Water quality - Requirements for the performance testing of membrane filters used for direct enumeration of microorganisms by culture methods (ISO/FDIS 7704:2022)

This International Standard specifies requirements for the evaluation of membrane filters intended for the concentration for direct enumeration of specific microorganisms and mixed populations. These requirements are applicable to all membrane filters intended for the microbiological analysis of all kinds of water and other liquid samples.
These requirements are intended for the test to demonstrate the suitability of the whole system - membrane filter together with culture medium including the filtration step - required for specific tests described in International Standards.
The membrane filters required for use are described in each specific standard. This International Standard applies to producers and users such as:
— commercial bodies producing and/or distributing membrane filters;
— non-commercial bodies supplying membrane filters to third parties;
— microbiological laboratories using membrane filters for their own testing or providing these to other users.

Wasserbeschaffenheit - Anforderungen für die Bewertung von Membranfiltern zur direkten Zählung mittels mikrobiologischer Kulturverfahren (ISO/FDIS 7704:2022)

Dieses Dokument legt die Anforderungen an die Leistungsprüfung von Membranfiltern fest, die für die Rückhaltung und die anschließende direkte Zählung von Mikroorganismen durch Verfahren zur Kultivierung verwendet werden.
Dieses Dokument gilt für Membranfilter, die für die Rückhaltung und anschließende direkte Zählung bestimmter Mikroorganismen auf festen Medien oder auf anderen Vorrichtungen, die Medien enthalten, wie absorbierendes Trägermaterial, verwendet werden [19].
Dieses Dokument gilt nicht für Membranfilter, die zur Aufkonzentrierung und Elution oder für qualitative Verfahren verwendet werden.
Die Prüfungen gelten für Membranfilter, die für die mikrobiologische Analyse verschiedener Arten von Wasser bestimmt sind, wie:
   Trinkwasser, in Flaschen abgefülltes Wasser und andere Arten von Wasser mit voraussichtlich geringer Anzahl von Mikroorganismen;
   Wasser mit einer erwarteten höheren Anzahl von Mikroorganismen, z. B. Oberflächenwasser und Prozesswasser.
Die Prüfungen sollen die Eignung des gesamten Systems (Membranfilter zusammen mit dem Nährmedium einschließlich der Filtrationsstufe) nachweisen, die für die in den Literaturhinweisen [3] [6] [8] [10] [12] und [13] beschriebenen spezifischen Prüfungen erforderlich ist.
Dieses Dokument gilt für:
   Hersteller, die Membranfilter produzieren;
   Laboratorien für Mikrobiologie, die Membranfilter für ihre eigenen Prüfungen verwenden oder diese an andere Endanwender liefern.

Qualité de l'eau - Exigences relatives aux essais de performance des membranes filtrantes utilisées pour le dénombrement direct des micro-organismes par des méthodes de culture (ISO/FDIS 7704:2022)

Le présent document spécifie les exigences pour les essais de performance des membranes filtrantes utilisées pour la rétention suivie d'un dénombrement direct des micro-organismes par des méthodes de culture.
Le présent document s'applique aux membranes filtrantes qui sont utilisées pour la rétention suivie d'un dénombrement direct de micro-organismes spécifiques sur des milieux solides ou sur d'autres dispositifs contenant des milieux, comme des pads en papier absorbants [19].
Le présent document ne s'applique pas aux membranes filtrantes utilisées pour la concentration et l'élution ou pour des méthodes qualitatives.
Les essais s'appliquent aux membranes filtrantes destinées à l'analyse microbiologique de différents types d'eau, tels que:
—    l'eau potable, l'eau embouteillée et d'autres types d'eau dans laquelle un faible nombre de micro-organismes est attendu;
—    l'eau dans laquelle un plus grand nombre de micro-organismes est attendu, par exemple l'eau de surface et l'eau de process.
Ces essais sont destinés à démontrer l'adéquation de l'ensemble du système (membrane filtrante et milieu de culture, y compris l'étape de filtration) requis pour les essais spécifiques décrits dans les Références [3], [6], [8], [10], [12] et [13].
Le présent document s'applique:
—    aux fabricants produisant des membranes filtrantes;
—    aux laboratoires de microbiologie utilisant des membranes filtrantes pour leurs propres essais ou les fournissant à d'autres utilisateurs finaux.

[Not translated]

General Information

Status
Not Published
Public Enquiry End Date
01-Dec-2020
Technical Committee
Current Stage
5020 - Formal vote (FV) (Adopted Project)
Start Date
09-Sep-2022
Due Date
28-Oct-2022
Completion Date
17-Oct-2022

Buy Standard

Draft
oSIST prEN ISO 7704:2021
English language
40 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN ISO 7704:2021
01-november-2021
[Not translated]

Water quality - Requirements for the performance testing of membrane filters used for

direct enumeration of microorganisms by culture methods (ISO/DIS 7704:2021)
Wasserbeschaffenheit - Anforderungen für die Bewertung von Membranfiltern zur
direkten Zählung mittels mikrobiologischer Kulturverfahren (ISO/DIS 7704:2021)

Qualité de l'eau - Évaluation des membranes filtrantes utilisées pour des analyses

microbiologiques (ISO/DIS 7704:2021)
Ta slovenski standard je istoveten z: prEN ISO 7704
ICS:
07.100.20 Mikrobiologija vode Microbiology of water
oSIST prEN ISO 7704:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN ISO 7704:2021
---------------------- Page: 2 ----------------------
oSIST prEN ISO 7704:2021
DRAFT INTERNATIONAL STANDARD
ISO/DIS 7704
ISO/TC 147/SC 4 Secretariat: DIN
Voting begins on: Voting terminates on:
2021-10-07 2021-12-30
Water quality — Requirements for the performance
testing of membrane filters used for direct enumeration of
microorganisms by culture methods
ICS: 07.100.20
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 7704:2021(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO 2021
---------------------- Page: 3 ----------------------
oSIST prEN ISO 7704:2021
ISO/DIS 7704:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 7704:2021
ISO/DIS 7704:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

3.1 General terms and definitions ................................................................................................................................................... 2

3.2 Terminology of performance testing ................................................................................................................................... 3

3.3 Terminology for test microorganisms ................................................................................................................................ 4

4 Principle ........................................................................................................................................................................................................................ 6

4.1 General ........................................................................................................................................................................................................... 6

4.1.1 Batch testing ........................................................................................................................................................................ 6

4.1.2 Supplementary testing................................................................................................................................................ 7

4.2 Testing procedures .............................................................................................................................................................................. 7

4.2.1 Microbiological methods .......................................................................................................................................... 7

4.2.2 Absence of microbial contamination .............................................................................................................. 8

5 Apparatus and glassware ............................................................................................................................................................................ 8

6 Culture media and diluents ....................................................................................................................................................................... 8

7 Preparation of microorganisms for performance testing ......................................................................................... 8

7.1 General ........................................................................................................................................................................................................... 8

7.2 Reference count ...................................................................................................................................................................................... 9

7.2.1 Quantitative productivity testing....................................................................................................................... 9

7.2.2 Qualitative selectivity testing .............................................................................................................................10

7.2.3 Qualitative specificity testing .............................................................................................................................10

7.3 Preparation of a standardized test suspension using a working culture ..........................................10

7.3.1 Preparation of the test suspension (inoculum) for the test .................. ...................................10

7.4 Preparation of a test suspension using reference material ...........................................................................11

8 Sampling of membrane filters for testing................................................................................................................................11

9 Procedure..................................................................................................................................................................................................................11

9.1 General ........................................................................................................................................................................................................11

9.2 Inoculation by spread plate technique ............................................................................................................................12

9.2.1 General...................................................................................................................................................................................12

9.2.2 Inoculation .........................................................................................................................................................................12

9.3 Inoculation by membrane filtration technique ........................................................................................................12

9.3.1 General...................................................................................................................................................................................12

9.3.2 Inoculation .........................................................................................................................................................................13

9.4 Incubation and counting ..............................................................................................................................................................13

9.5 Test on absence of microbial contamination .............................................................................................................13

10 Calculation, expression and interpretation of results ................................................................................................13

10.1 General ........................................................................................................................................................................................................13

10.2 Productivity testing ..........................................................................................................................................................................14

10.3 Selectivity testing ...............................................................................................................................................................................14

10.4 Specificity testing ...............................................................................................................................................................................14

11 Documentation of test results .............................................................................................................................................................15

11.1 General ........................................................................................................................................................................................................15

11.2 Information provided by the manufacturer ................................................................................................................15

11.3 Traceability .............................................................................................................................................................................................15

Annex A (normative) Diagram of the batch testing ............................................................................................................................16

Annex B (informative) Example of card for recording test results from batch testing .................................17

© ISO 2021 – All rights reserved iii
---------------------- Page: 5 ----------------------
oSIST prEN ISO 7704:2021
ISO/DIS 7704:2021(E)

Annex C (informative) Quantitative supplementary testing of membrane filters .............................................18

Annex D (informative) Qualitative supplementary testing of membrane filters ................................................20

Annex E (informative) Practical example of quantitative batch testing and quantitative

supplementary testing by the end user .....................................................................................................................................24

Bibliography .............................................................................................................................................................................................................................33

iv © ISO 2021 – All rights reserved
---------------------- Page: 6 ----------------------
oSIST prEN ISO 7704:2021
ISO/DIS 7704:2021(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 147, Water quality, Subcommittee SC 4,

Microbiological methods.

This second edition cancels and replaces the first edition (ISO 7704:1985), which has been technically

revised.
The main changes compared to the previous edition are as follows:

— the scope has been changed to cover the requirements for the performance testing of membrane

filters used for retention and direct enumeration;

— clauses have been added for terms and definitions, microorganisms, sampling and replicates,

procedure, inoculation and incubation, counting, calculation and documentation;

— the clauses referencing culture media and diluents, test strain preparation, performance testing

and procedure have been revised to align with ISO 8199 and ISO 11133;

— Annex B has been added to give an example of card for recording test results from batch testing and

supplementary testing of membrane filters;

— Annex C has been added to describe the quantitative additional testing of membrane filters;

— Annex D has been added to describe the qualitative supplementary testing of membrane filters;

— Annex E has been added to give a practical example of batch testing and quantitative additional

testing by the end user;
— Bibliography has been added;

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 2021 – All rights reserved v
---------------------- Page: 7 ----------------------
oSIST prEN ISO 7704:2021
ISO/DIS 7704:2021(E)
Introduction

This document describes the performance testing of membrane filters used for retention followed by

direct enumeration of microorganisms by culture methods.

The main changes listed in the foreword, introduced in this document compared to ISO 7704:1985, are

considered as major.

In laboratories carrying out microbiological examinations, the main objectives are to capture,

resuscitate, grow, detect and/or enumerate a wide variety of microorganisms. Membrane filters are

used in many traditional microbiological culture techniques and are commercially available in various

brands and types. Many comparison studies of membrane filters which have been reported in the

literature show differences in their ability to recover bacteria from water samples, see References.

[18],[19],[23],[25],[27],[28],[29],[30] The complex manufacturing process means that the chemical

composition, pore size and pore structure can vary, depending on the brands, and even on the lot of

material. Furthermore, the manufacturing process can also release leachables that can potentially

interfere with the recovery of microorganisms.

Thus, it is very important to standardize the performance testing of membrane filters as much as

possible, not only to provide consistent results, but also to enable the development of standardized

procedures for enumerating specific microorganisms.
vi © ISO 2021 – All rights reserved
---------------------- Page: 8 ----------------------
oSIST prEN ISO 7704:2021
DRAFT INTERNATIONAL STANDARD ISO/DIS 7704:2021(E)
Water quality — Requirements for the performance
testing of membrane filters used for direct enumeration of
microorganisms by culture methods
1 Scope

This document specifies the requirements for the performance testing of membrane filters. This

concerns membrane filters which are used for retention followed by direct enumeration of specific

[16]

microorganisms on solid media or on other devices containing media, like absorbent pads .

It is not applicable for membrane filters used for concentration and elution or for qualitative methods.

These tests are applicable to membrane filters intended for the microbiological analysis of different

types of water, like:

— drinking water, bottled water and other types of water with expected low numbers of

microorganisms;

— water with expected higher numbers of microorganisms, for example surface water and process

water.

These tests are intended to demonstrate the suitability of the whole system - membrane filter

together with culture medium including the filtration step - required for the specific tests described in

International Standards.
This document applies to:
— manufacturers producing membrane filters;

— microbiological laboratories using membrane filters for their own testing or providing these to

other end users.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 8199:2018, Water quality — General requirements and guidance for microbiological examinations by

culture

I S O 11133:2014/A M D1: 2018 , Microbiology of food, animal feed and water — Preparation, production,

storage and performance testing of culture media
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 http:// www .iso .org ./ obp
— IEC Electropedia: available at https:// www .electropedia .org/
© ISO 2021 – All rights reserved 1
---------------------- Page: 9 ----------------------
oSIST prEN ISO 7704:2021
ISO/DIS 7704:2021(E)
3.1 General terms and definitions
3.1.1
membrane filter(s)

porous hydrophilic filtration matrix, composed of different polymers with filtration characteristics

equivalent to its/their rated nominal pore sizes, typically ranging from 0,1 µm to 1,2 µm, which is

intended to be used for retention of microorganisms

Note 1 to entry: The membrane filter assures the effective retention of microorganisms depending on the

membrane pore size when a differential (positive or negative) pressure is applied.

Note 2 to entry: The type of membrane filter to be used for a certain microbiological method is described in the

corresponding specific standard (3.1.7).
3.1.2
culture medium

formulation of substances, in liquid, semi-solid or solid form, which contain natural and/or synthetic

constituents intended to support the multiplication (with or without constituents for inhibition of

certain microorganisms), identification or preservation of viability of microorganisms

[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.3.1, modified — “constituents for” included and

Note 1 to entry has been deleted.]

Note 1 to entry: The culture medium to be used for a certain microbiological method is described in the

corresponding specific standard (3.1.7), see specific culture medium (3.1.3).
3.1.3
specific culture medium

culture medium (3.1.2), usually selective, as designated in a specific standard (3.1.7) for use with

membrane filters (3.1.1)
[7]

EXAMPLE Chromogenic Coliform Agar (CCA) used with membrane filters in accordance with ISO 9308-1 ;

[5]

Slanetz and Bartley medium used with membrane filters in accordance with ISO 7899-2 .

3.1.4
reference medium
culture medium (3.1.2) for comparative supplementary performance testing

Note 1 to entry: The reference medium is usually a non-selective culture medium (3.1.2), which is different to the

culture medium under test and demonstrated to be suitable for use in the performance testing.

EXAMPLE Tryptone soya agar (TSA) is in accordance with ISO 11133:2014/AMD1: 2018/ AMD2: 2020.

[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.3.4.13, modified — Note 1 to entry has been

implemented.]
3.1.5
batch of membrane filters
lot of membrane filters

homogeneous and fully traceable units of membrane filter (3.1.1) referring to a defined amount of bulk,

semi-finished product or end product, which is consistent in type and quality and which has been

produced within one defined production period, having been assigned the same batch (or lot) number

2 © ISO 2021 – All rights reserved
---------------------- Page: 10 ----------------------
oSIST prEN ISO 7704:2021
ISO/DIS 7704:2021(E)
3.1.6
batch of culture medium
lot of culture medium

homogeneous and fully traceable units of a culture medium (3.1.2) referring to a defined amount of

bulk, semi-finished product or end product, which is consistent in type and quality and which has been

produced within one defined production period, having been assigned the same batch (or lot) number

[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.1.2, modified — reference to 3.1.2 has been

added.]

Note 1 to entry: If the user does not define the batch or lot of culture medium used for performance testing of

membrane filters as the “end product”, it is important to demonstrate that the production process is sufficiently

controlled to produce culture media of consistent quality (for example by monitoring culture media performance

testing results).
3.1.7
specific standard

International Standard or guidance document describing the microbiological analysis of different types

of water for the detection or enumeration of a specific microorganism (or group of microorganisms)

[SOURCE: ISO 6887-1:2017, 3.10, modified]
3.2 Terminology of performance testing
3.2.1
batch testing

test of units of membrane filters (3.1.1) from a batch or a lot (3.1.5) for its/their intended use with the

specific culture medium (3.1.3) and determination of reference count (3.3.6)
3.2.2
supplementary quantitative testing

test of units of membrane filters (3.1.1) from a batch or a lot (3.1.5) for its/their intended use with the

specific culture medium (3.1.3); determination of reference count (3.3.6); test of the membrane filters on

a non-selective culture medium and test of the culture medium without membrane filter

Note 1 to entry: A detailed description of the supplementary quantitative testing is given in Annex C.

Note 2 to entry: Supplementary quantitative testing is used when a new type of a membrane filter(s) (3.1.1), or

a new manufacturer is tested initially, or when a problem in the day-to-day use or batch testing of membrane

filters is noticed.
3.2.3
performance of membrane filter

response of a membrane filter (3.1.1) challenged by a test organism (3.3.1) under defined conditions

Note 1 to entry: The defined conditions are described in the specific standard (3.1.7) for the intended use of

the membrane filter (3.1.1), like: test organism (3.3.1), specific culture medium (3.1.3), reference medium (3.1.4),

productivity (3.2.7), selectivity (3.2.6), incubation time and temperature.
3.2.4
performance of culture medium

response of a culture medium (3.1.2) challenged by a test organism (3.3.1) under defined conditions

[S OU RC E: I S O 11133:2014/A M D1: 2018/ A M D2: 2020, 3 . 2 .1]
3.2.5
productivity

level of recovery of a target microorganism (3.2.5) on the culture medium (3.1.2) with the membrane

filter (3.1.1) under defined conditions

[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.2.4, modified — adapted to the performance

testing of membrane filters.]
© ISO 2021 – All rights reserved 3
---------------------- Page: 11 ----------------------
oSIST prEN ISO 7704:2021
ISO/DIS 7704:2021(E)
3.2.6
selectivity

degree of inhibition of a non-target microorganism (3.2.6) on a selective culture medium (3.1.2) with the

membrane filter (3.1.1) under defined conditions

[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.2.5, modified — adapted to the performance

testing of membrane filters.]
3.2.7
electivity
specificity

demonstration, under defined conditions, that a non-target microorganism (3.2.6), if able to grow on

the medium, does not show the same visual characteristics as the target microorganisms (3.2.5) on the

culture medium (3.1.2) with membrane filter (3.1.1) under defined conditions

[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.2.6, modified — adapted to the performance

testing of membrane filters.]
3.3 Terminology for test microorganisms
3.3.1
target microorganism

microorganism or group of microorganisms to be detected or enumerated which should be expected

to grow under defined conditions[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.2.2] , modified

3.3.2
non-target microorganism

microorganism that is suppressed by the medium and/or conditions of incubation or does not show

expected characteristics of the target microorganism
[S OU RC E: I S O 11133:2014/A M D1: 2018/ A M D2: 2020, 3 . 2 . 3]
3.3.3
test microorganism
control strain

microorganism generally used for performance testing of membrane filters (3.1.1) and/or culture media

(3.1.2)

Note 1 to entry: Test microorganisms / control strains are further defined in accordance with their source (see

3.3.2 to 3.3.8).

[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.4.1, modified — adapted to the performance

testing of membrane filters.]
3.3.4
reference strain

microorganism obtained directly from a reference culture collection and defined to at least the species

level

Note 1 to entry: A reference culture collection is a culture collection which is a member of the World Federation

of Culture Collections (WFCC) or the European Culture Collections’ Organisation (ECCO).

Note 2 to entry: A reference strain is catalogued and described according to its characteristics and preferably

originating from water as applicable.

[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.4.2, modified — Note 1 and 2 to entry have been

implemented using modified text from shortened definition.]
4 © ISO 2021 – All rights reserved
---------------------- Page: 12 ----------------------
oSIST prEN ISO 7704:2021
ISO/DIS 7704:2021(E)
3.3.5
reference stock

set of separate identical cultures obtained by a single subculture from the reference strain (3.3.4) either

in the laboratory or from a supplier
[S OU RC E: I S O 11133:2014/A M D1: 2018/ A M D2: 2020, 3 .4 . 3]
3.3.6
stock culture
primary subculture from a reference stock (3.3.5)
[S OU RC E: I S O 11133:2014/A M D1: 2018/ A M D2: 2020, 3 .4 .4]
3.3.7
working culture

subculture from a reference stock (3.3.5) or stock culture (3.3.6) or a reference material (3.3.9) or a

certified reference material (3.3.10)

Note 1 to entry: Multi-strain reference material (3.3.9) and multi-strain certified reference material (3.3.10) can

also be used for the preparation of working cultures.

[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.4.4, modified — Note 1 to entry has been added.]

3.3.8
reference count

total count of colonies on a mostly non-selective culture medium (3.1.2) obtained without usage of a

membrane filter (3.1.1)
Note 1 to entry: For this the term “inoculum level” is often used.
3.3.9
reference material

microbiological material containing a quantity of revivable microorganisms, sufficiently homogenous

and stable with respect to the quantity of revivable microorganisms, which has been established to be

fit for its intended use in a measurement process
[12]
Note 1 to entry: See ISO Guide 30 .

[SOURCE: ISO 11133:2014/AMD1: 2018/ AMD2: 2020, 3.4.6, modified — Note 1 to entry: reference has

been updated.]
Not
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.