oSIST prEN ISO 11737-1:2026

SLOVENSKI STANDARD
01-maj-2026
Sterilizacija izdelkov za zdravstveno nego - Mikrobiološke metode - 1. del:
Določevanje populacije mikroorganizmov na izdelkih (ISO/DIS 11737-1:2026)
Sterilization of health care products - Microbiological methods - Part 1: Determination of
a population of microorganisms on products (ISO/DIS 11737-1:2026)
Sterilisation von Produkten für die Gesundheitsfürsorge - Mikrobiologische Verfahren -
Teil 1: Bestimmung der Population von Mikroorganismen auf Produkten (ISO/DIS 11737-
1:2026)
Stérilisation des produits de santé - Méthodes microbiologiques - Partie 1: Détermination
d'une population de microorganismes sur des produits (ISO/DIS 11737-1:2026)
Ta slovenski standard je istoveten z: prEN ISO 11737-1
ICS:
07.100.10 Medicinska mikrobiologija Medical microbiology
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.

DRAFT
International
Standard
ISO/DIS 11737-1
ISO/TC 198
Sterilization of health care
Secretariat: ANSI
products — Microbiological
Voting begins on:
methods —
2026-03-06
Part 1:
Voting terminates on:
2026-05-29
Determination of a population of
microorganisms on products
Stérilisation des produits de santé — Méthodes
microbiologiques —
Partie 1: Détermination d'une population de microorganismes
sur des produits
ICS: 07.100.10; 11.080.01
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FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
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INTERNATIONAL STANDARD UNTIL
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This document is circulated as received from the committee secretariat.
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Reference number
ISO/DIS 11737-1:2026(en)
DRAFT
ISO/DIS 11737-1:2026(en)
International
Standard
ISO/DIS 11737-1
ISO/TC 198
Sterilization of health care
Secretariat: ANSI
products — Microbiological
Voting begins on:
methods —
Part 1:
Voting terminates on:
Determination of a population of
microorganisms on products
Stérilisation des produits de santé — Méthodes
microbiologiques —
Partie 1: Détermination d'une population de microorganismes
sur des produits
ICS: 07.100.10; 11.080.01
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
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Published in Switzerland Reference number
ISO/DIS 11737-1:2026(en)
ii
ISO/DIS 11737-1:2026(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 5
5 Selection of products . 5
5.1 General .5
5.2 Sample item portion (SIP) .5
6 Methods of determination and microbial characterization of bioburden . 6
6.1 Determination of bioburden .6
6.1.1 Selection of an appropriate method .6
6.1.2 Neutralization of inhibitory substances.6
6.1.3 Recovery of microorganisms .6
6.1.4 Detecting viable microorganisms .7
6.1.5 Enumeration of microorganisms .7
6.2 Microbial characterization of bioburden .7
7 Validation of the method for determining bioburden . 7
7.1 General .7
7.2 Validation .8
8 Routine determination of bioburden and interpretation of data . 8
8.1 General .8
8.2 Limits of detection and plate counting .8
8.3 Microbial characterization .8
8.4 Use of bioburden data for determination of the extent of treatment .8
8.5 Bioburden spikes .8
8.6 Bioburden levels .9
8.7 Data analysis .9
8.8 Statistical methods .9
9 Assessment of change for bioburden determination . 9
9.1 Changes to the product or manufacturing process .9
9.2 Changes to the method for determining bioburden .9
9.3 Requalification of the method for determining bioburden .9
9.4 Review of appropriateness of bioburden levels .9
Annex A (informative) Guidance on the determination of a population of microorganisms on
products . 10
Annex B (informative) Guidance on methods to determine bioburden .25
Annex C (informative) Establishment of bioburden recovery efficiency .35
Annex D (informative) Guidance on bioburden method suitability testing for health care
products .43
Annex E (informative) Guidelines for counting plates and recording results .46
Annex F (informative) Bioburden excursions .50
Annex G (informative) Typical assignment of responsibilities .53
Annex ZA (informative) Relationship between this European standard and the General Safety
and Performance Requirements of Regulation (EU) 2017/745 aimed to be covered .55
Annex ZB (informative) Relationship between this European standard and the General Safety
and Performance Requirements of Regulation (EU) 2017/746 aimed to be covered .59

iii
ISO/DIS 11737-1:2026(en)
Bibliography .63

iv
ISO/DIS 11737-1:2026(en)
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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 in
collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 204,
Sterilization of medical devices, in accordance with the Agreement on technical cooperation between ISO and
CEN (Vienna Agreement).
This fourth edition cancels and replaces the third edition (ISO 11737-1:2018), which has been technically
revised.
The main changes are as follows:
— incorporation of the amendment content.
A list of all parts in the ISO 11737 series can be found on the ISO website.
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.

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ISO/DIS 11737-1:2026(en)
Introduction
A sterile health care product is one that is free of viable microorganisms. International Standards that specify
requirements for the validation and routine control of sterilization processes require, when it is necessary
to supply a sterile health care product, that adventitious microbiological contamination of a health care
product prior to sterilization be minimized. Such products are non-sterile. The purpose of sterilization is
to inactivate the microbiological contaminants and thereby transform the non-sterile products into sterile
ones.
The kinetics of inactivation of a population of microorganisms by physical or chemical agents used to
sterilize health care products can generally best be described by an exponential relationship between the
numbers of microorganisms surviving and the extent of treatment with the sterilizing agent. Inevitably,
this means there is always a finite probability that a microorganism can survive regardless of the extent
of treatment applied. For a given treatment, the probability of survival is determined by the number and
resistance of microorganisms and by the environment in which the microorganisms exist during treatment.
It follows that the sterility of any one product in a population subjected to sterilization processing cannot be
guaranteed and the sterility of a processed population is defined in terms of the probability of there being a
viable microorganism present on a product item.
Generic requirements of the quality management system for design and development, production,
installation and servicing are given in ISO 9001 and particular requirements for quality management
systems for medical device production are given in ISO 13485. The standards for quality management
systems recognize that, for certain processes used in manufacturing, the effectiveness of the process cannot
be fully verified by subsequent inspection and testing of the product. Sterilization is an example of such a
process. For this reason, sterilization processes are validated for use, the performance of the sterilization
process is monitored routinely and the equipment is maintained.
International Standards specifying procedures for the validation and routine control of the processes used
for the sterilization of health care products have been prepared (see, for example, ISO 14937, ISO 11135,
the ISO 11137 series, ISO 13004, ISO 17665, ISO 14160, ISO 20857, ISO 22441 and ISO 25424). However,
it is important to be aware that exposure to a properly validated and accurately controlled sterilization
process is not the only factor associated with the provision of assurance that the product is sterile and, in
this respect, suitable for its intended use. Furthermore, for the effective validation and routine control of
a sterilization process, it is important to be aware of the microbiological challenge that is presented in the
process, in terms of number, characteristics and properties of microorganisms.
The term “bioburden” is used to describe the population of viable microorganisms present on or in a product
and a sterile barrier system. A knowledge of bioburden can be used in a number of situations as part of the
following:
— validation and requalification of sterilization processes;
— routine monitoring for control of manufacturing processes;
— monitoring of raw materials, components or packaging;
— assessment of the efficiency of cleaning processes;
— evaluation of change in a manufacturing process or location;
— an overall environmental monitoring programme.
Bioburden is the sum of the microbial contributions from a number of sources, including people, raw
materials, manufacturing of components, assembly processes, manufacturing environment, assembly/
manufacturing aids (e.g. compressed gases, water, lubricants), cleaning processes and packaging of finished
products. To control bioburden, attention should be given to the microbiological status of these sources.
It is not possible to enumerate bioburden precisely and, in practice, a determination of bioburden is
relative to the defined method used. Definition of a single method for use in determining bioburden in all
situations is not practicable because of the wide variety of designs and materials of construction of health
care products. Nor is it possible to define a single technique to be used in all situations for the extraction

vi
ISO/DIS 11737-1:2026(en)
of microorganisms in preparation for enumeration. Furthermore, the selection of culture conditions for
enumeration of microorganisms will be influenced by the types of microorganism likely to be present on or
in health care products.
This document specifies the requirements to be met for the determination of bioburden. In addition, it gives
guidance in the annexes to provide explanations and methods that are deemed suitable to conform with the
requirements. Methods other than those given in the guidance may be used, if they are effective in achieving
conformity with the requirements of this document.

vii
DRAFT International Standard ISO/DIS 11737-1:2026(en)
Sterilization of health care products — Microbiological
methods —
Part 1:
Determination of a population of microorganisms on
products
1 Scope
This document specifies requirements and provides guidance on the enumeration and microbial
characterization of the population of viable microorganisms on or in a health care product, component, raw
material or package.
NOTE 1 The nature and extent of microbial characterization is dependent on the intended use of bioburden data.
This document does not apply to the enumeration or characterization of viral, prion or protozoan
contaminants. This includes the extraction and detection of the causative agents of transmissible spongiform
encephalopathies, such as scrapie, bovine spongiform encephalopathy and Creutzfeldt-Jakob disease.
NOTE 2 Guidance on inactivating viruses and prions can be found in ISO 22442-3, ICH Q5A(R1) and ISO 13022.
NOTE 3 ISO/TS 22456 provides specific guidance for bioburden testing for biologics and tissue-based products
where this testing is conducted in relation to product sterilization.
This document does not apply to the microbiological monitoring of the environment in which health care
products are manufactured.
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 terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
action level
value from monitoring that necessitates immediate intervention
[SOURCE: ISO 11139:2018, 3.5]
3.2
alert level
value from monitoring providing early warning of deviation from specified conditions
[SOURCE: ISO 11139:2018, 3.11]

ISO/DIS 11737-1:2026(en)
3.3
batch
defined quantity of a product (3.18) intended or purported to be uniform in character and quality produced
during a specified cycle of manufacture
[SOURCE: ISO 11139:2018, 3.21]
3.4
bioburden
population of viable microorganisms on or in a product (3.18) and/or sterile barrier system (3.24)
[SOURCE: ISO 11139:2018, 3.23]
3.5
bioburden correction factor
numerical value applied to a viable count to compensate for incomplete removal of microorganisms from a
product (3.18) and/or failure to culture microorganisms
[SOURCE: ISO 11139:2018, 3.24]
3.6
bioburden estimate
value established (3.11) by applying a bioburden correction factor (3.5) to a bioburden (3.4) count
Note 1 to entry: The recovery efficiency can also be used to determine the bioburden estimate.
[SOURCE: ISO 11139:2018, 3.25, modified — “bioburden” has been added to the referenced term “correction
factor.”]
3.7
bioburden method suitability
assessment of the test method to demonstrate its ability to allow microbial growth
[SOURCE: ISO 11139:2018, 3.168, modified — “bioburden” has been added to the term.]
3.8
bioburden spike
individual bioburden (3.4) value that is significantly greater than other bioburden values in a set
[SOURCE: ISO 11139:2018, 3.26]
3.9
corrective action
action to eliminate the cause of a nonconformity and to prevent recurrence
Note 1 to entry: There can be more than one cause for a nonconformity.
Note 2 to entry: Corrective action is taken to prevent recurrence whereas preventive action (3.17) is taken to prevent
occurrence.
[SOURCE: ISO 9000:2015, 3.12.2, modified — Note 3 to entry has been deleted.]
3.10
culture condition
combination of growth media and manner of incubation used to promote germination, growth, and/or
multiplication of microorganisms
Note 1 to entry: The manner of incubation can include the temperature, time, and any other conditions specified for
incubation.
[SOURCE: ISO 11139:2018, 3.70]

ISO/DIS 11737-1:2026(en)
3.11
establish
determine by theoretical evaluation and confirm by experimentation
[SOURCE: ISO 11139:2018, 3.107]
3.12
excursion
data exceeding an established level
Note 1 to entry: Bioburden results are typically evaluated as averages of a number of individual values.
[SOURCE: AAMI TIR106:2024, 3.2]
3.13
facultative microorganism
microorganism capable of both aerobic and anaerobic metabolism
[SOURCE: ISO 11139:2018, 3.114]
3.14
health care product
medical device, including in vitro diagnostic medical device, or medicinal product (3.18), including
biopharmaceutical
[SOURCE: ISO 11139:2018, 3.132]
3.15
microbial characterization
process by which microorganisms are grouped into categories
Note 1 to entry: Categories can be broadly based, for example, on the use of selective media, colony or cellular
morphology, staining properties, or other characteristics.
[SOURCE: ISO 11139:2018, 3.170]
3.16
obligate anaerobe
organism that only lives and grows in the absence of molecular oxygen
[SOURCE: ISO 11139:2018, 3.186]
3.17
preventive action
action to eliminate the cause of a potential nonconformity or other potential undesirable situation
Note 1 to entry: There can be more than one cause for a potential nonconformity.
Note 2 to entry: Preventive action is taken to prevent occurrence whereas corrective action (3.10) is taken to prevent
recurrence.
[SOURCE: ISO 9000:2015, 3.12.1]
3.18
product
tangible result of a process
EXAMPLE Raw material(s), intermediate(s), sub-assembly(ies), health care product(s) (3.15).
[SOURCE: ISO 11139:2018, 3.217]

ISO/DIS 11737-1:2026(en)
3.19
product family
group or subgroup of product (3.18) characterized by similar attributes determined to be equivalent for
evaluation and processing purposes
[SOURCE: ISO 11139:2018, 3.218]
3.20
recovery efficiency
measure of the ability of a specified technique to remove, collect, and/or culture microorganisms
from a product (3.18)
[SOURCE: ISO 11139:2018, 3.225]
3.21
requalification
repetition of part or all of validation (3.25) for the purpose of confirming the continued acceptability of a
specified process
[SOURCE: ISO 11139:2018, 3.220.5]
3.22
sample item portion
SIP
specified part of a health care product (3.14) that is tested
[SOURCE: ISO 11139:2018, 3.240, modified — acronym SIP has been added.]
3.23
sterile
free from viable microorganisms
[SOURCE: ISO 11139:2018, 3.271]
3.24
sterile barrier system
SBS
minimum package that minimizes the risk of ingress of microorganisms and allows aseptic presentation of
the sterile (3.23) contents at the point of use
[SOURCE: ISO 11139:2018, 3.272]
3.25
terminally sterilized
condition of a product (3.18) that has been exposed to a sterilization process in its sterilized barrier system
[SOURCE: ISO 11139:2018, 3.296]
3.26
validation
confirmation process, through the provision of objective evidence, that the requirements for a specific
intended use or application have been fulfilled
Note 1 to entry: The objective evidence needed for a validation is the result of a test or other form of determination such
as performing alternative calculations or reviewing documents.
Note 2 to entry: The word “validated” is used to designate the corresponding status.
Note 3 to entry: The use conditions for validation can be real or simulated.
[SOURCE: ISO 9000:2015, 3.8.13, modified — “process” has been added to the definition.]

ISO/DIS 11737-1:2026(en)
4 General
4.1 The development, validation and routine control of bioburden are critical elements in the realization of
some types of health care products. To ensure the consistent implementation of the requirements specified
in this document, the necessary processes shall be established, implemented and maintained. Processes of
particular importance in relation to the development, validation and routine bioburden control of a process
include but are not limited to:
— control of documentation, including records;
— assignment of management responsibility;
— provision of adequate resources, including competent human resources and infrastructure;
— control of product provided by external parties;
— identification and traceability of product throughout the process; and
— control of non-conforming product.
NOTE 1 ISO 13485 covers all stages of the lifecycle of medical devices in the context of quality management systems
for regulatory purposes. National or regional regulatory requirements for the provision of health care product can
require the implementation of a full quality management system and the assessment of that system by a recognized
conformity assessment body.
NOTE 2 See Annex G for information on typical assignment of responsibilities.
4.2 A process shall be specified for the calibration of equipment, as applicable, used in meeting the
requirements of this document (e.g. instrumentation for test purposes).
5 Selection of products
5.1 General
5.1.1 The procedures for the selection and handling of products for the determination of bioburden shall
ensure that the selected product is representative of routine production, including primary packaging
materials and processes, but prior to the terminal sterilization process, if applicable. Terminally sterilized
product should not be used for bioburden testing.
5.1.2 If product(s) are grouped in a product family for the purpose of the determination of bioburden,
the rationale for inclusion of a product within a product family shall be documented. The rationale shall
include criteria to ensure that bioburden determined for a product selected from the product family is
representative for the whole product family.
5.1.3 Consideration shall be given to the timing of the determination of bioburden relative to manufacturing
because bioburden can change with the passage of time.
5.2 Sample item portion (SIP)
5.2.1 The determination of bioburden may be performed on:
a) the entire product (SIP = 1,0);
b) a portion of the product, e.g. half of the product for an SIP of 0,5, or;
c) the sterile fluid path for which sterility is claimed (SIP = 1,0).

ISO/DIS 11737-1:2026(en)
5.2.2 The selection of sample portions for an SIP <1,0 shall be based on the following criteria and should
be reviewed periodically:
a) if the bioburden distribution is known and is evenly distributed, the SIP may be selected from any
portion of the item;
b) if the bioburden distribution is not known or is known and is unevenly distributed the SIP shall include:
1. portions of the product selected that proportionally represent each of the materials (e.g. 30 %)
composing the product; or
2. alternatively, only where the bioburden distribution is known and is unevenly distributed, the SIP
can be selected from the portion of the product that contains the most severe microbial challenge
(numbers and types) to the sterilization process.
5.2.3 The SIP can be calculated on the basis of measurable physical characteristics, such as length, mass,
volume or surface area (see Table A.1 for examples).
NOTE Some standards specify requirements for validation and routine control of the sterilization process
stipulate criteria for the adequacy of the SIP, e.g. the ISO 11137 series.
6 Methods of determination and microbial characterization of bioburden
6.1 Determination of bioburden
6.1.1 Selection of an appropriate method
The method shall be appropriate to the purpose for which the data are to be used. The method(s) shall
comprise techniques for the following:
a) neutralization of inhibitory substances, if needed;
b) extraction of microorganisms, if appropriate;
c) a means of detecting viable microorganisms e.g. culture or non-culture based;
d) enumeration of microorganisms.
6.1.2 Neutralization of inhibitory substances
If the physical or chemical nature of the product or SIP is such that substances can be released that adversely
affect the detection of the product bioburden, then a system shall be used to neutralize, remove or, if this is
not possible, minimize the effect of any such released substance. The effectiveness of such a system shall be
demonstrated.
NOTE Annexes B and D describe techniques that can be used to assess the release of microbicidal or microbiostatic
substances.
6.1.3 Recovery of microorganisms
6.1.3.1 For a product that cannot be directly cultured and where the extraction of microorganisms is part
of the method, the need for recovery studies (or bioburden recovery efficiency) shall be considered using
risk-based approach and the outcomes of this consideration documented. Consideration shall, at least, be
given to the following:
a) ability of the technique to remove microorganisms;
b) possible type(s) of microorganism(s) and their location(s) on the product;
c) effect(s) of the extraction technique on the viability of microorganisms;

ISO/DIS 11737-1:2026(en)
d) the physical or chemical nature of the product under test.
6.1.3.2 For a product where the extraction of microorganisms is not part of the method (e.g. direct culture
of a product), consideration shall, at least, be given to the following:
a) possible type(s) of microorganism(s) and their location(s) on or in the product;
b) the physical or chemical nature of the product under test.
6.1.4 Detecting viable microorganisms
Culture conditions shall be selected based on consideration of the types of microorganisms likely to be
present and the physical or chemical nature of the product to be tested.
6.1.5 Enumeration of microorganisms
The technique for enumeration shall be selected after consideration of the types of microorganisms likely to
be present.
6.2 Microbial characterization of bioburden
6.2.1 Appropriate techniques for microbial characterization of bioburden shall be selected.
NOTE Microbial characterization supports detecting a change to the product bioburden that can affect some
aspects of the use of bioburden data (e.g. establishing or maintaining a sterilization process). Furthermore, knowledge
of the types of microorganisms can be helpful for identifying sources of contamination.
6.2.2 Bioburden shall be characterized using one or more of the following technique(s):
a) colony morphology;
b) cell morphology;
c) differential staining;
d) culture using selective or differential conditions;
e) biochemical properties;
f) genotypic analysis, e.g. pattern or fingerprint-based techniques or sequence-based techniques;
g) proteomic methods, e.g. mass spectrometry;
h) other technologies.
Additional guidance on microbial characterization of bioburden for radiation-sterilized product is provided
in ISO 11137-1.
7 Validation of the method for determining bioburden
7.1 General
The method(s) for determining bioburden shall be validated and documented.
NOTE See A.7.1 for information on validation and the use of classic microbiological methods.

ISO/DIS 11737-1:2026(en)
7.2 Validation
Validation shall consist of the following:
a) if applicable, assessment of test method suitability to demonstrate lack of inhibition of growth in the
test (see 6.1.2);
NOTE 1 Several techniques can support the absence of inhibition of growth such as data from bioburden
recovery efficiency testing, if an inoculated product was used, or information from method suitability testing
from the test of sterility (bacteriostasis/fungistasis). See B.8 and Annex D for guidance on necessity of inhibition
tests for information on test method suitability.
b) assessment of the technique for the extraction of microorganisms from a product or SIP if the extraction
is part of the method (i.e. bioburden recovery efficiency), if appropriate for the purpose for which the
data are being generated;
NOTE 2 Annex C provides information on the determination of bioburden recovery efficiency.
c) assessment of the technique for the enumeration of microorganisms, including culture conditions and
microbiological counting techniques;
d) assessment of the suitability of the technique(s) of microbial characterization to the extent it is used.
8 Routine determination of bioburden and interpretation of data
8.1 General
Routine determination of bioburden shall be performed by employing documented sampling plan(s) that
specify sample size, sampling frequency, sample preparation (e.g. SIP), where applicable, and the test method
to be performed. Bioburden data shall be analysed over time to determine and monitor changes in numbers
and types (i.e. microbial characterization) of microorganisms.
8.2 Limits of detection and plate counting
The determination of bioburden shall be performed using the method(s) specified for a product or a product
family (see 5.1.2). The method selected shall consider factors that will affect the results, such as the limits of
detection and plate counting.
8.3 Microbial characterization
Microbial characterization shall be performed. The extent of characterization is dependent on the intended
use of the data.).
8.4 Use of bioburden data for determination of the extent of treatment
If bioburden data are to be used to establish or maintain the extent of treatment with a sterilization process
(i.e. bioburden-based method), any requirements applicable to the use of bioburden data, specified in the
appropriate standard for the development, validation and routine control of the sterilization process, shall
be met.
8.5 Bioburden spikes
If bioburden data demonstrate a test result that is unexpectedly greater than other values within the data set
(bioburden spike), these data shall be evaluated to determine possible causes and for impact as appropriate
depending on the purpose for the data.

ISO/DIS 11737-1:2026(en)
8.6 Bioburden levels
Acceptable levels for bioburden on or in a product or group of products shall be specified (e.g. alert and
action levels). Acceptable levels shall be reviewed periodically and revised as necessary per a documented
procedure. The results of the review shall be documented.
If alert or action levels are exceeded, a predetermined response shall be carried out in accordance with a
documented procedure.
8.7 Data analysis
Data derived from the determination of bioburden obtained over a period of time, including microbial
characterization, shall be used to identify trends.
8.8 Statistical methods
If applied, statistical methods can be used to define sample size, sampling frequency or acceptable levels.
9 Assessment of change for bioburden determination
9.1 Changes to the product or manufacturing process
Changes to the product or manufacturing process shall be reviewed to determine whether they are likely
to alter the ability of the test method to measure bioburden with consideration to the purpose for which
bioburden data are to be used. The results of the review shall be documented. If there is potential for
alteration of bioburden, specific determinations of bioburden shall be performed to evaluate the extent and
nature of any effect of the change.
NOTE The assessment of the change can indicate that the previous method suitability and bioburden recovery
efficiency are still applicable.
9.2 Changes to the method for determining bioburden
Any change to a routine method of bioburden determination shall be assessed. This assessment shall include
evaluation of the effect of the change on the outcome of determination. The results of the assessment shall
be documented.
NOTE The assessment of the change can indicate that the previous method suitability and bioburden recovery
efficiency are still applicable.
9.3 Requalification of the method for determining bioburden
The original validation data (see 7.2) and any subsequent requalification data shall be reviewed at specified
intervals in accordance with a documented procedure. The outcome of the review and any requalification
undertaken shall be documented.
9.4 Review of appropriateness of bioburden levels
When such changes are made that can impact bioburden alert and action levels, the continued appropriateness
of bioburden levels shall be assessed and revised if appropriate.

ISO/DIS 11737-1:2026(en)
Annex A
(informative)
Guidance on the determination of a population of microorganisms on
products
NOTE For ease of reference, the numbering in this annex corresponds to that used in the main body of this
document.
A.1 Related to the Scope
This annex gives guidance on the implementation of the requirements specified in this document. The
guidance given is not intended to be exhaustive, but to highlight important aspects to which attention should
be given.
Methods other than those given in this annex may be used, but these alternative methods should be
demonstrated as being effective in achieving conformity with the requirements of this document.
This annex is not intended as a checklist for assessing conformity with the requirements of this document.
Though microbiological characterization is a tool to understand product bioburden, its information is
relative to its intended use, and this document does not specify the impact of characterized microorganisms
on the effectiveness of the sterilization process.
A.2 Related to the Normative references
No guidance offered.
A.3 Related to the Terms and definitions
No guidance offered.
A.4 General
A.4.1 No guidance offered.
A.4.2 No guidance offered.
A.5 Selection of products
A.5.1 General
A.5.1.1 When selecting and handling product samples the introduction of microbiological contamination
and significant alterations to the numbers and types of microorganisms in the sample should be avoided.
Sampling techniques should be consistent and should allow for event-based and time-based comparisons of
bioburden.
In choosing product samples for the determination of bioburden, there are several possibilities including
a) select samples from routine product (at random or at a specified frequency);
...