provides guidance for the selection, use and interpretation of results from application of biological indicators when used in the development, validation and routine monitoring of sterilization processes.
It does not consider those processes that rely solely on physical removal of microorganisms, e.g. filtration.
It is not applicable to combination processes using, for example, washer-disinfectors or flushing and steaming of pipelines.
It does not specify requirements for the selection and use of biological indicators intended to monitor vaporised hydrogen peroxide processes for isolator and room biodecontamination processes at atmospheric pressure.
It is not applicable to liquid immersion sterilization processes.

Sterilisation von Produkten für die Gesundheitsfürsorge - Biologische Indikatoren - Teil 7: Leitfaden für die Auswahl, Verwendung und Interpretation von Ergebnissen (ISO 11138-7:2019)

Dieses Dokument enthält einen Leitfaden für die Auswahl, Verwendung und Interpretation von Ergebnissen, die durch die Anwendung von biologischen Indikatoren bei der Entwicklung, Validierung und Routineüberwachung von Sterilisationsverfahren erzielt werden.
Es umfasst keine Verfahren, die ausschließlich auf physikalischer Entfernung von Mikroorganismen, z. B. durch Filtration, beruhen.
Es ist nicht auf Kombinationsverfahren anwendbar, die z. B. Reinigungs /Desinfektionsgeräte verwenden oder das Durchspülen und die Dampfbehandlung von Rohrleitungen.
Es legt keine Anforderungen an die Auswahl und Verwendung biologischer Indikatoren fest, die zur Über-wachung von Verfahren mit verdampftem Wasserstoffperoxid für die Biodekontamination von Isolatoren und Räumen unter Atmosphärendruck vorgesehen sind.
Es gilt nicht für Sterilisationsverfahren mit Flüssigkeitskapselung.

Stérilisation des produits de santé - Indicateurs biologiques - Partie 7: Directives générales pour la sélection, l’utilisation et l’interprétation des résultats (ISO 11138-7:2019)

Le présent document fournit des directives pour la sélection, l'utilisation et l'interprétation des résultats issus de l'application des indicateurs biologiques dans la mise au point, la validation et la surveillance de routine des procédés de stérilisation.
Il ne traite pas des procédés qui reposent uniquement sur l'élimination physique des microorganismes, par exemple la filtration.
Il n'est pas applicable aux procédés fonctionnant en combinaison avec, par exemple, des laveurs-désinfecteurs ou des machines de rinçage et traitement à la vapeur des canalisations.
Il ne spécifie pas les exigences relatives à la sélection et à l'utilisation des indicateurs biologiques destinés à surveiller les procédés au peroxyde d'hydrogène vaporisé pour les isolateurs et les procédés de biodécontamination des pièces à la pression atmosphérique.
Il n'est pas applicable aux procédés de stérilisation par immersion dans un liquide.

Sterilizacija izdelkov za zdravstveno nego - Biološki indikatorji - 7. del: Navodilo za izbiro, uporabo in predstavitev rezultatov (ISO 11138-7:2019)

Ta dokument podaja navodilo za izbiro, uporabo in predstavitev rezultatov pri uporabi bioloških indikatorjev, kadar se uporabljajo pri razvoju, potrjevanju in rutinskem spremljanju sterilizacijskih postopkov.
Ne upošteva tistih postopkov, ki temeljijo samo na fizičnem odstranjevanju mikroorganizmov, npr. filtriranju.
Ne uporablja se za kombinirane postopke, ki na primer uporabljajo čistilno-dezinfekcijske naprave ali spiranje in parno obdelavo cevovodov.
Ne določa zahtev za izbiro in uporabo bioloških indikatorjev, ki so namenjeni spremljanju postopkov z uplinjenim vodikovim peroksidom pri postopkih biološke dekontaminacije izolatorja in prostorov pri atmosferskem tlaku.
Ne uporablja se za postopke sterilizacije s potopitvijo v tekočino.

General Information

• Status: Published
• Public Enquiry End Date: 14-Nov-2017
• Publication Date: 03-Jun-2019
• ICS: 11.080.01 - Sterilization and disinfection in general
• Technical Committee: VAZ - Healthcare
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 09-May-2019
• Due Date: 14-Jul-2019
• Completion Date: 04-Jun-2019
• Directive: 93/42/EEC - Council Directive 93/42/EEC of 14 June 1993 concerning medical devices
• Ref Project: EN ISO 11138-7:2019 - Sterilization of health care products - Biological indicators - Part 7: Guidance for the selection, use and interpretation of results (ISO 11138-7:2019)

Relations

• Replaces: SIST EN ISO 14161:2010 - Sterilization of health care products - Biological indicators - Guidance for the selection, use and interpretation of results (ISO 14161:2009)
• Effective Date: 01-Jul-2019

Standards Content (Sample)

SLOVENSKI STANDARD
01-julij-2019
Nadomešča:
SIST EN ISO 14161:2010
Sterilizacija izdelkov za zdravstveno nego - Biološki indikatorji - 7. del: Navodilo za
izbiro, uporabo in predstavitev rezultatov (ISO 11138-7:2019)
Sterilization of health care products - Biological indicators - Part 7: Guidance for the
selection, use and interpretation of results (ISO 11138-7:2019)
Sterilisation von Produkten für die Gesundheitsfürsorge - Biologische Indikatoren - Teil 7:
Leitfaden für die Auswahl, Verwendung und Interpretation von Ergebnissen (ISO 11138-
7:2019)
Stérilisation des produits de santé - Indicateurs biologiques - Partie 7: Directives
générales pour la sélection, l’utilisation et l’interprétation des résultats (ISO 11138-
7:2019)
Ta slovenski standard je istoveten z: EN ISO 11138-7:2019
ICS:
11.080.01 Sterilizacija in dezinfekcija na Sterilization and disinfection
splošno in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 11138-7
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2019
EUROPÄISCHE NORM
ICS 11.080.01 Supersedes EN ISO 14161:2009
English Version
Sterilization of health care products - Biological indicators
- Part 7: Guidance for the selection, use and interpretation
of results (ISO 11138-7:2019)
Stérilisation des produits de santé - Indicateurs Sterilisation von Produkten für die
biologiques - Partie 7: Directives générales pour la Gesundheitsfürsorge - Biologische Indikatoren - Teil 7:
sélection, l'utilisation et l'interprétation des résultats Leitfaden für die Auswahl, Verwendung und
(ISO 11138-7:2019) Interpretation von Ergebnissen (ISO 11138-7:2019)
This European Standard was approved by CEN on 4 February 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11138-7:2019 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 11138-7:2019) has been prepared by Technical Committee ISO/TC 198
"Sterilization of health care products" in collaboration with Technical Committee CEN/TC 102
“Sterilizers and associated equipment for processing of medical devices” the secretariat of which is held
by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by October 2019, and conflicting national standards shall
be withdrawn at the latest by October 2019.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 14161:2009.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 11138-7:2019 has been approved by CEN as EN ISO 11138-7:2019 without any
modification.
INTERNATIONAL ISO
STANDARD 11138-7
First edition
2019-03
Sterilization of health care products —
Biological indicators —
Part 7:
Guidance for the selection, use and
interpretation of results
Stérilisation des produits de santé — Indicateurs biologiques —
Partie 7: Directives générales pour la sélection, l’utilisation et
l’interprétation des résultats
Reference number
ISO 11138-7:2019(E)
©
ISO 2019
ISO 11138-7:2019(E)
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

ISO 11138-7:2019(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 4
5 Characteristics of biological indicators . 6
5.1 General . 6
5.2 Test organism suspension for direct inoculation of products . 7
5.3 Inoculated carriers . 7
5.4 Self-contained biological indicators . 8
6 Selection of supplier . 8
6.1 General . 8
6.2 Documentation . 9
6.2.1 General. 9
6.2.2 Manufacturer audit .10
7 Biological indicators in process development .11
7.1 General .11
7.2 Overkill approach .11
7.3 Combined biological indicator and bioburden method .12
7.4 Bioburden method .13
8 Biological indicators in sterilization validation .13
8.1 General .13
8.2 Placement and handling of biological indicators .14
8.3 Sterilizer qualification .14
8.4 Performance qualification .14
8.5 Review and approval of validation .15
8.6 Requalification .15
9 Biological indicators in routine monitoring .15
9.1 General .15
9.2 Placement and handling of biological indicators .16
9.3 Process challenge device .16
10 Interpretation and acceptance criteria .17
10.1 General .17
10.2 Interpretation of results .17
11 Application of biological indicator standards .17
11.1 General assessment of biological indicator performance by the user .17
11.2 Nominal population of test organism .18
11.3 Resistance determination .19
11.3.1 General.19
11.3.2 Survivor curve method .19
11.3.3 Fraction-negative method .19
11.3.4 Survival-kill response characteristics .20
11.4 z value determination .20
11.4.1 General.20
11.4.2 Graphically plotting the z value . .20
11.4.3 Mathematically calculating the z value .21
11.4.4 Correlation coefficient, r, for the z value .22
11.5 F equivalent sterilization value determination .22
(T, z)
11.6 Establishing spore-log-reduction .22
ISO 11138-7:2019(E)
11.7 Sterility assurance level calculation .23
11.8 Test equipment .23
12 Culture conditions.24
12.1 General .24
12.2 Incubation temperature .24
12.3 Incubation period .24
12.4 Choice of growth medium .25
13 Third-party considerations .25
13.1 General .25
13.2 Minimum requirements from ISO 11138-1 for replicates and total number of
biological indicators .26
13.3 Test equipment .26
14 Personnel training .26
15 Storage and handling .27
16 Disposal of biological indicators .27
Annex A (informative) Microbiological inactivation kinetics and enumeration techniques .28
Annex B (informative) Process challenge devices .33
Annex C (informative) Formulae for D value determination by fraction-negative method .34
Annex D (informative) Examples of documentation for biological indicators prepared by
the user .50
Annex E (informative) Calculation of z value .54
Annex F (informative) D value determination by survivor curve method .57
Annex G (informative) Survival-kill response characteristics .61
Bibliography .63
iv © ISO 2019 – All rights reserved

ISO 11138-7:2019(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 198, Sterilization of health care products.
This first edition cancels and replaces ISO 14161:2009, which has been technically revised.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
ISO 11138-7:2019(E)
Introduction
This document provides guidance regarding the selection, use and interpretation of results of biological
indicators used to develop, validate and monitor sterilization processes. The procedures described
in this document are of a general nature and do not, of themselves, constitute a comprehensive
development, validation or monitoring programme with regard to the sterilization of health care
products. The intent of this document is not to stipulate the use of biological indicators in a process
but, if they are used, to provide guidance for their proper selection and use in order to avoid misleading
results.
In this document, users will find guidance on selection of the correct biological indicator for their
particular sterilization process (see the ISO 11138 series) and critical parameters as well as guidance
on its appropriate use.
The selection of an appropriate biological indicator for the particular process used is critical. There is a
wide variety of sterilization processes in common use, and biological indicator manufacturers are not
able to foresee all possible uses of their product. Manufacturers, therefore, label biological indicators
according to their intended use. It is the responsibility of the users of biological indicators to select, use,
recover and interpret the results as appropriate for the particular sterilization process used.
The performance of a biological indicator can be adversely affected by the conditions of storage and
transport prior to its use, by inappropriate/non-indicated use of the biological indicator or by the
sterilizer process parameters. In addition, the incubation procedure used after exposure to the process,
including incubation temperature and culture medium type, supplier and specific batch, can affect
measured resistance as a function of recovery and growth. For these reasons, the recommendations
of the biological indicator manufacturer for transportation, storage and use should be followed. After
exposure, the aseptic transfer (if applicable) and incubation of biological indicators as specified by the
biological indicator manufacturer is critical for obtaining correct results.
It is important to note that biological indicators are not intended to indicate that the products in the
load being sterilized are sterile. Biological indicators are utilized to test the effectiveness of a given
sterilization process and the equipment used, by assessing microbial lethality according to the concept
of sterility assurance level. Suitable training is necessary for personnel conducting these studies.
NOTE The general information provided in this document can have useful application for processes and
biological indicators not currently addressed by existing International Standards, e.g. new and developing
sterilization processes.
vi © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 11138-7:2019(E)
Sterilization of health care products — Biological
indicators —
Part 7:
Guidance for the selection, use and interpretation of results
1 Scope
This document provides guidance for the selection, use and interpretation of results from application of
biological indicators when used in the development, validation and routine monitoring of sterilization
processes.
It does not consider those processes that rely solely on physical removal of microorganisms, e.g.
filtration.
It is not applicable to combination processes using, for example, washer-disinfectors or flushing and
steaming of pipelines.
It does not specify requirements for the selection and use of biological indicators intended to monitor
vaporised hydrogen peroxide processes for isolator and room biodecontamination processes at
atmospheric pressure.
It is not applicable to liquid immersion sterilization processes.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
aseptic technique
conditions and procedures used to minimize the risk of the introduction of microbial contamination
[SOURCE: ISO 11139:2018, 3.16]
3.2
bioburden
population of viable microorganisms on or in a product and/or sterile barrier system
[SOURCE: ISO 11139:2018, 3.23]
ISO 11138-7:2019(E)
3.3
biological indicator
BI
test system containing viable microorganisms providing a specified resistance to a specified
sterilization process
[SOURCE: ISO 11139:2018, 3.29, modified — "BI" has been added to term.]
3.4
D value
D value
time or dose required under stated conditions to achieve inactivation of 90 % of a population of the test
microorganisms
[SOURCE: ISO 11139:2018, 3.75]
3.5
holding time
period during which process parameters are maintained, within their specified tolerances
[SOURCE: ISO 11139:2018, 3.133]
3.6
inoculated carrier
supporting material on or in which a specified number of viable test microorganisms has been deposited
[SOURCE: ISO 11139:2018, 3.144]
3.7
inoculation
addition of a defined amount of a characterized microbial entity into or on to an item
3.8
log reduction
LR
reduction in number of viable microorganisms
Note 1 to entry: Expressed in log units.
3.9
operational qualification
OQ
process of obtaining and documenting evidence that installed equipment operates within predetermined
limits when used in accordance with its operational procedures
[SOURCE: ISO 11139:2018, 3.220.3]
3.10
performance qualification
PQ
process of establishing by objective evidence that the process, under anticipated conditions, consistently
produces a product which meets all predetermined requirements
[SOURCE: ISO 11139:2018, 3.220.4]
3.11
process challenge device
PCD
item providing a defined resistance to a cleaning, disinfection, or sterilization process and used to
assess performance of the process
[SOURCE: ISO 11139:2018, 3.205]
2 © ISO 2019 – All rights reserved

ISO 11138-7:2019(E)
3.12
process challenge location
PCL
site chosen within a load as the position at which the least microbiological inactivation is expected to
be delivered
[SOURCE: ISO 11139:2018, 3.206]
3.13
process parameter
specified value for a process variable
Note 1 to entry: The specification for a process includes the process parameters and their tolerances.
[SOURCE: ISO 11139:2018, 3.211]
3.14
process variable
chemical or physical attribute within a cleaning, disinfection, packaging, or sterilization process,
changes in which can alter its effectiveness
EXAMPLE Time, temperature, pressure, concentration, humidity, wavelength.
[SOURCE: ISO 11139:2018, 3.213]
3.15
reference microorganism
microbial strain obtained from a recognized culture collection
[SOURCE: ISO 11139:2018, 3.228]
3.16
resistometer
test equipment designed to create specified combinations of the physical and/or chemical parameters
of a sterilization process
[SOURCE: ISO 11139:2018, 3.233]
3.17
spore log reduction
SLR
negative exponent to the base 10 describing the decrease in the number of spores
Note 1 to entry: It is expressed as a logarithm.
[SOURCE: ISO 11139:2018, 3.260]
3.18
sterile
free from viable microorganisms
[SOURCE: ISO 11139:2018, 3.271]
3.19
sterility assurance level
SAL
probability of a single viable microorganism occurring on an item after sterilization
[SOURCE: ISO 11139:2018, 3.275, modified — Note 1 to entry has been deleted.]
ISO 11138-7:2019(E)
3.20
sterilization
validated process used to render product free from viable microorganisms
Note 1 to entry: In a sterilization process, the nature of microbial inactivation is exponential and thus the survival
of a microorganism on an individual item can be expressed in terms of probability. While this probability can be
reduced to a very low number, it can never be reduced to zero.
[SOURCE: ISO 11139:2018, 3.277]
3.21
survival-kill window
extent of exposure to a sterilization process under specified conditions where there is a transition from
all biological indicators showing growth to all biological indicators showing no growth
[SOURCE: ISO 11139:2018, 3.292]
3.22
third party
person or body that is recognized as being independent of the parties involved, as concerns the issue in
question
Note 1 to entry: Parties involved are usually supplier (“first party”) and purchaser (“second party”) interests.
3.23
z value
change in temperature of a thermal sterilization or disinfection process that produces a tenfold change
in D value
Note 1 to entry: It is expressed in degree Celsius (°C).
[SOURCE: ISO 11139:2018, 3.326]
4 General
4.1 This document provides guidance on biological indicators that can apply generally for any
sterilization process, including new sterilization processes covered by ISO 14937.
4.2 The use of biological indicators is normally documented in the user’s standard operating
procedures (SOPs), procedures, or instructions.
NOTE Employing quality management systems such as ISO 13485 usually satisfies this provision.
4.3 Biological indicators should be used in combination with physical and/or chemical measurements
in demonstrating the efficacy of a sterilizing process. When a physical and/or chemical variable of
a sterilization process is outside its specified limits, the reason for the sterilizer's inability to achieve
its process parameters should be evaluated and the problem corrected. Similarly, when an indicator
failure takes place when the physical and/or chemical variables of the sterilization process are within
the specified limits, the reason for the sterilizer’s failure to inactivate the indicator should be evaluated
and the problem corrected. Systems and/or procedures should be established to evaluate any deviations
from the cycle process limits, and reasons for accepting any deviation should be fully documented.
4.4 A suitable biological indicator consists of carrier material and packaging and has a microbiological
component that is known to be suitable for handling without special containment facilities (e.g. Risk
Group 1, WHO, 2004). The growth conditions should be well documented, and the use of the indicator
should be as simple and well described as possible to avoid misinterpretation by the user.
4 © ISO 2019 – All rights reserved

ISO 11138-7:2019(E)
4.5 A biological indicator represents a microbiological challenge to a sterilization process and is used
to verify that a sterilization process has the ability to inactivate microorganisms that have a known
resistance to a referenced sterilization process. Test microorganisms employed in biological indicators
typically have resistance to sterilization which exceeds that of common bioburden microorganisms,
although some microorganisms can exhibit a resistance to sterilization in excess of that of the test
microorganisms. The appropriate biological indicator provides a challenge to the sterilization process
which exceeds that of the bioburden through a combination of population and resistance. If there
is reason to believe that the goods to be processed could be contaminated with particularly resistant
microorganisms, extended sterilization processing, based on the bioburden, could be required.
4.6 Biological indicators are not intended for use in any sterilization process other than that specified
by the biological indicator manufacturer on the product labelling. Microbial species and strains are
selected as biological indicator candidates based on their known resistance to the specific method of
sterilization. The use of an inappropriate biological indicator can give misleading results.
The user should ensure that the biological indicator has been qualified for use with the particular range
of sterilization conditions that are used. This could require information in addition to that given in
the labelling. When biological indicators are used outside reference conditions, the user can require
information on the reaction expected from the indicator, e.g. the effect of sub-optimal moisture
conditions on the biological indicators used in an ethylene oxide process. Users who employ biological
indicators outside the manufacturer’s labelled recommendations should thoroughly characterize the
resistance of the biological indicators to the particular sterilization process. The relationship of the
response of the biological indicator to process parameters should be clearly demonstrated.
4.7 The user who is responsible for the sterilization of product should ensure that the type of biological
indicator employed to validate and/or routinely monitor a given sterilization process is appropriate for
that use.
4.8 The manufacturer’s recommendations for the transportation, storage and use of the biological
indicators should always be followed. Failure to do so can compromise the performance characteristics
of the biological indicator. If the user removes the inoculated carrier from the biological indicator’s
primary packaging, or adds additional packaging over the primary packaging, changes in the resistance
characteristics can occur. Guidance should be sought from the manufacturer on the extent of this change,
or the user can evaluate changes in the resistance characteristics. The user should document that the
performance characteristics of the inoculated carrier are appropriate for their use.
4.9 Biological indicators should not be used beyond the expiration date stated by the manufacturer.
4.10 Users who employ biological indicators for sterilization process development, validation and/or
routine monitoring of sterilization should be properly trained in their use.
4.11 The time between completion of sterilization process and incubation should be within the
manufacturer’s stated time or should be justified as described in 8.2.3.
4.12 Transfer of microorganisms exposed to the sterilization process to the appropriate recovery
medium should be done using aseptic technique.
4.13 Self-contained biological indicators are specifically designed to eliminate the need for aseptic
handling because all of the components required to effect post process incubation are enclosed within
the primary packaging which need not be opened (see 5.4).
4.14 The ISO 11138 series gives requirements for the information that the manufacturer shall provide
for biological indicators. The information might be provided on the label, as a packet insert or as a general
specification accompanying the biological indicators. The ISO 11138 series also includes minimum
requirements for resistance characteristics. Testing conditions and methods are given as reference
methods.
ISO 11138-7:2019(E)
4.15 Users of biological indicators come from a wide variety of industries, private enterprises and health
care facilities. Users are not generally required to perform resistance assays on biological indicators
but can have differing requirements for their quality assurance systems, which may include audits by
regulators or Notified Bodies (see 6.2.2). If a user wishes to carry out a population and/or resistance
determination it is essential that they use the method specified by the manufacturer.
4.16 The verification of resistance characteristics by the user is an alternative to and/or complementary
to an audit, when necessary.
5 Characteristics of biological indicators
5.1 General
5.1.1 Biological indicators provide means to assess directly the microbial lethality of a sterilization
process (see ISO 13485 and Reference [16]). When used in conjunction with physical and/or chemical
process monitors, biological indicators can provide an indication of the effectiveness of a given
sterilization process.
Biological indicators, in their simplest form, consist of an inoculated carrier in primary packaging. The
inoculated carrier can take a variety of forms, including paper strips, threads, metal coupons or other
carriers suitable for inoculation. The primary packaging is chosen to permit the sterilizing agent to
penetrate to the inoculated carrier while maintaining a sterile barrier after processing.
5.1.2 A sterilization process should be considered as satisfactory only when the desired physical
and/or chemical parameters and microbiological results, as determined by an appropriate sterilization
process development, validation and monitoring programme have been realized. Failure to achieve
the desired physical and/or chemical parameters and/or microbiological challenge forms the basis for
declaring the sterilization process as nonconforming (see ISO 13485 and ISO 9001).
5.1.3 Biological indicators consist of a defined population of test organisms presented in such a
manner as to allow their recovery following sterilization processing. For example, test organisms
employed for ethylene oxide sterilization processes can be spores of a suitable strain of Bacillus subtilis
or Bacillus atrophaeus, as noted in ISO 11138-2. For steam sterilization or moist heat sterilization, the
test organisms employed can be spores of a suitable strain of Geobacillus stearothermophilus, as noted in
ISO 11138-3. Test organisms other than bacterial spores can be used if they have been shown to provide
appropriate resistance to the sterilization process.
5.1.4 The basis of all formulae used to determine biological indicator resistance characteristics such as
D values is that the inactivation reaction follows first-order log-linear kinetics, with the requirement that
the value for the coefficient of determination, r , for the linearity of the survivor curve be not less than
0,8 (see Annexes E and F). The strain of the test organism, the production method, the suspension fluid,
the carrier and packaging materials and the testing conditions all affect the resistance characteristics of
the biological indicators (see ISO 11138-1).
5.1.5 The design and construction of a biological indicator can result in unique resistance
characteristics and can vary depending on whether the biological indicator is intended for use in the
development and validation of a sterilization process or for use in routine monitoring. If the design of the
biological indicator for use in routine monitoring differs from that employed to validate the sterilization
processes, the challenge to the process during validation should be correlated with the challenge to the
process during routine monitoring.
5.1.6 Depending upon placement within the load and the specific sterilization process conditions at
those discrete locations, biological indicators from the same batch can show different survival capabilities
(see 7.2.3). Users of biological indicators should note that 10 indicators spread throughout the load are
6 © ISO 2019 – All rights reserved

ISO 11138-7:2019(E)
not considered replicates due to the differences in lethality that may exist throughout the chamber and
load (see Note to 11.3.1).
5.2 Test organism suspension for direct inoculation of products
5.2.1 Direct inoculation of test organisms on or in product can be necessary in process development
and other studies when the use of a biological indicator is not feasible. Direct inoculation can be
appropriate for assessing factors such as product sterilisability, identification of the most difficult to
sterilize locations within the device, and localized microbiological effects, e.g. moist heat versus dry heat
environments.
The rationale for the selection of the “most difficult-to-sterilize” site(s) on a product or within a
sterilization load should be documented based on experimental data or derived from prior knowledge
of the particular sterilization methodology. In practice, the “most difficult-to-sterilize” site represents
those locations that are most likely to provide high resistance to the sterilization process. One should
refer to specific sterilization standards (e.g. ISO 17665-1 and ISO 11135) for guidance in determining
and selecting difficult-to-sterilize locations.
5.2.2 To assess the efficacy of sterilization at a particular site or location on the product, the desired
species and population of test organisms can be inoculated at those sites. The use of suspensions of
test organisms to prepare inoculated carriers or inoculated products requires caution. This is because
the materials on to which test organisms are inoculated can alter the test organisms’ resistance
characteristics. The resistance can be higher or lower due to deposition as a monolayer or multilayer
(clumping), coating effects, and/or bacteriostatic or bactericidal effects of the material.
5.2.3 The methods used to recover test organisms should be validated to ensure an adequate level
of recovery from the product (see ISO 11737-1). Test organism recovery should be expressed in terms
of percent recovery of the population of the original inoculum. A change in survival characteristics of
test organisms due to inoculation can affect the observed percent recovery of the orig
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